Oncocytic adrenocortical
neoplasm is characterized by abundant eosinophilic cytoplasm containing mitochondria, occasional nuclear atypia and diffuse growth pattern. Oncocytic adrenocortical
neoplasm arising in adrenal rest is, however, extremely rare. We report a case of oncocytic adrenocortical
neoplasm arising in adrenal rest of the broad ligament with associated marked lipomatous
metaplasia. A well circumscribed
tumor was accidentally detected in the pelvic cavity of a 29 year old Japanese woman, adjacent to the broad ligament of the uterus. The
tumor was composed of large eosinophilic cells associated with diffuse growth pattern and abundant mature adipose tissue admixed with foci of clear cells. Both steroidgenic factor 1 (SF-1) and
alpha-inhibin were immunohistochemically positive in
tumor cells. Abundant mitochondria detected by immunohistochemical and electron microscopic examination confirmed the diagnosis of oncocytic adrenocortical
neoplasm. The absence of
necrosis, capsular and vascular invasion as well as the low mitotic index indicated the benign potential of this
tumor. The
tumor cells were also positive for dehydroepiandrosteron-
sulfotransferase (
DHEA-ST), 17β-hydroxysteroid
dehydrogenase type 5 (17β-HSD5), 3β-hydroxysteroid
dehydrogenase (3β-HSD) and
steroid 17α-hydroxylase (P450-c17), suggesting a possible production of
testosterone of this
tumor. This is the first reported case of oncocytic
adrenocortical adenoma arising in adrenal rest of the broad ligament.