Osteosarcoma in Paget Disease of Bone

Comments:
Paget Sarcoma - Microscopic: The most common subtype is osteosarcoma (80% of cases) which may be osteoblastic or fibroblastic. Other neoplasms include fibrosarcoma, chondrosarcoma, undifferentiated pleomorphic sarcoma (MFH) and even giant cell tumor (GCT).

Severe Paget disease of bone (PDB) associated with GCT has been linked to a missense mutation in ZNF687 which encodes zinc finger protein 687. Like SQSTM1/p62 protein, 687 also plays a role in NF-κB signaling. For unexplained reasons, the association of GCT with PDB is more frequently seen in the Campania region of Italy.

About this image: Fibroblastic osteosarcoma (right two-thirds) arising in the setting of PDB (left one-third). The pagetic bone shows increased osteoclastic activity with resorption pits, large osteoclasts with numerous nuclei, and thick plate-like bony trabeculae with numerous, irregular blue cement lines, creating a mosaic pattern.