Striated duct adenoma: The cytological description of a rare entity

Striated duct adenoma is a benign salivary gland tumour recently recognized by the World Health Organization. To date, no report has described the cytological features of this entity.

We report the case of a 60-year-old woman with a tumour in the right parotid gland with a diameter greater than 2.4 cm confirmed by imaging tests.

Two fine-needle aspiration cytologies (FNAC) were performed with inconclusive results, reporting epithelioid and spindle-shaped cellularity, with little stroma, and nuclei with abundant pseudoinclusions. Myoepithelioma and Schwannoma were proposed as differential diagnoses. An immunocytochemical panel was performed, showing positivity for S-100, SOX10, CK7 and vimentin, and negativity for both myoepithelial (p63 and calponin) and thyroid markers. In the absence of a conclusive diagnosis, the patient accepted surgery. The biopsy results confirmed diagnosis of striated duct adenoma, with immunohistochemical features superimposable to cytology.

Little information is available in the literature, both on biopsy and, more strikingly, on cytology of this neoplasm. The aim of this work is to provide cytological characteristics that allow diagnosis of this entity with FNAC and thus avoid unnecessary surgeries.