DOI: 10.1148/radiol.2481050321
(Radiology 2008;248:314-316.)
© RSNA, 2008
Case 135: Presacral Myelolipoma1
Phoebe H. Dann, MD,
Glenn A. Krinsky, MD and
Gary M. Israel, MD
1 From the Department of Radiology, New York University Medical Center, New York, NY (P.H.D., G.M.I.); and Department of Radiology, the Valley Hospital, Ridgewood, NJ (G.A.K.). Received February 24, 2005; revision requested April 21; revision received June 1; final version accepted June 21.
Address correspondence to G.M.I., Department of Diagnostic Radiology, Yale University School of Medicine, PO Box 208042, 333 Cedar St, New Haven, CT 06520-8042 (e-mail: gary.israel{at}yale.edu).
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HISTORY
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An 82-year-old woman presented with a history of coronary artery disease and lower abdominal pain of 3 months duration. Computed tomography (CT) was used to examine the abdomen and pelvis.
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IMAGING FINDINGS
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Two axial CT images (Fig 1) showed a 4.5 x 3.5-cm well-defined heterogeneous presacral mass that was in direct contiguity with the sacrum but did not invade it. The mass was predominately composed of soft tissue, but macroscopic fat was present within it.
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Figure 1a: Axial CT images of the pelvis obtained at the level of the (a) midsacrum and (b) lower sacrum with intravenous (100 mL of iohexol, Omnipaque; GE Healthcare, Milwaukee, Wis) and oral (900 mL of 2% iohexol, Omnipaque) contrast material show a 4.5 x 3.5-cm well-defined heterogeneous presacral mass that is in direct contiguity with the sacrum but does not invade it. The mass is predominately composed of soft tissue; however, macroscopic fat (arrows) is present within it.
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Figure 1b: Axial CT images of the pelvis obtained at the level of the (a) midsacrum and (b) lower sacrum with intravenous (100 mL of iohexol, Omnipaque; GE Healthcare, Milwaukee, Wis) and oral (900 mL of 2% iohexol, Omnipaque) contrast material show a 4.5 x 3.5-cm well-defined heterogeneous presacral mass that is in direct contiguity with the sacrum but does not invade it. The mass is predominately composed of soft tissue; however, macroscopic fat (arrows) is present within it.
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DISCUSSION
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The imaging findings were most consistent with a diagnosis of presacral myelolipoma. While this disease is found most commonly in the adrenal glands, there have been at least 43 reported cases of extraadrenal myelolipomas, about half of which occurred in a presacral location (1). Extraadrenal myelolipomas are benign and are identical to adrenal myelolipomas at histologic analysis. They contain mature adipose cells and trilineage hematopoietic cells (red blood cells, white blood cells, and platelets) in distributions that are identical to those of normal bone marrow (2,3). Other extraadrenal locations include the perirenal retroperitoneum, mediastinum, liver, and stomach (1,2,4).
Presacral myelolipomas classically occur in older patients, with a female predominance of approximately 2:1 (4). Usually, they are asymptomatic and incidentally discovered; however, they may cause symptoms from mass effect on adjacent structures, including the bladder, ureters, sacral nerve plexus, and rectum (2,4,5). They are not associated with hematologic disturbances; however, they have been associated with Cushing syndrome, Addison disease, adrenal hyperplasia, and chronic exogenous steroid use (4).
Presacral myelolipomas are typically well-encapsulated round or oval masses that can vary in size (4). (Masses up to 26 cm in diameter have been described.) They may contain varying amounts of fat and interspersed soft-tissue elements that may enhance after contrast material administration. Small areas of hemorrhage within the mass can calcify, and they can adhere to the sacrum without bone invasion (1,2,6).
The characteristic finding of a presacral myelolipoma (besides its location) is the presence of fat within the mass, which would appear lucent on conventional radiographs, hyperechoic on ultrasonographic images (7), and hypovascular on conventional angiograms (8). However, the fatty tissue within a myelolipoma can be definitively diagnosed with only CT or magnetic resonance (MR) imaging. At CT, this tissue would be of low attenuation (
–20 HU), while at MR imaging, it would have increased signal intensity at T1-weighted sequences and decreased signal intensity at fat-suppressed T1-weighted sequences (Fig 2) (1,9).
