Published online before print March 21, 2002, 10.1148/radiol.2232010905
(Radiology 2002;223:540.)
A more recent version of this article appeared on May 1, 2002
Mucinous versus Nonmucinous Gastric Carcinoma: Differentiation with Helical CT1
Mi-Suk Park, MD,
Jeong-Sik Yu, MD,
Myeong-Jin Kim, MD,
Sang-Wook Yoon, MD,
Se Hoon Kim, MD,
Tae Woong Noh, MD,
Kwang-Hun Lee, MD,
Jong Tae Lee, MD,
Hyung Sik Yoo, MD and
Ki Whang Kim, MD
1 From the Department of Diagnostic Radiology and Research Institute of Radiological Science (M.S.P., J.S.Y., M.J.K., S.W.Y., K.H.L., J.T.L., H.S.Y., K.W.K.) and the Department of Pathology (S.H.K., T.W.N.), Yonsei Univ College of Medicine, Seoul, South Korea. Received May 10, 2001; revision requested Jun 15; revision received Aug 15; accepted Oct 8. Address correspondence to K.W.K., Department of Radiology, YongDong Severance Hosp, 146-92 Dokok-Dong, Kangnam-Ku, Seoul 135-270, South Korea (e-mail: kwkimYD@yumc.yonsei.ac.kr).
 |
ABSTRACT
|
|---|
PURPOSE: To assess the capability of helical computed tomography (CT) to assist in the differentiation between mucinous and nonmucinous gastric carcinomas, with a focus on the thickened stomach wall itself.
MATERIALS AND METHODS: In 62 patients with pathologically proved mucinous (n = 21) or nonmucinous (n = 41) gastric carcinomas, contrast material–enhanced helical CT images were obtained. The gross appearance, contrast enhancement pattern, predominant thickened layer, and degree of enhancement were retrospectively evaluated. Statistical analyses were performed with Fisher exact, 
2, and Student t tests. A P value of less than .05 was considered to indicate a statistically significant difference.
RESULTS: The most common type of gross appearance in both carcinomas was fungating: It occurred in 71% of patients with mucinous carcinomas and in 59% of patients with nonmucinous carcinomas. The next most common gross appearance type was ulcerative (24% of patients) in nonmucinous carcinomas and diffusely infiltrative (29% of patients) in mucinous carcinomas (P = .009). The most common contrast enhancement pattern was homogeneous (61% of patients) in nonmucinous carcinomas and layered (62% of patients) in mucinous carcinomas (P = .001). These findings were significantly different. The predominantly affected thickened layer was the high-attenuating inner layer or the entire layer (88% of patients) in nonmucinous carcinomas and the low-attenuating middle or outer layer (57% of patients) in mucinous carcinomas. Only two mucinous tumors showed miliary punctate calcifications in infiltrative lesions.
CONCLUSION: Helical CT may assist in distinguishing mucinous from nonmucinous gastric carcinoma, primarily on the basis of enhancement pattern, predominant layer of the thickened wall, gross appearance, and presence of calcifications.
© RSNA, 2002
Index terms: Computed tomography (CT), helical, 72.12112, 72.12114, 72.12115 • Stomach, CT, 72.12112, 72.12114, 72.12115 • Stomach, neoplasms, 72.321
|
INTRODUCTION
|
|---|
Patients with mucinous gastric carcinoma, a rare subtype of gastric carcinoma, have long been believed to have a poor prognosis (1). However, there were few comprehensive studies of mucinous gastric carcinoma until the investigations of Adachi et al (2), Wu et al (3), and Hyung et al (4). The results of these clinicopathologic studies (2–4) suggest that the overall survival rate for patients with mucinous gastric carcinoma is worse than that for patients with nonmucinous tumors because mucinous gastric carcinoma is more frequently diagnosed in the advanced stage and is associated with more frequent serosal invasion and lymphatic permeation. It is clinically useful to be able to distinguish between mucinous and nonmucinous gastric carcinomas in patients who have this cancer (3–5).
Conventionally, the role of computed tomography (CT) in the evaluation of gastric carcinoma has been to help assess for the presence or absence of lymph node or distant metastasis. CT has been considered to be unsuitable for assessment of the cancer itself (6). However, owing to the growth in popularity of helical CT used in combination with the water-filling method, CT has led to improved visualization of the gastric carcinoma tumor itself and to improved accuracy in the depiction of intramural invasion (7–9). Moreover, the excellent spatial and time resolution of helical CT has made it possible to identify the two or three normal layers of the gastric wall (9).
