Intracranial phosphaturic mesenchymal tumor

Abstract

Objective One case of intracranial phosphaturic mesenchymal tumor (PMT) was reported to study the clinicopathologic characteristics, immunohistochemical features, differential diagnosis and prognosis of PMT. Methods and Results A 53⁃year⁃old man presented with 7 years history of bone pain with hypophosphatemia, aggravated for one month. A tumor was discovered in left occipital bone by ⁹⁹Tc^m-octreotide scanning. MRI showed left occipital bone and duramater masses. Tumor⁃induced osteomalacia (TIO) was diagnosed and the lesion was completely removed. The lesions meningeal tissue, periosteum and left occipital bone were examined pathologically. The microscopiy showed that the tumor growed diffusely, involving meningges and bones, and mainly composed of oval and short spindle cells. It contains malformed thick⁃walled vessels, dilated sinusoidal vessels, mature adipose tissue, interstitial mucinous degeneration and mitosis without typical mitotic activity and necrosis. Immunohistochemically, the tumor cells were positive for fibroblast growth factor⁃23 (FGF⁃23), Vimentin (Vim), somatostatin receptor 2 (SSTR2), CD56 and neuron⁃specific enolase (NSE), and focal expression of Bcl⁃2, D2⁃40; the Ki⁃67 labeling index was 5%. Pathological diagnosis was PMT. The patient's serum phosphate level returned to normal after operation. The case had followed⁃up for 22 months, and survived with normal phosphatemia and without local recurrence and distant metastasis at the last followed ⁃ up. Conclusions Intracranial PMT is very rare, and it is very difficult to detect the lesion early. The differential diagnosis should be considered with meningioma and hemangiopericytoma. Accurate localization and completely excision of tumor are effective therapeutic methods. Clinical features, blood biochemical characteristics, image localization and immunohistochemical phenotype are helpful for the correct diagnosis and identification of the spindle cell tumors such as meningoma.

DOI：10.3969/j.issn.1672⁃6731.2019.11.012