Pathology: synovial chondromatosis

Multinodular; circumscribed

Clusters of polygonal-stellate cells with pale eosinophilic cytoplasm, set within lacunae

Ovoid hyperchromatic nuclei with mild atypia and occasional bi-nucleation

Abundant hyaline matrix with enchondral calcification and metaplastic bone

Multinodular; circumscribed

Clusters of polygonal-stellate cells with pale eosinophilic cytoplasm, set within lacunae

Ovoid hyperchromatic nuclei with mild atypia and occasional bi-nucleation

Abundant hyaline cartilage matrix 

RNA-Seq: FN1::ACVR2A gene fusion

Multinodular; circumscribed

Clusters of polygonal-stellate cells with pale eosinophilic cytoplasm, set within lacunae

Ovoid hyperchromatic nuclei with mild atypia and occasional bi-nucleation

Abundant hyaline cartilage matrix 

Multilobulated; circumscribed

Clusters of polygonal cells with pale eosinophilic cytoplasm, set within lacunae

Ovoid hyperchromatic nuclei with mild atypia and occasional bi-nucleation 

Abundant hyaline cartilage matrix with nodules separated by fibrous connective tissue

Multilobulated; circumscribed

Clusters of polygonal cells with pale amphophilic cytoplasm, set within lacunae

Hyperchromatic round nuclei with mild atypia and occasional bi-nucleation 

Abundant hyaline cartilage matrix

Multinodular; circumscribed

Clusters of polygonal-stellate cells with pale eosinophilic cytoplasm, set within lacunae

Ovoid hyperchromatic nuclei with mild atypia and occasional bi-nucleation 

Abundant hyaline cartilage matrix with focal enchondral calcification

Multinodular; circumscribed

Clusters of polygonal-stellate cells with pale eosinophilic cytoplasm, set within lacunae

Ovoid hyperchromatic nuclei with mild atypia and occasional bi-nucleation 

Hyaline matrix with enchondral calcification and metaplastic bone