Primary mixed squamous carcinoma and osteosarcoma (carcinosarcomas) of the lung have a CGH mapping similar to primitive squamous carcinomas and osteosarcomas.

Carcinosarcomas are malignant tumors with a mixture of carcinomatous and differentiated sarcomatous elements. We investigate the morphology, immunohistochemistry, and comparative genomic hybridization analysis of 3 mixed squamous carcinoma and osteosarcoma of the lung. All patients were male and their ages were 72, 43, and 58 years. The sizes of the neoplasms were 7, 5, and 5 cm in maximum diameter, respectively. Two patients died of the disease 9 and 14 months after surgery; and one is alive 6 months later. By light microscopy, all cases had both squamous and osteosarcomatous structures. Immunohistochemistry was positive for AE3AE1, p63, 34 E12, CAM 5.2 (2/3 cases), CK-7 (2/3 cases), epithelial membrane antigen, E-cadherin, p53, and carcinogenic embryonic antigen in carcinomatous areas, and for vimentin and CD-68 in sarcomatous component. Areas of transition positive for both cytokeratins and vimentin were seen in all cases. A total of 55 copy number changes were detected with a median of 18 abnormalities per case: 48 gains, 6 losses, and 1 high-level amplification. Chromosome alterations in osteosarcomatous areas were similar to those found in lung metastatic osteosarcoma, comparable to those found in carcinomatous areas and to lung squamous carcinomas. Coincidences between carcinomatous areas and osteosarcomatous zones were found as gains in chromosomes 1q, 3q, 5p, 8q, and 12p. These findings provide arguments that favor a common origin for both types of cells, supported by the mixture of cells, the existence of undifferentiated cells positive to both cytokeratin and vimentin markers, and the CGH overlaps of chromosomal gains between carcinomatous and sarcomatous areas.