Conventional chondrosarcoma of the rib cage and sternum: clinicopathological and molecular analysis of 27 patients treated at a single institution.

Conventional chondrosarcoma of the chest wall is rare, accounting for 15% of cases. Our purpose was to document clinicopathological, imaging and outcome results from a novel set of chest wall chondrosarcomas, and to analyze for IDH mutations and novel molecular alterations. Gross and microscopic pathology, imaging and clinical charts were reviewed. Targeted next-generation sequencing was performed to identify somatic mutations and copy number alterations. The cohort consisted of 27 patients: 16 men and 11 women (mean age 51 years; range 23-76). Palpable mass was the most common presentation. Five were discovered incidentally. Among 20 tumors with complete imaging, 15 arose from a rib and 5 from the sternum. Seven rib tumors were central/intramedullary, 5 were periosteal, 2 were secondary peripheral chondrosarcomas, and one was indeterminate. Among sternal tumors, 4 were central/intramedullary and one was periosteal. Half the periosteal tumors arose from the costochondral junctional cartilage (CCJ). Periosteal chondrosarcomas were sometimes mistaken for extraskeletal masses on initial clinical or radiological examinations. Fifty-nine percent of all tumors were grade 1 and 41% were grade 2. None were dedifferentiated chondrosarcomas. Heterozygous IDH1 mutation was detected in one tumor and heterozygous RAD50 mutation in another. Local recurrence(s) happened in 41% and metastasis in 41%. Grade had strong association with local recurrence (25% grade 1 vs. 64% grade 2 [P = .0447]), metastatic recurrence (19% grade 1 vs. 73% grade 2 [P = .0058]), and survival. Although chest wall chondrosarcomas share morphologic and molecular features with other chondrosarcomas, there is a much higher incidence of periosteal chondrosarcomas. IDH mutant tumors are uncommon. Early diagnosis and margin-negative resection is treatment of choice since chondrosarcomas are chemo- and radioresistant.