Solitary fibrous tumour of the submandibular gland: Novel insights from clinical practice on a close mimicker of pleomorphic adenoma and a diagnostic challenge for the cytopathologist

Abstract

Spindle cell lesions of the salivary glands are rare and account for less than 3% of the salivary gland aspirates. A definitive classification of salivary gland neoplasms by fine needle aspiration is possible for the most common lesions but remains a challenge for the less common entities. We present a case of a 72‐year‐old male with a solitary fibrous tumour (SFT) of the submandibular gland mimicking a myoepithelial‐rich pleomorphic adenoma (PA). In this article, we discuss novel insights that help differentiate SFT from PA and other spindle cell lesions.

Cytomorphological spectrum of solitary fibrous tumour: revisited

“…Bcl‐2, CD99, EMA, vimentin and TLE are other positive ICC markers. S‐100, desmin, SMA, SOX10, CD31 and cytokeratin stain negative 35 . However, these are non‐specific markers as they stain positive in other tumours as well.…”

“…Hence, these entities have been reported as spindle cell neoplasms or simply mesenchymal lesions. A careful search for characteristic morphological features should always be undertaken to improve the diagnostic efficacy of FNA for SFTs 35 …”

“…15 It is not unusual to find atypical cells in cytology smears of benign SFTs; these should be interpreted with caution to avoid a false positive diagnosis. 13,31,32,34,35 Further, smears may frequently show a combination of several findings. Also, the cell block sections can simulate the "patternless" haphazard arrangement seen on histopathology.…”

“…S-100, desmin, SMA, SOX10, CD31 and cytokeratin stain negative. 35 However, these are non-specific markers as they stain positive in other tumours as well.…”

“…A careful search for characteristic morphological features should always be undertaken to improve the diagnostic efficacy of FNA for SFTs. 35 The…”