Mucinous and nonmucinous bronchioloalveolar adenocarcinomas have distinct staining patterns with thyroid transcription factor and cytokeratin 20 antibodies

We studied 14 mucinous and 26 nonmucinous bronchioloalveolar adenocarcinoma s (BACs) with thyroid transcription factor (TTF), cytokeratin (CK) 7, CK20, and villin to characterize their staining patterns with these antibodies a nd identify staining differences between the neoplasms. We also stained 11 mucinous colon adenocarcinomas with the same antibodies to compare their re action patterns with mucinous BACs. All pulmonary neoplasms were confirmed pulmonary primary BACs. Three (21%) of 14 mucinous neoplasms had weak TTF r eactivity in fewer than 25% of neoplastic cell nuclei, and the other 11 (79 %) were nonreactive. In contrast, 24 (92%) of 26 nonmucinous BACs were stro ngly TTF reactive. Eleven mucinous BACs (79%) had CK20 reactivity in more t han 25% of neoplastic cells, whereas only 1 nonmucinous BAC (4%) had reacti vity in fewer than 50% of the cells. One mucinous BAC (7%) had villin react ivity in approximately 10% of the neoplastic cells. All mucinous colon aden ocarcinomas were diffusely reactive with CK20 anti villin. Mucinous and non mucinous BACs have disparate staining patterns with TTF and CK20. Mucinous BACs are usually TTF nonreactive and CK20 reactive, but nonreactive with vi llin, which distinguishes them from mucinous colon adenocarcinomas.