To our knowledge, there have been no reports of a comparison of the helical CT findings of mucinous versus nonmucinous gastric carcinomas. The purpose of our study was to assess the capability of helical CT to assist in the differentiation between mucinous and nonmucinous gastric carcinomas, with a focus on the thickened stomach wall itself.
|
MATERIALS AND METHODS
|
|---|
Patient Selection
By performing a computerized search of medical records, we identified 1,750 patients with a diagnosis of advanced gastric adenocarcinoma who underwent surgery between January 1998 and September 2000 at two institutions (YongDong Severance Hospital and Shinchon Severance Hospital, Seoul, Korea). We also searched the pathology records for the subtype of gastric carcinoma. The cancers in 68 patients fulfilled the criterion for mucinous gastric carcinoma: More than 50% of the tumor content was extracellular mucin (2). These 68 patients formed the mucinous gastric carcinoma study group. Four hundred forty-three patients with mucinous gastric carcinoma that contained intracellular mucin (signet ring–cell carcinoma) only were excluded. For comparison with the mucinous gastric carcinoma group, we systemically sampled from the remaining 1,239 patients with nonmucinous gastric carcinomas. These patients were sorted by their medical numbers, and every 10th patient was assigned to the nonmucinous gastric carcinoma study group. A total of 123 patients were selected.
Patients were further excluded from the two groups if preoperative helical CT images had not been obtained. Preoperative helical CT images had been obtained in 21 patients with mucinous gastric carcinoma and in 41 patients with nonmucinous gastric carcinoma. Thus, our retrospective study population included 21 patients (16 men, five women; mean age, 53.8 years; age range, 34–82 years) with mucinous carcinoma and 41 patients (28 men, 13 women; mean age, 60 years; age range, 37–75 years) with nonmucinous carcinoma. The institutional review boards at the two hospitals do not require their approvals or informed patient consent for review of the medical records, files, and images.
CT Technique
All CT examinations were performed with a helical scanner (HiSpeed CT/i, GE Medical Systems, Milwaukee, Wis; or Somatom Plus S, Siemens, Erlangen, Germany). Each patient fasted for 6 hours before undergoing CT. The patients drank 400–600 mL of pure tap water immediately before undergoing scanning. Five of the 62 patients, one in the mucinous cancer group and four in the nonmucinous cancer group, were unable to drink water. However, it was still possible to assess the gastric wall in these five patients because of the adequate distention of the stomach due to gastric outlet obstruction. Neither anticholinergic agents nor glucagon was administered. A total of 120 mL of iopromide (Ultravist; Schering, Berlin, Germany) was administered intravenously at a rate of 2.5 mL/sec by using an automatic power injector. At one institution (20 patients), biphasic helical CT scans were obtained 35 seconds (arterial dominant phase) and 75 seconds (parenchymal phase) after the initiation of the intravenous contrast material injection. At the other institution (42 patients), monophasic helical CT scans were obtained 70 seconds (parenchymal phase) after the initiation of the contrast material injection. We evaluated only the CT images obtained during the parenchymal phase. The upper part of the abdomen from the level of the hepatic dome to the iliac crest was scanned during the helical mode with 7-mm collimation, a pitch of 1.5, and 7-mm reconstruction intervals.
Imaging and Histopathologic Analyses
Three board-certified abdominal radiologists (M.S.P., J.S.Y., S.W.Y.) collectively and retrospectively reviewed the helical CT scans obtained in the 62 patients in consensus, without knowledge of the pathologic subtype of the gastric carcinoma. The gross appearance, contrast enhancement pattern, degree of enhancement, predominant thickened wall layer, and ratio of high-attenuating inner layer thickness to total thickness were evaluated. Gross appearance was classified as one of four types: (a) polypoid, defined as an intraluminal growing mass; (b) fungating, defined as a lesion with a focal wall thickening of more than 1 cm, with or without a depressed area; (c) ulcerated, defined as a depressed lesion with a wall thickening of less than 1 cm; or (d) diffusely infiltrative, defined as a lesion involving more than 50% of the entire stomach wall (10). We modified the Borrmann classification of advanced gastric carcinoma to adjust for the appearance of the tumors on CT scans.
