A case of giant cell‐rich solitary fibrous tumor in the external auditory canal

Abstract

We present a rare case of giant cell-rich solitary fibrous tumor (SFT) arising at the left external auditory canal in a 31-year-old woman. The tumor was well-circumscribed and composed of spindle-shaped cells with abundant collagenous bands. Scattered multinucleate giant cells were observed, some of which lined pseudovascular spaces. Although a focal mild-hypercellular area was observed, mitoses were rare and necrosis was absent. Interstitial mast cells were scattered, especially in the hypercellular area. Immunohistochemically, CD34, vimentin, and Bcl-2 presented diffuse positivity. Moreover, both mononuclear spindle cells and multinucleate cells showed nuclear STAT6 positivity, while NAB2-STAT6 fusion gene could not be detected by reverse transcription polymerase chain reaction using formalin-fixed specimen. These findings suggest the pathological diagnosis of giant cell-rich SFT, previously known as giant cell angiofibroma, which is a rare variant of SFT with multinucleate giant cells and occurs predominantly in orbital region. Although giant cell-rich SFTs of extra-orbital sites have been reported, to our knowledge, this is the first case arising in the external auditory canal. Giant cell-rich SFT should be considered as a differential diagnosis of spindle cell lesion with multinucleate giant cells, and STAT6 immunohistochemistry should be performed to distinguish this rare tumor from other mesenchymal neoplasms.

Solitary fibrous tumor

“…Fat production is seen in approximately 8% of tumors (32). Focal or extensive myxoid change or multinucleated giant cells also may be observed (33,34).…”

Orbital solitary fibrous tumors: a multi-centered histopathological and immunohistochemical analysis with radiological description

“…18 Furthermore, giant cellrich SFTs ( previously known as giant cell angiofibromas) have been described in multiple studies as a spindleshaped cell on a ground of thick collagen with multiple multinucleated giant cells; this was observed in two of our cases. 5,19 Lacrimal gland SFTs might have some additional histopathological feature that has been also described in SFT involving the salivary gland(s), which is the entrapment of the gland tissue with dilated ductal structures, which might be similar in appearance to pleomorphic adenoma.5 Feasel et al analyzed 26 superficial solitary fibrous tumors for pathological studies. 20 Most of their cases (70%) were in the cellular end of the spectrum which also featured irregular fascicles of spindled cells with staghorn-like vessels and variable amounts of collagen.…”

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“…It belongs to a spectrum of mesenchymal tumors, including hemangiopericytoma (HPC) [2,3]. In the head and neck region, SFT has been described in the oral cavity [4], ear [5], nasal cavity and para-nasal sinuses [6], orbit [7], parotid gland, and soft tissue [8], whereas it is rare in the larynx. Both clinical and radiologic findings are nonspecific, making the histological assessment key in the diagnosis, based on architectural, cytomorphological, and immunohistochemical findings [8,9].…”