Aberrant Expression of Multiple T-Cell Markers in Primary Cutaneous Follicle Center Lymphoma: A Rare Case Report.

Aberrant expression of T-cell markers in B-cell lymphomas is rare and can pose diagnostic challenges. We report a case of a 65-year-old man presenting with newly developed scalp nodules. Histopathology revealed nodular lymphoid infiltrates composed of large centrocytes and centroblasts. Immunohistochemistry demonstrated CD20, BCL6, CD10, and MEF2B positivity with monotypic kappa light chain expression, confirming B-cell lineage. Notably, aberrant co-expression of multiple T-cell markers (CD2, CD3, CD4, and partial CD5), with weaker intensity than surrounding T-cells, was observed. Molecular studies showed clonal immunoglobulin heavy chain rearrangement with a polyclonal T-cell receptor pattern. These findings established the diagnosis of primary cutaneous follicle center lymphoma (PCFCL) with aberrant T-cell marker expression. This represents the first reported case of PCFCL with aberrant expression of multiple T-cell markers, emphasizing the importance of comprehensive immunophenotyping for accurate lymphoma classification.