Calcified chondroid mesenchymal neoplasm: a clinicopathological and molecular analysis.

Aims: Calcified chondroid mesenchymal neoplasm (CCMN) is a recently identified category of soft tissue neoplasms defined by cartilage or cartilaginous matrix formation and FN1 gene fusions. Its rarity and similarities to other soft tissue tumours pose diagnostic challenges. This study aims to deepen understanding of CCMN, highlighting molecular pathology's role in diagnosis to reduce misdiagnosis, overdiagnosis and overtreatment.

Methods: We conducted a clinicopathological analysis of five newly identified CCMN cases and reviewed 87 cases documented in PubMed. Next-generation sequencing was used to detect molecular alterations, while clinical, radiological and histopathological features were extensively reviewed.

Results: CCMN typically affects adults, presenting as a slow-growing, painless mass in soft tissue. Histologically, CCMN exhibits a chondroid matrix with variable calcification. Molecular analyses in our cases identified FN1::FGFR1, FN1::FGFR2 and FN1::TEK fusions. Review of the 87 cases revealed consistent clinical, imaging and molecular profiles, underscoring CCMN's distinct characteristics.

Conclusions: CCMN should be considered in the differential diagnosis of soft tissue tumours with chondroid and calcified components. Detecting FN1 gene fusions aids in distinguishing CCMN from morphologically similar tumours.