The role of SOX11 immunostaining in confirming the diagnosis of mantle cell lymphoma on fine-needle aspiration samples

BACKGROUND Mantle cell lymphoma (MCL) demonstrates cytologic features that overlap with those of other types of B-cell non-Hodgkin lymphomas (B-cell NHLs) containing small to medium-sized cells. The accurate diagnosis of MCL is important because MCL has relatively more aggressive biologic behavior and thus requires specific treatment regimens. Fine-needle aspiration (FNA) is used for diagnosing or staging lymphoma, often with the help of immunophenotyping by flow cytometry. However, the cellularity of an FNA sample may not be high enough for flow cytometry, leading to diagnostic difficulty. SOX11 immunostaining is helpful in the diagnosis of MCL in histologic sections. However, to the authors' knowledge, its diagnostic value for FNA samples has not been studied to date. METHODS Immunostains for SOX11 were performed on 69 FNA cases with final diagnoses of MCL (13 cases, including 10 classic type and 3 blastoid variant), marginal zone lymphoma (8 cases), follicular lymphoma (10 cases), small lymphocytic lymphoma (12 cases), Burkitt lymphoma (9 cases), plasma cell myeloma (7 cases), and benign lymph nodes (10 cases). Preparation types included cytospin slides (65 cases), direct smears (2 cases), and cell block sections (2 cases). The percentage of positive cells (defined as nuclear staining) and staining intensity were recorded. RESULTS All 13 cases of MCL were positive for SOX11 staining, with 12 cases demonstrating diffuse positivity. All other types of B-cell NHL cases, plasma cell myelomas, and benign lymph nodes were found to have negative results. Weak staining was found in 1 MCL case of blastoid variant. CONCLUSIONS SOX11 immunostaining on FNA samples is highly sensitive and specific for MCL and can be used as a reliable adjunct to confirm MCL, especially in a recurrent setting.