The contrast enhancement patterns on postcontrast CT images were recorded as (a) homogeneous, (b) heterogeneous, or (c) layered, which was defined as diffuse thickening of the gastric wall with more than 50% preservation of a multilayered pattern. The degree of enhancement was graded as follows: (a) high, or tumor attenuation higher than that of the liver; (b) moderate, or tumor attenuation between that of the liver and that of muscle; or (c) low, or tumor attenuation lower than that of muscle. The thickness of the tumor was measured at the thickest point of the most thickened wall, and the predominant thickened layer was recorded. In the cases of a layered pattern, the ratio of high-attenuating inner layer thickness to total thickness also was calculated. Other associated findings, such as calcification, also were evaluated.
The histopathologic findings in surgical specimens from all of the patients were retrospectively reviewed by two pathologists (S.H.K., T.W.N.), with special emphasis on the mucin content of the mucinous carcinomas, the predominantly affected wall layer, and any other frequent findings. One radiologist (M.S.P.) and the two pathologists correlated the CT findings with the histopathologic findings by means of a layer-to-layer comparison.
We compared the gross appearances of the mucinous and nonmucinous gastric carcinomas at CT by using the two-tailed Fisher exact test. We compared the contrast enhancement patterns of both types of carcinoma by using the 2 test. The total thickness of the tumors and the ratio of high-attenuating inner layer thickness to total thickness (in the cases of a layered pattern) were compared between the mucinous and nonmucinous gastric carcinomas by means of the Student t test. A P value of less than .05 was considered to indicate a statistically significant difference.
|
RESULTS
|
|---|
Our comparison of the gross appearances of mucinous and nonmucinous gastric carcinomas at CT is illustrated in Figure 1. The most common type of gross appearance at CT was fungating (Figs 1–5) in both gastric carcinoma groups: in 15 (71%) of 21 patients with mucinous cancers and in 24 (59%) of 41 patients with nonmucinous cancers. No polypoid or ulcerated types were observed in mucinous carcinomas. A diffusely infiltrative gross appearance (Figs 6, 7) was seen more often in mucinous carcinomas (six [29%] patients) than in nonmucinous carcinomas (four [10%] patients). All of the mucinous tumors manifested with focal or diffuse wall thickening. In the nonmucinous tumors, all four types of gross appearance were seen. Ulcerated was the second most common (in 10 [24%] patients) type of gross appearance in nonmucinous tumors (Fig 8), whereas it was not seen in mucinous tumors. The gross appearances of the two types of carcinoma were significantly different at statistical analysis (P = .009).
View larger version (25K):
[in this window]
[in a new window]
|
Figure 1. Graph illustrates differences in gross appearance between the mucinous and nonmucinous gastric carcinomas on helical CT scans. The mucinous tumors had a fungating or diffusely infiltrative appearance; none had an ulcerated or polypoid appearance. The nonmucinous tumors had all four types of gross appearance.
|
|
View larger version (121K):
[in this window]
[in a new window]
|
Figure 2a. Fungating mucinous gastric carcinoma in an 82-year-old man. (a) Transverse contrast material-enhanced helical CT scan obtained during the parenchymal phase shows focal wall thickening (arrowheads), particularly in the low-attenuating outer layer, with more than 50% preservation of the thin high-attenuating inner layer (arrows). The layered enhancement pattern is shown. (b) Low-power photomicrograph shows large mucin pools (M) mainly in the submucosal and proper muscle layers, with focal extension into the mucosal layer. Most of the overlying normal mucosa (arrows), which corresponds to the thin high-attenuating inner layer seen in a, is preserved.
|
|
View larger version (96K):
[in this window]
[in a new window]
|
Figure 2b. Fungating mucinous gastric carcinoma in an 82-year-old man. (a) Transverse contrast material-enhanced helical CT scan obtained during the parenchymal phase shows focal wall thickening (arrowheads), particularly in the low-attenuating outer layer, with more than 50% preservation of the thin high-attenuating inner layer (arrows). The layered enhancement pattern is shown. (b) Low-power photomicrograph shows large mucin pools (M) mainly in the submucosal and proper muscle layers, with focal extension into the mucosal layer. Most of the overlying normal mucosa (arrows), which corresponds to the thin high-attenuating inner layer seen in a, is preserved.
