Intraventricular solitary fibrous tumor

Abstract

Background Solitary fibrous tumor (SFT) is a mesenchymal neoplasm of specialized fibroblastic lineage, which frequently occurs in the subcutaneous and deep soft tissue of pleura,mediastinum, head and neck, extremities and trunk. Although most SFTs of the central nervous system (CNS) are dural based, a small subset presents as intraventricular without dural connection. It is a diagnostic challenge for radiologists and histopathologists to differentiate intraventricular SFT from other lesions, such as intraventricular meningioma, synovial sarcoma and Schwannoma, because of the similarities in radiological and histological findings. Herein we describe one case of unusual intraventricular primary SFT in right lateral ventricle. The radiology and clinicopathology of this lesion, as well as its differential diagnosis are discussed. Methods The clinical data of one patient with intraventricular SFT occurring in right lateral ventricle was presented retrospectively. Gross totally resected mass was routinely paraffin embedded and stained with hematoxylin and eosin. Dako EnVision immunohistochemical staining system was used to detect antigen expressions, including vimentin (Vim), cytokeratin(CK), CD34, CD99, Bcl-2, epithelial membrane antigen (EMA), glial fibrillary acidic protein (GFAP), S-100 protein (S-100), smooth muscle actin (SMA) and desmin (Des). Results A 50-year-old man presented with progressively aggravated headache for over 2 months. CT revealed a slightly high-density mass in trigone of right lateral ventricle. MRI showed an intraventricular mass with isointense signal on T₁WI, and mixed hyperintensity and hypointensity signal with "black and white pattern" on T₂WI. The mass revealed heterogeneous enhancement after gadolinium administration. Preoperative magnetic resonance angiography (MRA) displayed a highly vascularized lesion with late and persistent enhancement. During surgery, the mass was grey-red, had no capsule and connected with choroid plexus, with moderate texture and rich blood supply. It was located in lateral ventricle entirely. The tumor was removed totally. Microscopic examination showed that the mass was composed of spindle cells, dense collagenous matrix, and prominent blood vessels. In some areas, the hypocellular and alternating hypercellular arrangement, and perivascular hyalinization were found. The tumor was lack of any specific arrangement, resulting in a "patternless pattern". The myxoid matrix was observed in some areas of tumor. However, in other areas, the tumor was composed of markedly spindle cells with branching or "staghorn" vessels, resembling hemangiopericytoma. The spindle tumor cells showed mild atypia without active mitoses and necrosis. Immunohistochemically, the tumor cells were diffusely positive for Vim, CD34 and Bcl-2, focally positive for CD99, and were negative for CK, EMA, GFAP and S-100, SMA and Des. Reticular fiber staining revealed rich reticular fibers within the tumor tissue, and a pericellular pattern was also seen. Fluorescence in situ hybridization (FISH) assay for SYT rearrangement showed there was absence of t (X; 18) (p11; q11) in the tumor cells. Based on clinical presentation and histological findings, a final diagnosis of intraventricular primary SFT in right lateral ventricle was made according to the criteria of WHO classification. The patient did not received radiotherapy and was followed-up for one year, without any neurological deficit or signs of recurrence. Conclusions Intraventricular SFT is extremely rare and a definite diagnosis should be made under microscopic examination because the preoperatively radiological appearance does not differ from other tumors occurring in ventricle. Since a spectrum between SFT and hemangiopericytoma has been suggested because of overlapped morphological and immunohistochemical features, a diagnostic term of "SFT/ hemangiopericytoma" is suggested for those lesions occurring in CNS. Due to the rarity of its site, strictly differential diagnosis should be made when an isolated SFT is encountered in ventricles.

DOI: 10.3969/j.issn.1672-6731.2015.10.010