Diagnostic ultrastructural markers in alveolar cell carcinoma

Two, difficult-to-diagnose cases of metastatic alveolar cell carcinoma were examined with the electron microscope. In the first case, the prominent feature was the occurrence of intranuclear tubular inclusions and the rare occurrence of surfactant-like material between tumour cells. Only after a prolonged search in sections from several blocks were typical neoplastic type II alveolar cells with secretory granules containing myelin figures (myelinosomes) found and the diagnosis of alveolar cell carcinoma established. In the second case, the tumour cells contained single-membrane-bound bodies enclosing material resembling pulmonary surfactant. Here also, after much searching, rare cells containing myelinosomes resembling those found in type II alveolar cells were found and the diagnosis of alveolar cell carcinoma established. The value of these various markers (myelinosomes, intranuclear tubular inclusions and surfactant-like material) in establishing the diagnosis of alveolar cell carcinoma with the electron microscope are reviewed and discussed.