Is a Solitary Fibrous Tumor in the External Auditory Canal Benign?

Abstract

A solitary fibrous tumor (SFT) is an extremely rare, distinct otological soft-tissue tumor. Only two such tumors in the external auditory canal have been reported. A SFT related to hemangiopericytomas (HPC), which commonly arise in the central nervous system. HPCs act malignant in many cases, while SFTs at other sites are mainly benign. A 25-year-old female presented with highly vascular tumor at the right external auditory meatus and bleeding from the mass when a crust was removed from its surface. After excisional biopsy followed by pre-operative embolization, this tumor confirmed with SFT. The recurrence rate of SFT is very low after complete resection, with a slightly increased risk of recurrence with extrathoracic tumors. We describe the third case of SFT in the external auditory canal and review the literature.

Keywords: External auditory canal; Hemangiopericytoma; Solitary fibrous tumor.

Fig. 1. A: A small, ulcerated, skin-covered mass (arrow) on the posterosuperior wall partially blocking the entrance of the external auditory canal. B: Contrast-enhanced CT showed a round hyperattenuated mass (arrow) with no clear invasion of adjacent structures. C, D: Four-vessel angiography was used to find and embolize the feeding artery, the posterior auricular artery. C: Round dark mass (arrow) before shutting off. D: Faint mass shadow (arrow) after shutting off.

Fig. 2. Histological and immunohistochemical findings of the solitary fibrous tumor. Well-circumscribed, non-encapsulated spindle-cell tumor located in the dermis (A) (H&E, ×10). The tumor had a patternless architecture of hypo- and hypercellular areas separated by thick, hyalinized collagen with cracking artifact and staghorn vessels (B) (H&E, ×40). Fibroblast-like cells with bland nuclear features, mixed with thick bands of collagen (C) (H&E, ×200). The spindle cells are positive for CD34 (D) (×200), and partially positive for bcl2 (E) (×200) and CD99 (F) (×200).