|
|
View larger version (105K):
[in this window]
[in a new window]
|
Figure 3a. Fungating mucinous gastric carcinoma in a 62-year-old man. (a) Transverse contrast-enhanced helical CT scan obtained during the parenchymal phase shows focal wall thickening (arrows), particularly in the low-attenuating outer layer. The thickening of the high-attenuating inner layer (arrowheads) is irregular. (b) Low-power photomicrograph shows large mucin pools (M) mainly in the submucosal and proper muscle layers, with focal extension into the inner and outer surfaces (arrowheads). The malignant cell groups (arrows) at the mucosal surface correspond to the thin high-attenuating inner layer seen in a.
|
|
View larger version (121K):
[in this window]
[in a new window]
|
Figure 3b. Fungating mucinous gastric carcinoma in a 62-year-old man. (a) Transverse contrast-enhanced helical CT scan obtained during the parenchymal phase shows focal wall thickening (arrows), particularly in the low-attenuating outer layer. The thickening of the high-attenuating inner layer (arrowheads) is irregular. (b) Low-power photomicrograph shows large mucin pools (M) mainly in the submucosal and proper muscle layers, with focal extension into the inner and outer surfaces (arrowheads). The malignant cell groups (arrows) at the mucosal surface correspond to the thin high-attenuating inner layer seen in a.
|
|
View larger version (106K):
[in this window]
[in a new window]
|
Figure 4a. Fungating nonmucinous gastric carcinoma in a 69-year-old woman. (a) Transverse contrast-enhanced helical CT scan obtained during the parenchymal phase shows focal gastric wall thickening of mainly the strongly enhancing, irregularly thickened inner layer (arrows). The attenuation of the thickened inner layer is higher than that of the liver. The heterogeneous enhancement pattern is shown. (b) Low-power photomicrograph shows a protruded tumor mass (T) mainly at the mucosal layer, with focal extension into the submucosal layer (arrows). In another area, the carcinoma cells are extending into the muscle and serosal layer (not shown).
|
|
View larger version (104K):
[in this window]
[in a new window]
|
Figure 4b. Fungating nonmucinous gastric carcinoma in a 69-year-old woman. (a) Transverse contrast-enhanced helical CT scan obtained during the parenchymal phase shows focal gastric wall thickening of mainly the strongly enhancing, irregularly thickened inner layer (arrows). The attenuation of the thickened inner layer is higher than that of the liver. The heterogeneous enhancement pattern is shown. (b) Low-power photomicrograph shows a protruded tumor mass (T) mainly at the mucosal layer, with focal extension into the submucosal layer (arrows). In another area, the carcinoma cells are extending into the muscle and serosal layer (not shown).
|
|
View larger version (117K):
[in this window]
[in a new window]
|
Figure 5a. Fungating nonmucinous gastric carcinoma in a 51-year-old man. (a) Transverse contrast-enhanced helical CT scan obtained during the parenchymal phase shows focal wall thickening (arrows) with depression (arrowheads) at the posterior wall of the gastric antrum. The wall is homogeneously and strongly enhancing. (b) Low-power photomicrograph shows malignant cell groups (T) in solid sheets with ulceration (arrows).
|
|
View larger version (82K):
[in this window]
[in a new window]
|
Figure 5b. Fungating nonmucinous gastric carcinoma in a 51-year-old man. (a) Transverse contrast-enhanced helical CT scan obtained during the parenchymal phase shows focal wall thickening (arrows) with depression (arrowheads) at the posterior wall of the gastric antrum. The wall is homogeneously and strongly enhancing. (b) Low-power photomicrograph shows malignant cell groups (T) in solid sheets with ulceration (arrows).
|
|
View larger version (113K):
[in this window]
[in a new window]
|
Figure 6a. Diffusely infiltrative mucinous gastric carcinoma in a 36-year-old man. (a) Transverse contrast-enhanced helical CT scan obtained during the parenchymal phase shows a diffusely thickened, low-attenuating gastric wall with miliary punctate calcifications (arrows). (b) Gross specimen shows a tumor mass (T) with punctate calcifications (arrows). (c) Low-power photomicrograph shows mucin pools (M) that have replaced the entire stomach wall, with extension into the inner and outer surfaces. Neither overlying normal mucosa nor malignant cell groups are seen. Hemorrhage (arrowheads) and calcifications (arrows) also are seen.
