Clinicopathological study of 47 cases of sebaceoma.

BACKGROUND: Sebaceoma is a rare and poorly understood form of sebaceous tumour, and it is of great significance since it may reveal Muir-Torre syndrome (MTS). Herein, we present a series of cases with details of the histopathological appearance.

PATIENTS AND METHODS: We examined records of cases labelled as sebaceous tumour recorded at the Strasbourg Dermatopathology Laboratory between 1991 and 2015. We include cases of benign sebaceous tumour predominantly involving immature basophilic cells. The clinical and histological data were collected as well as screening for a history of MTS.

RESULTS: We studied 47 cases of sebaceomas (26 men), in patients of mean age 67.6years, located primarily in the head or neck (32 cases). Of the 17 patients followed up, 6 had MTS. Different types of architecture were seen: dermal nodule (9 cases) or cystic nodule (9 cases), multiple dermal nodules (22 cases), exophytic tumour (4 cases) and an appearance intermediate with sebaceous adenoma (3 cases). The cells involved were basophilic, with the presence of round ducts exhibiting an eosinophilic cuticle and, in rare cases, mature sebocytes. Mitoses were observed: mean 6.6/10 fields (0 to 19). In all cases, there was expression of CK17, EMA and androgen receptors, but not of BerEP4.

DISCUSSION: Sebaceoma is a small benign tumour but identification is imperative due to association with MTS. A knowledge of the associated cytological and architectural elements - particularly cysts and labyrinthine patterns - and immunolabelling enable differential diagnosis with respect to other tumours. The extra-facial and cystic forms in particular require screening for MTS. If there is any doubt, immunolabelling of androgen receptors provides a precious tool.