Basal cell carcinoma metastatic to the salivary glands: differential diagnosis in fine-needle aspiration cytology.

A disparate group of salivary gland neoplasms is characterized by small, uniform, hyperchromatic, basaloid cells. This "small blue cell" pattern is most common in non-Warthin's types of monomorphic adenoma, or in adenoid cystic carcinoma. Small cell anaplastic carcinoma (primary or metastatic), metastatic basaloid squamous cell carcinoma, basal cell adenocarcinoma, and metastatic nasopharyngeal carcinoma are rarely encountered but may present a cytologically similar appearance. We report one female and two male patients (median age = 84 yr) with cutaneous-type basal cell carcinoma (BCC) aspirated from metastatic deposits in the parotid (2 cases) or the submandibular (1 case) gland. One was correctly classified at the time of aspiration, based on a previous history of multiple facial BCC. One was interpreted as carcinoma, the previous history being unavailable at the time of FNA. Smears in these two cases show necrosis and rare keratotic cells. The third cases was mistaken for pleomorphic adenoma (PA); the smears showed metachromatic fragments of collagenous tumor stroma that were misinterpreted as the matrix material typical PA. Similar material was identified in the other two cases. When the "small blue cell" pattern is encountered in salivary bland cytology, one should consider BCC, especially if necrosis is identified. The desmoplastic tumor stroma of BCC may mimic the chondroid matrix of PA. Careful consideration of previous history is very important.