Pulmonary adenocarcinoma with micropapillary component: an immunohistochemical study. Case report.

Micropapillary carcinoma has been described in various organs, including the breast, urinary bladder, ovary and lung. We here present a case of pulmonary micropapillary carcinoma in a 72-year-old Japanese man who died of respiratory failure and septic shock, following which autopsy was performed. A mass measuring 2.5 x 2.5 x 2.5 cm was observed in the left lower lobe of the lung. The tumor showed moderately differentiated papillary adenocarcinoma with a focal micropapillary component. Carcinomatous lymphangiosis was also observed in the left lung and metastatic lesions were observed in the bilateral lung, liver, vertebra, muscle layer of the urinary bladder, right adrenal gland, spleen and lymph nodes. The micropapillary component was predominant at some metastatic sites. Immunohistochemically, both the adenocarcinoma and micropapillary components were positive for cytokeratin (CK) 7, CK19, TTF (thyroid transcription factor)-1, carcinoembryonic antigen (CEA) and surfactant apoprotein A (SP-A), and negative for CK20, estrogen receptor, progesterone receptor, uroplakin III, and CA125. The invasive area of the conventional adenocarcinoma component contained a large number of myofibroblasts, whereas the stroma of the micropapillary component contained a small number of myofibroblasts. However, no myofibroblasts were observed in the stroma of the central core of the non-invasive micropapillary carcinoma. Several lymphatic invasions by neoplastic cells were identified in the peripheral area of the micropapillary component using D2-40 antibody. The immunohistochemical profile may be helpful in determining the primary location of the neoplasm containing micropapillary features. Myofibroblasts are present in the stroma of the invasive neoplastic nests in the micropapillary component as well as the conventional adenocarcinoma component, and D2-40 monoclonal antibody may be useful for evaluating the lymphatic invasion of pulmonary micropapillary carcinoma.