Malignant phosphaturic mesenchymal tumor, mixed connective tissue variant of the tongue.

The majority of the oncogenic osteomalacia-associated mesenchymal tumors are considered to belong to the category of phosphaturic mesenchymal tumors, mixed connective tissue (PMTMCT) variant, of which malignant cases are very rare. Here we report a case of a recurrent malignant PMTMCT variant which arose in the tongue. The patient was treated with surgery at an initial treatment and the first recurrence. In accordance with the tumor recurrence and resection, the hypophosphatemia progressed and improved. However, hypophosphatemia did not progress after receiving radiation therapy at the second recurrence even though the recurrent tumor gradually increased its size. These results suggest clinical feature of malignant PMTMCT could be changed by radiation therapy. Thus, this report could add an insight to the nature of PMTMCT.