A diagnostically challenging case of phosphaturic mesenchymal tumor in an elderly woman masquerading as giant cell tumor

ABSTRACT Phosphaturic mesenchymal tumor (PMT) is a rare tumor of uncertain histogenesis composed of spindle cells in a vascularized stroma with a grungy calcified matrix and associated tumor-induced osteomalacia. Till date, <500 cases of this enigmatic tumor entity have been described. PMTs are reported in various locations, commonly involving the extremities and head-and-neck region. Often, this rare entity is under recognized by both clinicians and pathologists which is reflected by the frequent delay of diagnosis with patients suffering from disability related to their tumors for several years. Herein, we present a case of a 57-year-old female with recurrent multiple bone fractures and an abdominal wall nodule, a biopsy from which displayed sheets of osteoclastic giant cells, mimicking a giant cell tumor. Excision of the nodule was curative with normalization of biochemical parameters (serum calcium and phosphorus levels), histopathology of which was consistent with a PMT.