[Clinicopathological features and molecular genetics of paediatric-type follicular lymphoma: report of eight cases].

Objective: To investigate the clinical presentation pathological diagnostic features and molecular genetics of paediatric-type follicular lymphoma (PTFL). Methods: Eight cases of PTFL at Fujian Cancer Hospital between January 2003 and May 2018 were analyzed by hematoxylin-eosin stain, immunohistochemistry, polymerase chain reaction (PCR) and fluorescence in situ hybridization (FISH). The relevant literature review was performed. Results: All patients were male with age ranging from 12 to 27 years (median age of 18 years and average age of 19 years). Clinical manifestations included painless lymph adenopathy, primarily involving head and neck lymph nodes (6/8). According to Ann Arbor stage, there were 7 patients at stage Ⅰ A and 1 patient at stage Ⅱ A. Histologically, the structure of the lymph nodes was effaced with pushing borders visible at the tumor periphery. The lesions consisted of expanding, irregular follicles that were arranged in back to back fashion along with thinning or disappearing sleeves. The starry sky phenomenon in the follicle was prominent with loss of polarity. Under high power magnification, the follicles were composed of uniform, medium-sized blastic cells in 5 cases or centroblast in 3 cases. The neoplastic cells were positive for B cell markers and germinal center markers primarily confined to the germinal center. Bcl-2 was negative in 7 cases and 1 case showed weak bcl-2 staining. MUM1 was negative in all cases. Ki-67 demonstrated a high proliferation index of great than 70% in 7 of 8 cases. Eight cases showed Ig clonal rearrangement. No bcl-2, bcl-6, and IRF4/MUM1 gene rearrangements by FISH were detected in all cases. One patient was treated with 6 cycles of CHOP after surgical resection. Other patients underwent only simple surgical resection. All patients were alive upon clinical follow-up. Conclusion: PTFL is a rare subtype of B cell lymphoma with unique clinical and pathological features. It should be distinguished from reactive follicular hyperplasia, nodal marginal lymphoma in children, large B-cell lymphoma with IRF4 rearrangement and usual follicular lymphoma.