# Osteolytic mystery: A rare case of pathologic fracture from a phosphaturic mesenchymal tumor in hip and femur

## TL;DR

A rare tumor in the hip and femur caused bone damage and was initially mistaken for multiple myeloma.

## Contribution

This case highlights the diagnostic challenges and management of a rare phosphaturic mesenchymal tumor.

## Key findings

- PMT was misdiagnosed as multiple myeloma due to similar symptoms and imaging features.
- Biopsy confirmed the presence of PMT with characteristic histological features.
- Surgical intervention and follow-up imaging were necessary for treatment.

## Abstract

Phosphaturic mesenchymal tumor (PMT) is a rare tumor causing bone complications and myopathy. Histologically, PMT displays a mix of spindled cells, osteoclast-like giant cells, basophilic matrix, and flocculent or “grungy” calcification. Here we describe a case of PMT in the right hip and proximal femur, initially suspected to be multiple myeloma, presenting with osteolytic lesions and elevated alkaline phosphatase. Tests for malignancy were negative, but a subsequent biopsy confirmed PMT. The patient underwent hip biopsy, femur resection, and hemiarthroplasty, with follow-up MRI recommended.