|
|
View larger version (48K):
[in this window]
[in a new window]
|
Figure 6b. Diffusely infiltrative mucinous gastric carcinoma in a 36-year-old man. (a) Transverse contrast-enhanced helical CT scan obtained during the parenchymal phase shows a diffusely thickened, low-attenuating gastric wall with miliary punctate calcifications (arrows). (b) Gross specimen shows a tumor mass (T) with punctate calcifications (arrows). (c) Low-power photomicrograph shows mucin pools (M) that have replaced the entire stomach wall, with extension into the inner and outer surfaces. Neither overlying normal mucosa nor malignant cell groups are seen. Hemorrhage (arrowheads) and calcifications (arrows) also are seen.
|
|
View larger version (109K):
[in this window]
[in a new window]
|
Figure 6c. Diffusely infiltrative mucinous gastric carcinoma in a 36-year-old man. (a) Transverse contrast-enhanced helical CT scan obtained during the parenchymal phase shows a diffusely thickened, low-attenuating gastric wall with miliary punctate calcifications (arrows). (b) Gross specimen shows a tumor mass (T) with punctate calcifications (arrows). (c) Low-power photomicrograph shows mucin pools (M) that have replaced the entire stomach wall, with extension into the inner and outer surfaces. Neither overlying normal mucosa nor malignant cell groups are seen. Hemorrhage (arrowheads) and calcifications (arrows) also are seen.
|
|
View larger version (99K):
[in this window]
[in a new window]
|
Figure 7a. Diffusely infiltrative nonmucinous gastric carcinoma in a 57-year-old man. (a) Transverse contrast-enhanced helical CT scan obtained during the parenchymal phase shows a strongly enhancing, diffusely thickened gastric wall (T). The homogeneous enhancement pattern is shown. (b) Low-power photomicrograph shows malignant cell groups (T) in solid sheets that have replaced the entire stomach wall, with extension into the inner and outer surfaces.
|
|
View larger version (93K):
[in this window]
[in a new window]
|
Figure 7b. Diffusely infiltrative nonmucinous gastric carcinoma in a 57-year-old man. (a) Transverse contrast-enhanced helical CT scan obtained during the parenchymal phase shows a strongly enhancing, diffusely thickened gastric wall (T). The homogeneous enhancement pattern is shown. (b) Low-power photomicrograph shows malignant cell groups (T) in solid sheets that have replaced the entire stomach wall, with extension into the inner and outer surfaces.
|
|
View larger version (111K):
[in this window]
[in a new window]
|
Figure 8a. Ulcerated nonmucinous gastric carcinoma in a 60-year-old woman. (a) Transverse contrast-enhanced transverse helical CT scan obtained during the parenchymal phase shows a depressed lesion (curved arrow) with focal thickening (straight arrows) of less than 1 cm at the posterior wall of the gastric body. The enhancement of the lesion is greater than that of the normal mucosa. (b) Gross specimen shows a malignant ulcer (arrows).
|
|
View larger version (129K):
[in this window]
[in a new window]
|
Figure 8b. Ulcerated nonmucinous gastric carcinoma in a 60-year-old woman. (a) Transverse contrast-enhanced transverse helical CT scan obtained during the parenchymal phase shows a depressed lesion (curved arrow) with focal thickening (straight arrows) of less than 1 cm at the posterior wall of the gastric body. The enhancement of the lesion is greater than that of the normal mucosa. (b) Gross specimen shows a malignant ulcer (arrows).
|
|
The contrast enhancement patterns of the two types of carcinoma were significantly different (P = .001) (Fig 9). The most common (in 13 [62%] patients) contrast enhancement pattern in mucinous tumors was the layered type (Figs 2, 3), whereas the most common (in 25 [61%] patients) pattern in nonmucinous tumors was the homogeneous type (Figs 5, 7). In mucinous tumors, the predominantly thickened layer was the middle or outer layer, which had low attenuation, and the thin high-attenuating inner layer was preserved (in 12 [57%] patients) (Figs 2, 3). Histopathologically, the thickened low-attenuating middle or outer layer was the mucin pool, which was located mainly in the submucosa or deeper layer, and the thin high-attenuating inner layer was either the overlying normal mucosa (Fig 2) or columns of malignant cells (Fig 3).
