Pulmonary Pathology Online
Pathology of Basaloid Squamous Cell Carcinoma
squamous cell carcinoma of the lung, an uncommon subtype of non-small cell
carcinomas was introduced as a distinct entity in the recently revised
World Health Organization (WHO) classification of lung tumours.
The histopathologic features distinguishing this tumour from other non-small cell lung cancers are a lobular growth pattern of small cells with moderately hyperchromatic nuclei, with no prominent nucleoli, and with scant cytoplasm, a high mitotic rate, and peripheral palisading.
Basaloid carcinoma may be present in a pure form and the others may be of a mixed, but prominent, basaloid type associated with squamous cell carcinoma, large cell carcinoma, or adenocarcinoma.
Immunohistochemical studies in a case of necropsy specimen indicated that the tumour was positive for keratin, vimentin, and S100, and negative for chromogranin A, cytokeratin CAM5.2, and bcl-2.
Ultrastructural study showed an absence of neurosecretory granules and the presence of some squamous and/or glandular differentiation.
This morphologic and immunologic phenotype suggests that basaloid carcinoma is derived from a pluripotent reserve cell or a basal bronchial epithelial stem cell.
Differential diagnosis include small cell carcinoma, neuroendocrine large cell, adenoid cystic carcinoma and poorly differentiated squamous cell carcinoma.
Basaloid carcinoma of the lung is a highly aggressive form of nonsmall cell lung cancers.
Even in stage I and II of basaloid carcinoma, a 5-year survival rate of only 15% has been reported.
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