A Rare Entity of an Unusual Site: Adenomatoid Tumour of the Adrenal Gland: A Case Report and Review of the Literature

This is a case report of a 51 year old male who was found to have an incidental left sided non-functioning adrenal mass on routine medical examination and which was confirmed by CT and MRI scans. A laparoscopic left adrenalectomy was done. On gross examination the tumour was a solitary well circumscribed solid-cystic mass with a homogenous pinkish white cut surface. On microscopic examination, the tumour was composed of variably sized tubules and fenestrated channels lined by bland cuboidal cells to epithelioid cells. There was focal extension to capsule and peri-adrenal fat. Immunohistochemically the tumour cells stained with calretinin, Cam5.2, CK7, vimentin and focally with EMA. Ki-67 fraction was <1%. They were negative for ER, CD31, CD34, Factor 8, chromogranin, synaptophysin S100 and inhibin. A diagnosis of an adenomatoid tumour as made. Adenomatoid tumours are rare benign tumours of mesothelial derivation. The adrenal gland is devoid of a mesothelial lining and the most accepted hypothesis for an adenomatoid tumour originating in the adrenal gland is derivation from mesothelial rests. As the adrenal gland is an extremely rare site of occurrence for an adenomatoid tumour, it is frequently mistaken for adrenocortical tumours or a pheochromocytoma clinically and radiologically. 1. Introduction Adenomatoid tumours are rare benign tumours of the mesothelial origin. The tumour may pose a diagnostic challenge if encountered at unexpected sites, which are devoid of a mesothelial layer. Here we report a case of an adenomatoid tumour of the adrenal gland, clinically suspicious for a malignant tumour. A 51-year-old male was found to have an incidental left-sided nonfunctioning adrenal mass on routine medical examination. CT and MRI scans revealed solid well-defined left adrenal tumour. Excision was recommended to confirm the nature of the mass, subsequent to which a laparoscopic left adrenalectomy was done. On gross examination the tumour was a solitary well-circumscribed solid-cystic mass with a homogenous pinkish white cut surface (Figure 1). On microscopic examination, the tumour was composed of variably sized tubules and fenestrated channels lined by bland cuboidal cells to epithelioid cells (Figures 2(a) and 2(b)). The tubules surrounded the adrenal cortical tissue, imparting a false infiltrative pattern. Adrenal medulla was barely recognizable. Focal extension to capsule and periadrenal fat was present. Aggregates of mature lymphocytes were seen with foci of calcification. No mitosis, cytological atypia, or nuclear pleomorphism was seen.