View larger version (23K):
[in this window]
[in a new window]
|
Figure 9. Graph illustrates differences in contrast enhancement pattern between the mucinous and nonmucinous gastric carcinomas on parenchymal phase helical CT scans. The most common enhancement pattern was layered in the mucinous tumors and homogeneous in the nonmucinous tumors.
|
|
In nonmucinous tumors, the predominantly thickened layer was either the inner layer (Fig 4) or the entire layer (Figs 5, 7), either of which had high attenuation (in 36 [88%] patients). Histopathologically, the strongly enhancing thickened layer was the malignant cell group in a tubular formation or in solid sheets (Figs 4, 5, 7).
The tumor thickness of the nonmucinous gastric carcinomas ranged from 0.7 to 6.8 cm (mean, 1.7 cm); and the tumor thickness of the mucinous carcinomas, from 1.2 to 2.1 cm (mean, 1.5 cm). Differences in tumor thickness were not statistically significant (P = .26). In the cases of a layered contrast enhancement pattern, the ratio of high-attenuating inner layer thickness to total thickness was significantly higher in the nonmucinous tumors (range, 0.11–0.65; mean, 0.38) compared with that in the mucinous tumors (range, 0.07–0.60; mean, 0.22) (P = .05). Only two mucinous tumors showed miliary punctate calcifications in the infiltrative lesions (Fig 6).
|
DISCUSSION
|
|---|
Mucinous gastric carcinoma has been termed mucoid, colloid, or gelatinous carcinoma (3). It is a rare subtype of gastric carcinoma that represents approximately 3%–5% of all gastric epithelial cancers (2–5). Previously, however, there was no criterion for classifying the mucin-producing form of this tumor, and no distinction between those with intracellular mucin and those with extracellular mucin was made (1,3). The World Health Organization classifies gastric carcinoma into four types—(a) papillary, (b) tubular, (c) mucinous, and (d) signet ring cell—and defines mucinous gastric carcinoma as "an adenocarcinoma in which a substantial amount of extracellular mucin (more than 50% of the tumor) is retained within the tumor" (11).
The relationship between the World Health Organization histologic classification of this carcinoma and the prognosis has been considered controversial. However, the results of some comprehensive clinicopathologic studies that have been published in the past 5 years have indicated that mucinous gastric carcinoma, as compared with nonmucinous gastric carcinoma (ie, tubular and papillary adenocarcinomas), has an unfavorable prognosis (3,4). Wu et al (3) reported a 5-year survival rate of 18% with mucinous gastric carcinoma and of 37% with nonmucinous carcinoma; these rates are significantly different. These investigators suggested that the poor prognosis associated with mucinous gastric carcinoma is due to the more advanced stage of the disease at diagnosis and the frequent serosal involvement and not to the mucinous histologic content itself. However, the reason that mucinous carcinoma is diagnosed at a later stage is not fully understood.
The ability to distinguish mucinous from nonmucinous gastric carcinomas on the basis of the CT imaging characteristics of these tumors is clinically important because CT is the imaging technique that is most frequently used for staging of gastric carcinomas. Helical CT used in combination with the water-filling method has led to a marked improvement in the detection and characterization of gastric carcinoma (7–9). Takao et al (12) reported the accuracies of helical CT in the detection and staging of advanced gastric carcinoma to be 98% and 82%, respectively. Moreover, the excellent spatial resolution of helical CT makes it possible to identify the triple-layer structure of the gastric wall that corresponds to the histopathologic structures: The inner layer with high attenuation corresponds to the mucosa and the muscular layer of the mucosa; the middle layer with low attenuation, to the submucosal layer that consists of coarse and fatty tissues; and the outer layer with slightly high attenuation, to the proper muscle with serosa (9). The focus of our study was to evaluate the helical CT findings of the thickened stomach wall itself so that we could distinguish mucinous from nonmucinous gastric carcinomas.
The enhancement pattern and the most thickened layer differed between the mucinous and nonmucinous gastric carcinomas. The most common enhancement pattern of the nonmucinous carcinomas was the homogeneous type, and the attenuation was high, reflecting the enhancement of the malignant cell group, which was located within the entire wall without layering. Aside from the nonmucinous carcinomas with these characteristics, most of the remaining nonmucinous tumors showed a thickening of the inner layer, which had similar or greater enhancement than the liver and corresponded to malignant cell groups located primarily in the mucosal layer and extending into the deeper layer.
