Phosphaturic mesenchymal
tumor (PMT) is a morphologically heterogeneous soft tissue and
bone neoplasm, producing a
paraneoplastic syndrome due to
phosphate wasting. These
tumors produce
fibroblast growth factor 23, which is implicated in renal tubule
phosphate loss. Medical records of patients seen from 1999 to 2013 with
osteomalacia associated or not with a
tumor were reviewed. Clinical and laboratory data, radiographic studies, and follow-up of 8 patients were tabulated. Histologic features and the immunoprofile of the
tumors were analyzed. There were 208 patients with
osteomalacia, but only 8 (3.84%) had
osteomalacia associated with a
tumor. The median age of the patients was 40 years. The
tumor size ranged from 1.5 to 4 cm. Five were located in soft tissues and skin; and 3, in bones.
Osteomalacia symptoms lasted from 2 to 14 years with a median of 6 years. Laboratory data showed
hypophosphatemia and
phosphaturia in all patients. All
tumors were histologically benign. Histologically, the salient features were a hemangiopericytoid pattern, chronic
hemorrhage, and microcystic areas. All
neoplasms were diffusely positive for
vimentin and focally positive for
epithelial membrane antigen, CD34, and
S-100 protein. Ki-67 was positive in approximately 10% of neoplastic cells in 2 cases and less than 1% in the remainder. We report 8 cases of
PMTs producing
osteomalacia, from a single third-level Mexican medical institution. These
tumors occurred in soft tissues, skin, and bones. All
tumors were benign, small, not easily detected by physical examination and diagnosed due to the metabolic abnormalities.