Intracranial Primary Malignant Solitary Fibrous Tumor/Hemangiopericytoma Masquerading as Meningioma: Report of a Rare Case

Abstract

Background: Intracranial solitary fibrous tumors/hemangiopericytomas (SFTs/HPCs) are rare spindle cell tumors originating from interstitial tissue that are usually benign. Primary malignant intracranial SFTs/HPCs are extremely rare. Here we describe a case of malignant intracranial SFT/HPC.

Case presentation: A 59-year-old woman presented with a space-occupying lesion in the left cerebellar tentorium. Based on imaging findings, we made a preoperative diagnosis of meningioma. During the operation, we found that the tumor had an abnormally rich blood supply and could not be completely removed. Histologic findings, immunophenotype (positive for cluster of differentiation [CD]34, CD99, signal transducer and activator of transcription 6, and B cell lymphoma 2), and a Ki-67 proliferative index of 20-30% for the primary tumor were typical of malignant intracranial SFT/HPC. The tumors showed high sensitivity to radiotherapy and the residual tumor was significantly reduced after intensity-modulated radiation therapy. The patient has had no neurologic symptoms and no recurrence of the tumor in 2 years of follow-up.

Conclusion: Intracranial SFTs/HPCs are extremely rare. Radiologic examination before the operation is helpful for making a definite diagnosis and judging tumor grade; STAT6 immunohistochemistry is a sensitive alternative diagnostic method. Adjuvant radiotherapy is effective in cases of incomplete resection, and strict follow-up is essential in order to monitor for possible recurrence.

Keywords: intracranial; malignant; radiation therapy; solitary fibrous tumor.

Figure 1

MRI of the patient with intracranial SFT/HPC. (A) MRI scan revealing tumors uneven enhancement, with large zones of edema around the tumors. (B and C) Postoperative residual tumor (B) with a significantly reduced signal after 2 months of radiotherapy (C).

Figure 2

Hematoxylin and eosin staining of the SFT/HPC specimen. (A) An abundance of blood vessels was observed in tumor tissue, with an typical “staghorn” vascularization and a large number of fusiform tumor cells arranged in bundles between blood vessels. Magnification: 100×; scale bar: 100 μm. (B) Mitotic bodies were clearly visible (black arrow; ≥5 mitoses per 10 high-power fields). Magnification: 400×; scale bar: 100 μm.

Figure 3

Immunohistochemical analysis of the SFT/HPC specimen. (A–C) with immunopositivity for CD34 (A), STAT6 (B), and BCL-2 (C). Magnification: 400×; scale bar: 100 μm.