A paucicellular lesion with a lobulated architecture is typical. The lobules are not especially prominent here, so use your imagination.
Stellate cells with long delicate processes (that seem to interconnet) are embedded in an abundant myxoid matrix.
Chondromyxoma fibroma is an uncommon benign intramedullary tumor.
The overall picture is that of a paucicellular lesion arranged in a lobular pattern. There is a nodular/lobular proliferation stellate cells within a myxoid loosely-textured stroma. There is more pronounced cellularity at the periphery of the lobules. The stellate cells have long delicate processes that seem to interconnect. Occasionally, enlarged hyperchromatic and slightly atypical stellate cells are present, but these are not malignant. Necrosis and mitotic activity are not seen.
The differential diagnostic considerations include chondroblastoma (lacks lobular growth with peripheral increase in cellularity, and is exclusively centered in the epiphyses), enchondroma (contains true cartilege with round and not stellate cells), chondroblastic osteosarcoma (focal hyaline carilege, dense growth associated with osteoid, atypical spindle cells) and chondrosarcoma (aggressive radiographic appearance, center of lobules are hypercellular, and lobule formation is note quite as distinct)(Folpe, Fletcher).
Typically occurs in young adults. Pain is usually mild and of long duration. It most commonly arises in the proximal tibia or distal femur. Other sites include the small bones of the feet.
Imaging shows a lytic lesion with well-circumscribed lytic lesion with a scalloped and sclerotic border (Folpe, Fletcher).Swelling and tenderness most often accompanies lesions in the small bones of the extremities.
Benign; excision in curative although recurrence can be as high as 20% (Fletcher).
→Lobules of myxoid stroma containing stellate cells are characteristic features of this tumor.
→The lobules are more cellular in the periphery.
Fletcher CDM, ed. Diagnostic Histopathology of Tumors. 3rd Ed. Philadelphia, PA: Elsevier; 2007: 1607.
Folpe AL, Inwards CY. Bone and Soft Tissue Pathology: Foundations in Diagnostic Pathology Philadelphia, PA: Elsevier; 2010: 337-9.