Bronchioloalveolar carcinoma of mixed mucinous and nonmucinous type: Immunohistochemical studies and mutation analysis of the p53 gene

Bronchioloalveolar carcinoma of mixed mucinous and nonmucinous type fulfilling the 1999 WHO criteria is rare. Here, we report a case of this type of tumor determined entirely by histological examinations. A 57-year-old man was incidentally found to have a demarcated 3 cm mass in his lower lobe of the right lung. The tumor was composed of tall columnar cells containing cytoplasmic mucins, cuboidal cells without mucins, and intermediate cell types with lepidic growth patterns. Tumor cells were distributed within a region of 2 cm in diameter, and no stromal, vascular, or pleural invasion was observed. Immunohistochemically, both the mucinous and nonmucinous components were positive for cytokeratin 7, TTF-1, and E-cadherin, and negative for cytokeratin 20, consistent with the results for nonmucinous bronchioloalveolar carcinoma. No mutations were detected in exons 5–8 of the p53 gene. The present tumor was composed mainly of morphologically mucinous bronchioloalveolar carcinoma, but presented different immunohistochemical profiles of ordinary mucinous bronchioloalveolar carcinoma. This case suggests that the mucinous component in bronchioloalveolar carcinoma of mixed mucinous and nonmucinous type has characters dissimilar to conventional mucinous bronchioloalveolar carcinoma, and is probably derived from the nonmucinous component.