Abstract
Herein, we report a diagnostically challenging case of a B-cell lymphoma initially masquerading as pure red cell aplasia (PRCA). The key to diagnosis was the unique finding of phagocytic activity (engulfing erythrocytes and lymphocytes) by atypical mature lymphocytes in both peripheral blood and bone marrow, accompanied by clinical signs of cold agglutination. Despite inconclusive initial morphology for lymphoma and a bone marrow erythroid count that did not fully meet PRCA criteria, flow cytometric immunophenotyping confirmed a clonal B-cell population. This case underscores that lymphocyte-mediated phagocytosis is a highly suggestive, albeit rare, indicator of malignancy and can serve as a pivotal clue to uncover an underlying lymphoma obscured by autoimmune phenomena like PRCA.