Primary clear cell adenocarcinoma of the lung.

Primary clear cell adenocarcinoma of the lung is extremely rare. A 63-year-old Japanese man consulted to our hospital because of cough and sputum. Imaging modalities including XP, CT and MRI revealed a tumor of the right middle lobe. They did not identify other tumors in the body. Because clinical cytology and biopsy showed malignant cells, segmentectomy of the lobe was performed. Grossly, the tumor was whitish tan tumor measuring 5 × 6 × 5 cm. Histologically, the tumor was composed entirely of clear cells arranged in papillary and tubular patterns. The tumor cells had hyperchromatic nuclei, and mitotic figure and nuclear stratification were scattered. Histochemically, glycogen and mucins were absent in tumor cell cytoplasm. Immunohistochemically, the tumor cells were positive for pancytokeratin (AE1/3, CAM5.2), cytokeratin (CK) 7, CK 8, CK18, CK19, EMA, CEA, CA19-9, CA125, p53, Ki-67 (labeling = 80%), TTF-1 and surfactant apoprotein A. In contrast, the tumor cells were negative for CK5/6, CK 34βE12, CK 14, CK 20, vimentin, desmin, S100 protein, α-smooth muscle actin, AFP, HMB45, CD10, CD34, HER2/neu, CD56, p63, and synaptophysin. The tumor recurred 6 months after the operation, and right middle lobectomy was performed. Postoperative imaging modalities showed no tumors. The patient is alive free from tumor 9 years after the first manifestation.