On the other hand, most of the mucinous gastric carcinomas in our study showed a thickening of the diffusely low-attenuating middle or outer layer, which corresponded to the mucin pool located primarily in the submucosa or deeper layer. These structures facilitate the intramural accumulation of mucin that is seen in pathologic specimens. The enhancing portion of the mucinous carcinoma was either the overlying normal mucosa or columns of malignant cells, which produce the layering enhancement pattern. Histopathologically, mucinous carcinoma comprises large pools of extracellular mucin that are sparsely lined by columns of malignant cells, cords, and vessels (13). On helical CT scans, the mucin pools are not enhancing and have very low attenuation, whereas the malignant cell groups are strongly enhancing and have very high attenuation. The helical CT features of both types of gastric carcinoma correspond closely to the histopathologic compositions of the tumors.
The gross appearances of mucinous and nonmucinous carcinomas were different. The most common appearance was the fungating type, which manifested as focal wall thickening in both types of gastric carcinoma. However, the second most common gross appearance was the ulcerated type in the nonmucinous tumors and the diffusely infiltrative type in the mucinous tumors. There were no ulcerated lesions in the mucinous carcinomas, probably because the mucin pool that appears as a thickened wall on CT scans must exist in mucinous tumors. The total wall thickness of all of the mucinous tumors in this study was greater than 1 cm. Therefore, an ulcerated appearance of gastric carcinoma without a thickened wall may rule out mucinous carcinoma. The relatively high prevalence of the diffusely infiltrative appearance of mucinous carcinomas may be explained by the diffuse intramural spread of mucin primarily along the submucosal layer. No mucinous carcinomas had the polypoid appearance on CT scans in our study. The polypoid appearance was rare, even among the nonmucinous carcinomas, so the absence of this appearance among the mucinous carcinomas may have been due to the small number of patients with mucinous carcinomas in our study.
In our study, calcifications were present in only the mucinous carcinomas, even though the number of patients with these tumors was small. Two of the 21 patients with mucinous carcinomas had tumors that contained calcifications with a punctate, miliary pattern. However, no calcifications were observed in any of the nonmucinous carcinomas in our study. Our study results agree with those of previous case reports of mucinous gastric carcinoma (14–16). Leiomyoma and leiomyosarcoma sometime have calcifications on CT scans, but these calcifications are usually circumscribed and patchy, without diffuse distribution (15). Therefore, diffusely distributed miliary punctate calcifications in gastric tumors may favor mucinous adenocarcinoma (14,15).
A limitation of our study is that we evaluated only those CT images that were obtained during the parenchymal phase, so we were unable to analyze dynamic changes in enhancement patterns. Takao et al (12) reported that the multilayered pattern of the normal gastric wall was most clearly demonstrated at CT during the arterial dominant phase in 50% of cases and at CT during the parenchymal phase in 32% of cases and that this pattern was clearly demonstrated during the arterial dominant and parenchymal phases equally in another 18% of cases. However, because we were unable to obtain arterial dominant phase CT images in all patients, we evaluated only the parenchymal phase images, which were available for all of the patients in our study. According to our experiences, the multilayered pattern of the normal gastric wall is clearly demonstrated during the parenchymal phase also.
In conclusion, we observed statistically significant differences in helical CT findings between the patients with mucinous gastric carcinomas and those with nonmucinous gastric carcinomas. A diffusely thickened, very low-attenuating middle or outer layer and preservation of the thin high-attenuating inner layer can be helpful findings that suggest mucinous gastric carcinoma.
|
FOOTNOTES
|
|---|
Author contributions: Guarantor of integrity of entire study, M.S.P.; study concepts, M.S.P., K.W.K.; study design, M.S.P., J.S.Y.; literature research, M.S.P.; clinical studies, M.J.K., J.T.L., H.S.Y., S.H.K., T.W.N.; data acquisition, M.S.P.; data analysis/interpretation, S.W.Y., K.H.L.; statistical analysis, M.S.P.; manuscript preparation and editing, M.S.P.; manuscript definition of intellectual content, M.S.P., J.S.Y.; manuscript revision/review, J.S.Y.; manuscript final version approval, K.W.K.
|
REFERENCES
|
|---|
- Hoerr SO, Hazard JB, Bailey D. Prognosis in carcinoma of the stomach in relation to microscopic type. Surg Gynecol Obstet 1966; 122:485-494.
