Nodular fasciitis in the parotid gland: a case report and review of the literature.

Nodular fasciitis (NF) is a benign, reactive lesion with a self-limiting process. Because NF is rare in the parotid gland and has many cytological similarities to other benign or malignant tumors, cytological misinterpretation is common. The patient, a 30-year-old woman, had a painless mass in her right parotid gland. Fine needle aspiration cytology (FNAC) was performed. Spindle cells with basophilic and well-demarcated cytoplasm were observed in a mucoid-like background. The mucoid-like substance was metachromatic and appeared to be the matrix of PA. Histopathologically, spindle-shaped cells with intervening birefringent mature collagen were arranged in short irregular bundles. Prominent mucoid-like matrixes as well as few infiltrating neutrophils and lymphocytes were found in the background. Lesional cells were positive for CD10 and β-catenin in the cytoplasm, but negative for cytokeratin, the S-100 protein, CD34, and neurofilament. Ultimately, this patient was diagnosed with NF. In FNAC of the parotid gland region, distinguishing NF from other real tumors is important for deciding treatment strategies.