Ultrastructural findings in metastatic bronchioloalveolar carcinoma.

This study was prompted by the recent revision of the definition of bronchioloalveolar carcinoma (BAC) that defines BAC, light microscopically, as a non-invasive carcinoma. Doubt has been raised whether BACs retain certain specific microscopic features after becoming invasive or metastatic. We studied 7 cases of metastatic, non-mucinous BAC by electron microscopy. Of these cases, 5 showed Clara cell granules and 1 revealed lamellar bodies. The remaining case did not show ultrastructural features of BAC. These findings suggest that most BACs retain some of their ultrastructural features after becoming metastatic neoplasms.