Re: Giant lipoma of the adrenal gland.

Abstract

To the Editor. The authors report a case of giant lipoma of the right adrenal gland, which was found incidentally during ultrasonographic examination following a car accident. Lipoma is composed of mature adipose tissue, and occasionally has fibrous connective tissue as septations.1 Therefore, lipoma appears on computerized tomography as a well defined homogeneous tumor with low attenuation value. However, in figure 1 in the article the right adrenal tumor demonstrates a large amount of nonfatty soft tissue attenuation material. This finding suggests adrenal myelolipoma rather than pure lipoma since the nonfatty soft tissue in the reported tumor may represent hematopoietic cells. Adrenal myelolipoma is more common than lipoma, and is composed of hematopoietic cells and fat similar to bone marrow. Myelolipoma typically manifests as a well defined suprarenal mass with an area of clearly recognizable fat attenuation. Some higher attenuation areas are usually seen, often with attenuation readings less than that of true soft tissue, as well as indistinct margins because of the irregular intermixture of fat and myeloid elements seen microscopically.2, 3 On magnetic resonance imaging predominantly fatty areas usually have increased signal intensity on T1-weighted images and moderate hyperintensity complicated by the presence of marrow-like elements in the corresponding regions on T2-weighted images.3 Calcification is rare in pure lipoma but has been observed in 24% of reported cases of myelolipoma.2, 3 To make a diagnosis of pure lipoma, there should not be any evidence of hematopoiesis or adrenal medulla cells on serial sections. If a pathologist examines only the fatty component of myelolipoma, the tumor can be misdiagnosed as lipoma. In previously reported cases of adrenal lipoma there was no pathological evidence of hematopoietic elements despite the fact that serial sections or multiple blocks were taken from the lesions.4–6 Another possibility is that the nonfatty material in the tumor may represent intratumoral bleeding due to trauma. However, this possibility is less likely in this case because there is no evidence of rib fracture or abdominal wall injury in figure 1. Myelolipomas with hemorrhage have been reported in larger lesions, and the appearance of the myelolipoma is altered on imaging.2, 3 Angiomyolipoma, liposarcoma and teratoma may also be included in the differential diagnosis based on computerized tomography findings but these tumors are extremely rare at the adrenal gland.1 We recommend that the authors conduct a careful pathological examination of serial sections, and hope that they will report the composition of the nonfatty material in the tumor.