Follicular lymphoma presenting like marginal zone lymphoma: A case report

BACKGROUND: Follicular lymphoma (FL), a common type of indolent lymphoma, carries markers of the germinal center, and the rearrangement of the BCL-2 gene is regarded as an initiating event and a hallmark of the neoplasm. When FL has marginal zone differentiation, some marginal zone features are carried by the neoplasm. CASE SUMMARY: A 54-year-old male with lymphadenopathy, splenomegaly and hyperlymphocytosis was diagnosed with FL with marginal zone differentiation. The tumor demonstrated different features in the bone marrow (BM) compared with the follicle of the lymph node (LN). Some component of the neoplasm mimicked marginal zone lymphoma, such as infiltrating the marginal zone of the LN, displaying a monocytoid shape and lacking the expression of CD10 in the BM. The diagnosis of FL was made due to the concurrent detection of BCL-2 rearrangement in the LN and BM. CONCLUSION: Discordant pathological features in LN and BM could mislead diagnosis. When clinical and pathological manifestations are confusing in diagnosis, typical genetic abnormalities are decisive.