Flow cytometry significantly improves the diagnostic value of fine needle aspiration cytology of lymphoproliferative lesions of salivary glands

Abstract

Objective: Lymphoid proliferations of the salivary glands can be either reactive or malignant. Diagnosis based solely on fine needle aspiration (FNA) cytology may be troublesome in view of the difficulty in distinguishing low-grade B-cell and mucosa-associated lymphoid tissue (MALT) lymphomas from reactive lymphoid proliferations. We report our experience with FNA cytology combined with flow cytometry (FC) immunophenotyping for the diagnosis of lymphoproliferative processes affecting the salivary glands.

Methods: Sixty-one FNA specimens, obtained from salivary glands over a 10-year period, were analysed by cytology and FC. The results were correlated with histological follow-up if available.

Results: A diagnosis of lymphoma was given in 37 of 61 (61%) specimens; 22 of 61 (36%) specimens were considered as benign/reactive or non-lymphomatous processes; two of 61 (3%) specimens were considered as suspicious for lymphoma on cytological analysis and negative on FC. Histological control was available in 23 malignant, four non-lymphomatous and one cytologically suspicious case. Data obtained by the combination of cytology and FC were confirmed in all but one case: the case suspicious on cytology received a histological diagnosis of carcinoma. Four of seven cases with small populations of clonal cells (less than 15%) were histologically confirmed as lymphoma, whereas two remain under surveillance and one was reactive. Correlation with histological data showed a sensitivity of 100% and a specificity of 83% for the combination of cytology and FC.

Conclusions: FC is fundamental for the diagnosis of lymphoproliferative lesions of the salivary glands. It may solve cytologically suspicious cases and detect the presence of neoplastic B or T cells. This combined approach reduces the time to therapy and may prevent unnecessary surgical biopsies.

Keywords: fine needle aspiration cytology; flow cytometry; lymphoproliferative disease; mucosa-associated lymphoid tissue lymphoma; non-Hodgkin lymphoma; salivary glands.