Osteoclast-like giant cell–rich carcinomas of the lung: a clinicopathological, immunohistochemical, and molecular study of 3 cases

Three cases of primary carcinomas of the lung each with an extensive osteoclast-like giant cell component are presented. The patients are 3 men between the ages of 58 and 67 years (average, 62.5 years) who presented with nonspecific symptoms. A history of malignancy, infectious, or granulomatous disease was negative in all the patients. Diagnostic imaging disclosed the presence of a large intrapulmonary mass; in 1 case in the right upper lobe and in 2 cases in the right lower lobe. Surgical resection via lobectomy was performed in the 3 patients. Grossly, the tumors were described as soft, friable intrapulmonary masses, reddish in color, and measuring from 6 to 13 cm in largest diameter. Histologically, the tumors were each characterized by the extensive presence of a multinucleated osteoclast-like giant cell component, which represented approximately 80% of the tumor mass. The osteoclast-like giant cell component was admixed with a sarcomatoid carcinoma in 2 cases and an adenocarcinoma in 1 case. Immunohistochemistry showed that the osteoclast-like giant cells were positive for CD-68, cathepsin K, and histone H3, whereas the carcinoma component was positive for keratin, thyroid transcription factor-1, and histone H3 (patchy). Molecular studies were performed in 2 patients with negative results. Clinical follow-up was obtained in 2 patients; 1 died 14 months after initial diagnosis, whereas 1 remains alive 6 months after initial diagnosis. One patient was lost to follow-up. The current neoplasms represent an unusual type of lung carcinoma that needs highlighting as a separate type from conventional giant cell carcinoma. •The extensive presence of osteoclast giant cells in non–small cell carcinomas•Separating osteoclast giant cell–rich carcinomas from conventional giant cell and pleomorphic carcinomas•Immunohistochemical stains as an aid in properly classifying these tumors