Large-cell lung carcinoma with basaloid architecture and neuroendocrine differentiation: a new type of combined large-cell neuroendocrine carcinoma.

One of the main differential diagnostic issues in pulmonary large-cell carcinomas is that involving neuroendocrine (NE) and basaloid histotypes. The differential diagnosis of basaloid versus large-cell NE carcinoma requires immunohistochemical determination of NE markers because of morphological overlap between the 2 entities. The authors report a unique case of lung carcinoma with basaloid architecture and NE immunohistochemical features observed in a 64-year-old male smoker who underwent upper left lobectomy for a neoplastic stenosis of the lobar bronchus. The patient died 14 months after surgery. Histological examination showed multiple peripheral nodules of moderately enlarged neoplastic cells with irregular nuclei, with granular chromatin and frequent nucleoli, and diffuse in situ neoplasia involving bronchi, peribronchial glands, and small airways. Immunohistochemistry documented diffuse expression of CD56 in neoplastic cells and isolated cell groups immunoreactive for basal cell markers. The reported case was considered an as-yet-undescribed tumor showing both basaloid and NE differentiation.