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Figure 2a: MR images obtained in a 63-year-old woman with a presacral myelolipoma. (a) Axial T1-weighted image (repetition time msec/echo time msec, 180/4.6; flip angle, 90°) shows a well-defined presacral soft-tissue mass that does not invade the sacrum. The portion of the mass that is hyperintense (arrow) could be secondary to blood products or fat. (b) Axial fat-suppressed gadolinium-enhanced (0.1 mmol/kg gadopentetate dimeglumine, Magnevist; Bayer Healthcare, Wayne, NJ) T1-weighted image (4.6/1.4; flip angle, 12°) shows that the portion of the mass that was hyperintense in a is now hypointense. This finding is diagnostic of macroscopic fat. The mass was resected, and presacral myelolipoma was diagnosed.
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Figure 2b: MR images obtained in a 63-year-old woman with a presacral myelolipoma. (a) Axial T1-weighted image (repetition time msec/echo time msec, 180/4.6; flip angle, 90°) shows a well-defined presacral soft-tissue mass that does not invade the sacrum. The portion of the mass that is hyperintense (arrow) could be secondary to blood products or fat. (b) Axial fat-suppressed gadolinium-enhanced (0.1 mmol/kg gadopentetate dimeglumine, Magnevist; Bayer Healthcare, Wayne, NJ) T1-weighted image (4.6/1.4; flip angle, 12°) shows that the portion of the mass that was hyperintense in a is now hypointense. This finding is diagnostic of macroscopic fat. The mass was resected, and presacral myelolipoma was diagnosed.
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It may be difficult to distinguish presacral myelolipoma from liposarcoma, teratoma, extramedullary hematopoiesis, or neurogenic tumor (1,2,5,10,11). A combination of the imaging findings and the clinical scenario might be helpful in this differentiation. The most common fat-containing retroperitoneal tumor is well-differentiated liposarcoma (5,11), which typically does not have a capsule, is poorly marginated with irregular contours, and exhibits an infiltrative growth pattern (2). Extramedullary hematopoietic tissue is usually multifocal, occurs in patients with underlying hematologic disease, and typically does not contain fat (1,10). Some neurogenic tumors—such as sacrococcygeal chordomas—typically cause aggressive bone destruction and symptoms that include pain, swelling, and neurologic defects (12), while other tumors—such as neurofibromas—slowly remodel the bone and may extend into the sacral foramina. Sacrococcygeal teratomas are classically noted at birth and can be associated with vertebral anomalies.
However, there is overlap in the appearance of these different entities; therefore, they cannot be distinguished with imaging alone. Even so, myelolipomas are histologically distinct and sometimes can be differentiated from other fat-containing lesions with needle biopsy (1,4,6,10,11). When compared with myelolipomas, liposarcomas lack areas of hemorrhage and contain lipoblasts and zones of cellular atypia (11). Neurogenic tumors contain neural elements that are not present in myelolipomas. Teratomas and mesenchymal tumors may contain hematopoietic tissue and fat (similar to myelolipomas); however, they also contain other tissue subtypes (1).
Since presacral myelolipoma is benign and does not necessarily warrant surgical resection, percutaneous biopsy can be helpful in differentiating it from other presacral masses. However, if the patient is symptomatic or if the mass cannot be definitively diagnosed at needle biopsy, surgical resection may be necessary.
This patient had classic features of presacral myelolipoma. She was an older woman who had a well-defined and encapsulated presacral soft-tissue mass that contained macroscopic fatty components. Although the mass was in direct contiguity with the sacrum, it did not destroy or invade the sacrum. Even though the mass was thought to represent a presacral myelolipoma, a liposarcoma could not be excluded on the basis of the imaging findings alone. It was believed that the mass was contributing to the patient's symptoms; therefore, percutaneous biopsy was not requested and surgical resection was performed.
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FOOTNOTES
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Part one of this case appeared 4 months previously and may contain larger images.
Authors stated no financial relationship to disclose.
