Pitfalls in FNA diagnosis of warthin’s tumour

Abstract

Aim To illustrate an important potential diagnostic pitfall in salivary gland cytology. In particular, to demonstrate that acinic cell carcinoma can have an appearance indistinguishable from Warthin’s tumour, and should be considered in the differential diagnosis. Methods Corresponding cytology and histology findings are presented for a case of acinic cell carcinoma. Results A 78-year-old male presented with a right parotid swelling. Fine needle aspiration (FNA) showed features typical of a Warthin’s tumour with clusters of oncocytes in a background of small lymphocytes and granular debris. However, histological examination of the excision specimen showed an acinic cell carcinoma invading into surrounding fat and normal parotid. It had very prominent lymphoid stroma with germinal centres. Conclusions Acinic cell carcinomas often have very bland appearing nuclei and may have abundant granular or foamy cytoplasm. These features combined with the prominent lymphoid stroma that may be present in acinic cell carcinomas can easily be misdiagnosed as Warthin’s tumour on FNA and should therefore be considered in the differential diagnosis. It should be remembered that there are numerous neoplastic and non-neoplastic lesions that can give a similar cytological appearance to Warthin’s tumour. FNA results for salivary gland neoplasms should always be interpreted in conjunction with clinical and radiological features.