Extranodal diffuse large B cell lymphoma of cutaneous follicle centre lymphoma type: a study of 24 patients with non-cutaneous primary limited stage extranodal diffuse large B cell lymphoma in support of a new concept

Aims: Follicle centre cell lymphoma of small cell type showing either a follicular or diffuse growth pattern similar to cutaneous follicle centre lymphoma (cFCL) has been recognized in extranodal non- cutaneous sites. Our aim was (i) to investigate whether diffuse large B cell lymphoma (DLBCL) of cFCL type could be identified in extranodal non- cutaneous sites and (ii) whether clinical characteristics similar to primary cFCL could be recognized. Methods and results: Of 24 extranodal non- cutaneous DLBCLs, nine (38%) had large centrocytoid morphology and 15 (62%) were either ` centrocytoid and centroblastic' or ` centroblastic and immunoblastic'. Six centrocytoid cases were Irf-4 negative, Bcl-6 positive and at most weakly CD10-or Bcl-2-positive by immunohistochemistry, consistent with DLBCL of cFCL type. All patients with cFCL type were stage IE and were significantly younger than other patients. Recurrences occurred in two patients and were exclusively extranodal. Conclusion: Our results suggest that DLBCL of cFCL type can be identified in extranodal non-cutaneous sites and shows clinical characteristics similar to genuine cFCL. We propose to expand the concept of cFCL to encompass large cell lymphomas in extranodal sites.