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References
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- Kammen BF, Elder DE, Fraker DL, Siegelman ES. Extraadrenal myelolipoma: MR imaging findings. AJR Am J Roentgenol 1998;171:721–723.[Free Full Text]
- Sutker B, Balthazar EJ, Fazzini E. Presacral myelolipoma: CT findings. J Comput Assist Tomogr 1985;9:1128–1130.[Medline]
- Saboorian MH, Timmerman TG, Ashfaq R, Maiese RL. Fine-needle aspiration of a presacral myelolipoma: a case presentation with flow cytometry and immunohistochemical studies. Diagn Cytopathol 1999;20:47–51.[CrossRef][Medline]
- Singla AK, Kechejian G, Lopez MJ. Giant presacral myelolipoma. Am Surg 2003;69:334–338.[Medline]
- Prahlow JA, Loggie BW, Cappellari JO, Scharling ES, Teot LA, Iskandar SS. Extra-adrenal myelolipoma: report of two cases. South Med J 1995;88:639–643.[CrossRef][Medline]
- Rao P, Kenney PJ, Wagner BJ, Davidson AJ. Imaging and pathologic features of myelolipoma. RadioGraphics 1997;17:1373–1385.[Abstract]
- Asch MR, Poon PY, McCallum RW, et al. Myelolipoma: radiologic findings in seven patients. J Can Assoc Radiol 1989;40:247–250.
- Chen KT, Felix EL, Flam MS. Extraadrenal myelolipoma. Am J Clin Pathol 1982;79:386–389.
- Cyran KM, Kenney PJ, Memel DS, Yacoub I. Adrenal myelolipoma. AJR Am J Roentgenol 1996;166:395–400.[Abstract/Free Full Text]
- Kenney PJ, Wagner BJ, Rao P, Heffess CS. Myelolipoma: CT and pathologic features. Radiology 1998;208:87–95.[Abstract/Free Full Text]
- Liang EY, Cooper JE, Lam WW, Chung SC, Allen PW, Metreweli C. Case report: myolipoma or liposarcoma—a mistaken identity in the retroperitoneum. Clin Radiol 1996;51:295–297.[CrossRef][Medline]
- Wetzel LH, Levine E. MR imaging of sacral and presacral lesions. AJR Am J Roentgenol 1990;154:771–775.[Free Full Text]
Congratulations to the 23 individuals and two resident groups that submitted the most likely diagnosis (presacral myelolipoma) for Diagnosis Please, Case 135. The names and locations of the individuals and resident groups, as submitted, are as follows:
Individual Responses
- Eric L. Bressler, MD, Minnetonka, Minn
- Johannes F. De Villiers, MBChB, MMed, Gisborne, New Zealand
- Seyed A. Emamian, MD, PhD, Rockville, Md
- John W. Gianini, MD, Winston Salem, NC
- Naganathan B. Mani, MD, Miami, Fla
- Satoshi Matsushima, MD, Tokyo, Japan
- Steven J. Michel, MD, Redmond, Ore
- David M. Panicek, MD, New York, NY
- Hakmin Park, MD, Ann Arbor, Mich
- Narendrakumar P. Patel, MD, Newburgh, NY
- Ilias Primetis, MD, Athens, Greece
- Matthew C. Rheinboldt, MD, Nashville, Tenn
- Steven Schepers, Herent, Belgium
- Anthony J. Scuderi, MD, Johnstown, Pa
- Hideki Shima, MD, Tokyo, Japan
- Taro Shimono, MD, Osaka, Sayama, Japan
- Annamaria Skacelova, MD, Veazie, Me
- Annemie Snoeckx, MD, Zandhoven, Belgium
- Kouichi Sugiyama, Numazu, Japan
- Ayako Tamura, MD, Tokyo, Japan
- Eugene Tong, MD, Austin, Tex
- Ram K. Vijay, MBBS, Sheffield, United Kingdom
- Scott S. White, MD, Westborough, Mass
Resident group response
- Baylor University Medical Center Radiology Residents, Dallas, Tex
- University of Pennsylvania Radiology Residents, Philadelphia, Pa
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HISTORY
IMAGING FINDINGS
