Low-grade papillary cystadenocarcinoma of the parotid gland: presentation of a case with cytological, histopathological, and immunohistochemical features and pertinent literature review.

Cystadenocarcinoma of the salivary glands is a very rare, slow growing, low-grade malignant neoplasm. However, when it occurs, it poses a diagnostic challenge. They are usually well circumscribed and exhibit multicystic appearance. The cytological features of fine-needle aspirates show bland appearing papillary and micropapillary neoplasm with variable cellularity and absence of cytological atypia. The cells are small to medium in size with abundant and occasionally vacuolated cytoplasm. The nuclei are eccentric, bland appearing, round, and at the most part uniform in size without anaplasia or mitotic activity. The background is commonly mucoid. Histologically, the neoplasm is usually well circumscribed and contains variably sized multicystic spaces with papillary structures. Foci of definite stromal invasion by tumor cells have to be present to justify the diagnosis of carcinoma. The remainders of the cytological features are similar to these seen on cytological smears. Typically, they are slow growing and conservative, but complete surgical excision is considered adequate. We present a case in a 57-year-old Saudi man that we believe the first from our region demonstrating the clinical and pathological features.