An unusual cribriform variant of salivary basal cell tumours: a clinicopathological study of 22 cases

Abstract

AIMS: To clarify the clinicopathological characteristics of salivary basal cell tumours exhibiting cribriform architecture, and to discuss the differential diagnosis of these tumours with regard to adenoid cystic carcinoma (AdCC). METHODS AND RESULTS: Eighteen basal cell adenomas (BCAs) and four basal cell adenocarcinomas (BcACs) with at least a 10% area of cribriform morphology were collected, and the histological and immunohistochemical features were evaluated. The majority of tumours showed the typical histological patterns of basal cell tumours, in addition to cribriform architecture. In some areas, the periphery of cribriform nests had a palisade arrangement. Focal capsular infiltration, but not invasion of surrounding normal tissue, was detected in 14 of 18 BCAs. The capsules were absent or incomplete and mainly accompanied by focal invasion in BcACs. Cystic degeneration was observed in 12 of 22 tumours. The Ki67 labelling index of basal cell tumours was significantly lower than that of cribriform AdCCs (P = 0.001). All patients had a good outcome after a follow-up of 15-96 months. CONCLUSIONS: The cribriform variant shares most of the clinicopathological features of conventional basal cell tumours. Admixtures of cribriform and trabecular or tubulo-trabecular subtypes, peripheral palisading, cystic changes, non-invasive or low-grade invasive growth patterns and a low Ki67 labelling index may be useful for distinguishing basal cell tumours with a cribriform architecture from AdCCs.