A CASE OF ADRENAL ADENOMATOID TUMOR DIAGNOSED BY IMMUNOHISTOCHEMICAL EVALUATION

An adenomatoid tumor is a benign tumor of mesothelial derivation, typically found in the genital track. However, though extremely rare, an adenomatoid tumor can be found in the adrenal gland, making it difficult to clinically and radiologically differentiate it from an adrenocortical tumor or a pheochromocytoma prior to surgery. We encountered a-52-year old man with an adenomatoid tumor in the adrenal gland, who presented with an incidentally discovered left adrenal mass revealed by PET-CT from his regular health examinations. He had been diagnosed with paroxysmal hypertension two years before and was being treated with a hypolipidemic agent. Abdominal computed tomography revealed a left adrenal mass measuring 25 × 15 mm, and the findings were different from the typical adrenocortical adenoma or pheochromocytoma. Although laboratory examinations of his blood samples indicated normal adrenal function, 24-hour urine specimens revealed high levels of 17-OHCS, 17-KS, and catecholamine. Both ¹³¹I-MIBG scintigraphy and phentolamine tests showed negative findings. The patient underwent a laparoscopic left adrenalectomy. The cut surface of the left adrenal gland weighing 21 g contained a white, solid mass measuring 25 × 15 × 20 mm within the adrenocortical tissue. Histologically, the tumor was composed of small tubules lined by eosinophilic tumor cells. The tumor cells were immunohistochemically positive for cytokeratins and calretinin, but negative for steroidogenic factor-1. Therefore, based on these findings, we diagnosed this tumor as an adrenal adenomatoid tumor. Histopathologically, the adrenal adenomatoid tumor may be difficult to distinguish from an adrenocortical adenoma, carcinoma, lymphangioma, hemangioma, angiosarcoma, or metastatic adenocarcinoma. Under these conditions, immunohistochemical examination is useful for definite diagnosis.