MIXED SMALL-CELL LARGE-CELL CARCINOMA OF THE LUNG - REPORT OF A CASE WITH CYTOLOGIC FEATURES AND ULTRASTRUCTURAL CORRELATION

BACKGROUND: Mixed small cell/large cell carcinoma of the lung, a cheme therapy- and radiation-resistant subtype of small cell lung cancer, co nstitutes 4-6% of small cell lung cancer but has been described rarely in the cytopathology literature. CASE: A 64-year-old man presented wi th a left hilar mass. A concurrent transbronchial biopsy and postbiops y bronchial washing were performed. The latter presented as loosely co hesive cells, scattered singly, in small clusters, in monolayer sheets and in a perivascular arrangement. The tumor exhibited a wide spectru m of cytomorphology: small cells with pyknotic nuclei and scanty cytop lasm were admixed with larger cells with vesicular nuclei, prominent n ucleoli and abundant cytoplasm. Nuclear shape included oval, spindle a nd peg. Nuclear size was also highly variable. The tumor was retrieved from the transbronchial biopsy and processed for ultrastructural stud y. CONCLUSION: Based on cytologic-ultrastructural correlations, the se emingly ''mixed'' morphology may have resulted from the rapid degenera tion of a single clone of tumor cells: the viable tumor cells were the ''large'' cells, and the dying cells were the ''small'' cells. A nove l ultrastructural observation is that the perivascular tumor cells dev eloped peculiar, fingerlike cytoplasmic processes abutting an undulati ng basement membrane along the thin-walled blood vessel.