Challenges in the cytological diagnosis of nodular fasciitis

Abstract

Nodular fasciitis (NF) is a self-limiting neoplasm found in the upper extremities, trunk, head, and neck. NF occurring in the tragus is extremely rare. Its rapid growth and hypercellularity on cytology can mimic malignancy causing diagnostic challenges. Here we present a case of a 39-year-old female presented with a rapidly growing 2×2 cm firm swelling on the right tragus. FNAC showed a cellular lesion with fibroblast-like spindle cells and myofibroblasts in a myxoid background with occasional multinucleated cells, suggesting a benign mesenchymal lesion, likely NF. Surgical excision was performed and histopathology confirmed the diagnosis. The exact aetiology is not known. However, NF is associated with recurrent MYH9:USP6 gene fusions. FNAC smears show hypercellularity with spindle cells, myxoid background, and occasional nuclear overlapping, often leading to confusion with sarcoma.FNAC is a simple, cheaper and minimally invasive diagnostic modality which helps in the diagnosis yet its variable and nonspecific cytomorphologic features at times can lead to misdiagnosis. This case report highlights the diagnostic challenges associated with NF, particularly due to its unusual location in the tragus.