Giant cell-rich solitary fibrous tumour of the urinary bladder: case report of an unusual histological variant and literature review

Abstract

Background: Giant cell-rich solitary fibrous tumour (GCR-SFT), previously referred to as giant cell angiofibroma, is an uncommon soft tissue tumour that classically occurs in the orbit but very rarely presents in deep organs. Here, we present a case of GCR-SFT occurring in the urinary bladder, which is one of the unusual histological subtypes of SFT.

Case presentation: A 56-year-old man was incidentally found to have a mass measuring 4.5 × 4.3 × 4.0 cm located in the left posterior wall of the bladder by computed tomography during a physical examination. The lesion was confirmed as GCR-SFT by pathological examination after laparoscopic radical surgery. Histopathologically, the tumour was a well-circumscribed, nonencapsulated lesion that was composed of bland spindle-ovoid tumour cells alternating with hypocellular and hypercellular areas, staghorn-like vasculatures and scattered large dark-stained multinucleate giant cells lining pseudovascular spaces. The spindle-ovoid cells and multinucleate giant cells showed strong and diffuse expression of CD34 and nuclear STAT6. In addition, the hallmark of the NAB2ex4-STAT6ex5 fusion gene was detected by RT‒PCR. The patient was classified as having a low risk of recurrence or metastasis according to the risk stratification criteria. The patient underwent regular follow-up for 34 months after surgery, and there was no evidence of local recurrence or metastasis.

Conclusion: This is the first reported case of GCR-SFT occurring in the urinary bladder with underlying NAB2ex4-STAT6ex5 fusion. Complete surgical excision of the tumour and long-term follow-up are recommended to ensure no local recurrence or metastasis.

Keywords: Giant cell-rich solitary fibrous tumour; NAB2-STAT6 gene fusion; Prognosis; Urinary bladder.

Fig. 1

Contrast-enhanced axial CT revealed a 4.5 × 4.3 × 4.0-cm soft tissue mass located in the left posterior wall of the bladder with a clear boundary and uneven density protruding into the bladder cavity

Fig. 2

Histopathological features of GCR-SFT. (A) The tumour was characterized by the presence of spindle- or ovoid-shaped cells among sparse collagen fibres (H&E, magnification×40). (B) Vessels were dilated, staghorn-like appearance with remarkable scattered multinucleate giant cells lining pseudovascular spaces (H&E, magnification×200). The tumour cells were strongly positive for CD34 (C) and nuclear STAT6 (D) (immunohistochemistry, magnification×200). (E) The NAB2ex4-STAT6ex5 fusion gene was revealed by RT‒PCR