- Adachi Y, Mori M, Kido A, Shimono R, Maehara Y, Sugimachi K. A clinicopathologic study of mucinous gastric carcinoma. Cancer 1992; 69:866-871.
- Wu CY, Yeh HZ, Shih RTP, Chen GH. A clinicopathologic study of mucinous gastric carcinoma including multivariate analysis. Cancer 1998; 83:1312-1318.
- Hyung WJ, Noh SH, Shin DW, et al. Clinicopathologic characteristics of mucinous gastric adenocarcinoma. Yonsei Med J 1999; 40:99-106.
- Songür Y, Okai T, Watanabe H, Fujii T, Motoo Y, Sawabu N. Preoperative diagnosis of mucinous gastric adenocarcinoma by endoscopic ultrasonography. Am J Gastroenterol 1996; 91:1586-1590.
- Balfe DM, Koehler RE, Karstaedt M, Stanley RJ, Sagel SS. Computed tomography of gastric neoplasms. Radiology 1981; 140:431-436.
- Dux M, Richter GM, Hansmann J, Kuntz C, Kauffmann GW. Helical hydro-CT for diagnosis and staging of gastric carcinoma. J Comput Assist Tomogr 1999; 23:913-922.
- Sohn KM, Lee JM, Lee SY, Ahn BY, Park SM, Kim KM. Comparing MR imaging and CT in the staging of gastric carcinoma. AJR Am J Roentgenol 2000; 174:1551-1557.
- Kadowaki K, Murakami T, Yoshioka H, et al. Helical CT imaging of gastric cancer: normal wall appearance and the potential for staging. Radiat Med 2000; 18:47-54.
- Lechago J, Genta RM. Stomach and duodenum. In: Damjanor I, Linder J, eds. Anderson’s pathology. 10th ed. St Louis, Mo: Mosby–Year Book, 1996; 1661-1707.
- Watanabe H, Jass JR, Sobin LH. Histological typing of esophageal and gastric tumours 2nd ed. WHO international histological classification of tumors. Berlin, Germany: Springer-Verlag, 1990; 1-26.
- Takao M, Fukuda T, Iwanaga S, et al. Gastric cancer: evaluation of triphasic spiral CT and radiologic-pathologic correlation. J Comput Assist Tomogr 1998; 22:288-294.
- Teixeira CR, Tanaka S, Haruma K, et al. The clinical significance of the histologic subclassification of colorectal carcinoma. Oncology 1993; 50:495-499.
- Nishimura K, Togashi K, Tohdo G, et al. Computed tomography of calcified gastric carcinoma. J Comput Assist Tomogr 1984; 8:1010-1011.
- Libson E, Bloom RA, Blank P, Emerson DS. Calcified mucinous adenocarcinoma of the stomach: the CT appearance. J Comput Assist Tomogr 1985; 9:255-258.
- Miyake H, Maeda H, Kurauchi S, Watanabe H, Kawaguchi M, Tsuji K. Thickened gastric walls showing diffuse low attenuation on CT. J Comput Assist Tomogr 1989; 13:253-255.
This article has been cited by other articles:
|
|
|
|
 
K. Shimizu, K. Ito, N. Matsunaga, A. Shimizu, and Y. Kawakami
Diagnosis of Gastric Cancer with MDCT Using the Water-Filling Method and Multiplanar Reconstruction: CT-Histologic Correlation
Am. J. Roentgenol.,
November 1, 2005;
185(5):
1152 - 1158.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M.-S. Park, H. K. Ha, B. S. Choi, K. W. Kim, S.-J. Myung, A. Y. Kim, T. K. Kim, P. N. Kim, N.-J. Lee, J. K. Lee, et al.
Scirrhous Gastric Carcinoma: Endoscopy versus Upper Gastrointestinal Radiography
Radiology,
May 1, 2004;
231(2):
421 - 426.
[Abstract]
[Full Text]
[PDF]
|
|
|
TOP
ABSTRACT
INTRODUCTION
