Combined plasmacytoma and squamous cell carcinoma.

A 63-year-old man was admitted to the Cardiothoracic Department of Glasgow Royal Infirmary for surgical treatment of a left suprahilar opacity. A left pneumonectomy was required to deal with an extensive upper lobe tumor. Histopathological examination, in addition to a moderately well-differentiated squamous cell carcinoma, revealed the presence of a band-like infiltrate of plasma cells and lymphoplasmacytoid cells at the main bronchial resection margin. Immunohistochemical studies confirmed this to be an extramedullary plasmacytoma by showing IgA and kappa positive monotypic cells. No paraprotein was detected in the serum. The value of immunohistochemistry in the differential diagnosis has been emphasized.