Study of Extramedullary Lymphoblastic Lymphoma (LBL) Diagnosed by Flowcytometric Immunophenotyping (FCI) on Fine Needle Aspirate (FNA) Sample-A Case Series of 18 Cases.

Background: Lymphoblastic lymphoma (LBL) accounts for about 2% of all lymphomas. Recognition of T/B-LBL albeit of their rareness is very important as they present as localized diseases with low tumor burden. They can present both at nodal and extranodal sites. Limitation of diagnosis and classification of lymphoma on fine needle aspirate (FNA) can be minimized by clubbing it with flowcytometric immunophenotyping (FCI) to ensure diagnostic accuracy rapidly.

Aim: Study of a series of 18 cases of LBL to assess the utility of FCI on FNA and effusion samples in extramedullary LBL.

Methods and material: FCI was done on FNA and effusion samples from 130 morphologically diagnosed/suspicious cases of lymphoreticular malignancy, followed by peripheral blood and bone marrow (BM) examination. The patients diagnosed to have B/T LBL, based on WHO 2017 classification, were selected for further analyses.

Results: FCI of 130 cases showed 91 mature and 18 precursor lymphoid neoplasms. These 18 cases were from lymph nodes (11), pleural fluid (03), and soft tissue masses (04). Peripheral blood and BM of 15/18 cases were normal of which FCI revealed T-LBL (11) and B-LBL (04). Two cases (both T LBL) showed BM involvement (<25%), while one case of B-LBL which was misdiagnosed as mature lymphoma by immunohistochemistry (IHC) evolved as B ALL.

Conclusions: Diagnosis of extramedullary B/T-LBL needs comprehensive evaluation of clinical presentation, cytomorphology, and immunophenotyping. Rapid and accurate diagnosis by FCI on FNA and effusion samples allows early therapeutic decisions, thereby avoiding leukemic dissemination.