Solitary fibrous tumor of deep parotid gland preoperatively classified as salivary gland neoplasm of uncertain malignant potential by the Milan system for reporting salivary gland cytopathology: A common diagnosis for a rare entity

Abstract

Solitary fibrous tumor (SFT) is a rare fibroblastic tumor with spindle cell morphology, which is characterized by a prominent branching vasculature and a NAB2‐STAT6 gene rearrangement. SFT may occur in any anatomical site and may involve salivary glands, including the parotid gland. We present a young female with a primary parotid SFT diagnosed as “neoplasm—Salivary gland neoplasm of uncertain malignant potential (SUMP)” per the Milan system for reporting salivary gland cytopathology by fine‐needle aspiration (FNA) with surgical pathology follow‐up. Cytomorphology of SFT is diverse and overlaps with more common entities causing a diagnostic challenge. Non‐diagnostic FNA results are not uncommon. Thankfully, the majority of SFTs involving the salivary gland can be identified as “neoplasm” on FNA. The Neoplasm‐SUMP subcategory is considered for the majority of cases, which would warrant a diagnostic excision with clear surgical margins, which is also curative in most cases. The Neoplasm‐SUMP also perfectly encompasses the neoplastic behavior of SFT, which runs on a scale from indolent to malignant.