Fine-needle aspiration findings in patients with polymorphous low grade adenocarcinoma of the salivary glands.

Background: Polymorphous low grade adenocarcinoma of the salivary glands (PLAC) is a low grade neoplasm that predominantly occurs in the minor salivary glands. In this site it is amenable to biopsy and histologic diagnosis. However, experience with fine-needle aspiration (FNA) biopsy findings in these tumors is limited. The authors describe the FNA cytology of this entity.

Methods: Fine-needle aspirates from two primary parotid and three metastatic PLACs were reviewed and correlated with their histology.

Results: All aspirates showed similar cytologic features, with hypercellular smears showing branching papillae, sheets and clusters composed of bland uniform cells with round-to-oval nuclei, dispersed chromatin, and absent or inconspicuous nucleoli. The cells generally had a scant-to-moderate amount of eosinophilic cytoplasm. Mitoses and nuclear pleomorphism were absent. These cells formed tubular structures containing hyaline globules in all cases and often a dispersed myxohyaline stroma. Bare nuclei also frequently appeared in the background. Two cases, which had prior histologic diagnoses, were diagnosed on FNA as metastatic PLAC. One metastatic case was diagnosed as benign metastasizing pleomorphic adenoma. One primary case was diagnosed as adenoid cystic carcinoma and one case as PLAC on FNA.

Conclusions: The cytologic differential diagnosis of PLAC includes adenoid cystic carcinoma, pleomorphic adenoma, and monomorphic adenoma. PLAC should be considered in the differential diagnosis of head and neck masses, where the cytology suggests one of these tumors, even when the clinical context (involvement of a major salivary gland, lymph node metastasis) is not typical of PLAC.