Myelolipoma: CT and pathologic features

PURPOSE: To correlate clinical and pathologic patterns of myelolipoma with the computed tomographic (CT) appearance. MATERIALS AND METHODS: All cases of myelolipoma accessioned by the Armed Forces Institute of Pathology from 1981 through 1997 were reviewed. CT images were scored for the location and size of each myelolipoma and the presence of calcification, hemorrhage, fat, and pseudocapsule. Pathologic findings for the pattern of fat and bone marrow elements were correlated with CT findings. RESULTS: In 74 patients, 86 myelolipomas were found, of which 72 were in an adrenal gland (eight were bilateral), and 14 extra-adrenal masses were found in 10 patients. Four clinicopathologic patterns emerged: (a) isolated adrenal myelolipoma in 37 patients (fat evident at CT, no other disorders present); (b) myelolipoma with hemorrhage in nine patients (imaging features similar to those of isolated adrenal myelolipomas but larger [mean diameter, 14.2 vs 9.9 cm; P = .01]; (c) extra-adrenal myelolipomas in 10 patients (imaging findings similar to those of adrenal myelolipoma, found most often in the retroperitoneum); and (d) myelolipomatous foci within other adrenal pathologic conditions in 18 patients (smaller, lower fat content, more heavily calcified). CONCLUSION: Myelolipomas are adrenal or extra-adrenal masses, with hemorrhage more common in larger lesions (diameter, >10 cm). The CT appearance of myelolipomatous foci, which can be found within other pathologic adrenal conditions, is different from that of isolated adrenal myelolipomas.