Extranodal follicular lymphoma: a clinicopathological and genetic analysis of 15 cases arising at non-cutaneous extranodal sites.

Abstract

Recent studies of primary cutaneous follicular lymphoma suggest that it represents a clinicopathological entity distinct from nodal follicular lymphoma (FL). The purpose of this study was to determine if FL arising at other extranodal sites is more closely related to FL occurring in the skin or in lymph nodes. Fifteen cases of non-cutaneous extranodal follicular lymphoma (ENFL) were identified from the Scotland and Newcastle Lymphoma Group (SNLG) database. All were stage 1E at presentation and involved the tonsil (n = 3), palate (n = 3), skeletal muscle (n = 2), ileum (n = 2), duodenum (n = 1), stomach (n = 1), thyroid gland (n = 1), submandibular gland (n = 1) and fallopian tube (n = 1). Polymerase chain reaction for t(14;18) using primers to the major breakpoint cluster region was performed on 14 cases of ENFL and the incidence of the translocation compared with that found in 16 cases of stage 1 nodal FL. Clinical and follow-up data were obtained from the SNLG database for the 15 cases of ENFL and 87 cases of stage 1 nodal FL, and a comparison of outcomes made. Only 2/14 cases of ENFL had detectable t(14;18) compared with 9/16 stage 1 nodal FL (P < 0.01). Freedom from progression and disease-specific survival was similar for the 15 cases of ENFL and 87 cases of stage 1 nodal FL. However, 13/15 patients with ENFL were disease free at the end of follow-up compared with 49/87 stage 1 nodal FL (P < 0.02). The low incidence of t(14;18) and favourable outcome encountered in ENFL in this study is similar to that previously found for primary cutaneous FL. These results support the concept of a subtype of FL lacking t(14;18) involving the major breakpoint cluster region, and with a propensity to arise at extranodal sites. Despite a high relapse rate, patients with ENFL are more likely to achieve complete remission and may ultimately have a more favourable long-term prognosis than those with equivalent nodal disease.