Basaloid squamous carcinoma of the oesophagus: a distinct neoplasm with multipotential differentiation

Basaloid squamous carcinoma (BSC) is an uncommon variant of squamous cell carcinoma, with its prevalent sites being the hypopharynx, tongue base and larynx. In the oesophagus, BSC is rarer than in the head and neck region. This study was aimed to document the clinicopathological features of BSCs of the oesophagus, and to present their relative incidence and immunohistochemical findings.

Eighteen cases of BSC of the oesophagus, comprising 3.6% of 502 oesophageal carcinomas, were reviewed for their pathological and clinical features, and examined for the immunohistochemical expression of neuroendocrine markers, cytokeratins, p53, pRb and bcl-2. Oesophageal basaloid squamous carcinomas tended to be biphasic or multiphasic carcinomas, most commonly with basaloid and squamous components (eight cases), or with additional adenocarcinoma (three cases) or with small cell carcinoma (two cases). Each component was microscopically clearly distinguishable from the others, and metastasized separately, chiefly the basaloid component. The remaining five cases were apparently pure basaloid carcinomas, being characterized by lobules and nests of monotonous round undifferentiated cells with frequent comedo necrosis. They resembled, but were differentiated from, the small cell carcinoma on the basis of neuroendocrine markers and cytokeratin expression. p53, pRb and bcl-2 oncoprotein, which are known to normally present in the basal/parabasal cells of the oesophageal epithelium, were detected in 40-50% of cases, with a heterogeneous expression pattern. The patients were all male, with the age ranging 47-74 years (median 57) and presented at variable stages. The plotted 3 years survival rate was 51%, and the immunohistochemical expression of p53, pRb and bcl-2 was not related to the survival of the patients.

Basaloid squamous carcinoma of the oesophagus is a peculiar neoplasm with a capacity of multidirectional differentiation, often with heterogeneous oncogene expression, probably reflecting the pluripotential stem cell origin.