A case of nodular fasciitis that was difficult to differentiate from a parotid tumor

Abstract

A 48-year-old male presented with swelling in the left parotid gland. Ultrasonography and contrast-enhanced CT revealed an approximately 4-cm mass in the left parotid gland with an indistinct border to the masseter muscle. The patient was referred to our hospital for further examination and treatment. Contrast-enhanced MRI revealed a lobulated mass with equal signal intensity to skeletal muscle on T1-weighted images and high signal intensity on T2-weighted images. A needle biopsy revealed no atypical cells. Partial excision of the left parotid gland, specifically the shallow lobe, was performed to differentiate between polymorphous adenoma and malignancy. The lesion was located in the shallow lobe of the parotid gland and was partially adherent to the masseter muscle at a deeper level, prompting partial excision of the masseter muscle. Fasciitis nodosa was diagnosed based on pathological findings, including immunostaining. Fasciitis nodosa is a benign disease that can be difficult to distinguish from malignancy because of its sudden enlargement and unclear boundaries with the surrounding tissues. Nodular fasciitis should be differentiated from nodular fasciitis in the presence of a parotid mass with indistinct borders to avoid complications from an enlarged resection.