This mass was resected from a patient with bone pain. What is your diagnosis?
Answer: Phosphaturic mesenchymal tumor associated with osteomalacia. This type of tumor contains areas of “grungy” mineralization, small cells, and often has a hemangiopericytomatous vascular pattern. It is often but not invariably associated with oncogenic osteomalacia. Dr. Andrew Folpe has written many interesting articles on these tumors.
Folpe AL. Phosphaturic mesenchymal tumors: A review and update. Semin Diagn Pathol. 2019;36(4):260-268.