Primary cutaneous follicular lymphoma: A clinicopathologic and molecular study of 16 cases in support of a distinct entity

Primary cutaneous B-cell lymphomas displaying a prominent follicular growth pattern are rare and remain poorly defined, particularly in terms of the frequency of detection of t(14;18) and whether or not, as a group, they represent an entity distinct from follicular lymphoma arising in lymph nodes. The morphologic, immunophenotypic, and clinical features of 16 cases of primary cutaneous follicular lymphoma, identified during a review of all PCBCL in the Scotland and Newcastle Lymphoma Group database, were studied and the number of cases harboring t(14;18) assessed by polymerase chain reaction using primers to the major breakpoint cluster region. Comparisons were made with stage I follicular lymphoma arising in lymph nodes and follicular lymphoma secondarily involving the skin. All cases of primary cutaneous follicular lymphoma had undergone thorough staging, including physical examination and CT scans of chest and abdomen, with 15 of 16 cases also having bone marrow aspiration and/or trephine performed. The morphology and immunophenotype of the lesions were similar to that expected in lymph nodes. All cases displayed a follicular architecture complete with follicular dendritic cell networks and comprised an admixture of CD10 and/or bcl-6-positive neoplastic centrocytes and centroblasts with 13 of 16 cases also expressing bcl-2 protein. None harbored t(14;18), a significantly different finding compared with cases of stage I nodal follicular lymphoma (p