Unexpected diagnosis of multiple sclerosing pneumocytomas in a patient with chondrosarcoma of the hand.

Sclerosing pneumocytomas are rare, benign pulmonary neoplasms that predominantly affect Asian female patients in the age category of 40-70 years, mostly non-smokers. We report on a 72-year-old Caucasian woman with chondrosarcoma of the hand who developed multiple bilateral progressive lung nodules suspicious of lung metastases. Staged lung resections were performed, and pathological diagnosis was confirmed by immunohistochemical analysis of the resected specimens. Next-generation sequencing (NGS) was used to detect gene mutations. Immunohistochemistry demonstrated sclerosing pneumocytomas, and NGS showed an IDH1 mutation. Eventually, the patient developed lung metastases for which rethoracotomy was performed. The differentiation of sclerosing pneumocytoma from lung cancer is a diagnostic challenge, and sclerosing pneumocytoma should be considered in the differential diagnosis of pulmonary nodules. Gene mutation analysis does not always show classical and common mutations, which should be kept in mind when interpreting its results.