Non-small cell lung carcinoma with clear cell features: a clinicopathologic, immunohistochemical, and molecular study of 31 cases.

Non-small cell lung carcinoma with predominantly clear cell features is a rare histologic presentation of lung carcinoma. We have examined 31 cases of lung carcinomas showing extensive clear cell features. The patients were 10 women and 21 men aged 47-92 years (mean: 70 years). The tumors showed a predilection for the right upper and lower lobes and measured from 0.8 to 9.5 cm (mean: 4.2 cm). By immunohistochemistry, 9 cases were typed as adenocarcinoma, 19 cases as squamous cell carcinoma, and 3 showed a "null" phenotype with complete loss of markers for adenocarcinoma or squamous cell carcinoma. Most cases that typed as adenocarcinoma showed a solid growth pattern. A subset of the solid adenocarcinoma cases showed a distinctive "pseudosquamous" morphology. Next-generation sequencing was performed in 20 cases and showed a variety of molecular alterations. The most common abnormalities were found in the TP53 gene (9 cases), FGFR gene family (8 cases), KRAS (5 cases), AKT1 (5 cases), and BRAF (3 cases). Clinical follow-up was available in 21 patients; 16/21 patients died of their tumors from 6 months to 12 years after initial diagnosis (mean: 4.2 years, median: 1.5 years). Four patients were alive and well from 4 to 27 years (mean: 11.5 years, median: 7.5 years); all were pathologic stage 1 or 2. NSCLC with clear cell features can display aggressive behavior and needs to be distinguished from various other tumors of the lung that can show clear cell morphology. The identification of targetable molecular alterations in some of these tumors may be of value for therapeutic management.