Lipomatous hemangiopericytoma of the corpus spongiosum: a case report and review of the literature.

Background: Hemangiopericytoma (HPC) is an uncommon soft tissue tumor arising from pericytes. The urogenital system is rarely affected.

Methods: The review of the literature used the PubMed database which was searched up to March 2015.

Results: Herein, we report the first case of lipomatous HPC of the corpus spongiosum in a 37-year-old man in China. The lesion presented as a quickly growing mass. Contrast enhanced CT showed a heterogeneous fatty mass with a multifocal enhancing soft-tissue component. Microscopically, the neoplasm was composed of spindle cells, a mature fat component and collagenous stroma. The mitotic index was low at 1 to 3 mitoses per 10 high-power fields. Immunohistochemically, STAT6, Bcl-2, CD99 and CDK4 were positive; CD34 and SMA were negative. The mature adipocytes were positive for S-100. Ki-67 expression was found in approximately 5% of the tumor cells. Surprisingly, there was a diffuse and strong nuclear expression of MDM2, but, no amplification of MDM2 was demonstrated by FISH. An adequate excision of the tumor was performed.

Conclusion: No local recurrence or distant metastases occurred during the 18-month follow-up. In view of the unpredictable biological behavior of this tumor, a long follow-up period is mandatory.