Clinical observation of pediatric-type follicular lymphomas in adult: Two case reports

Pediatric-type follicular lymphoma (PTFL) is a unique pathological type in the 4^th edition of hematopoiesis and lymphoid tissue tumor classification revised by World Health Organization. It is unique in clinical practice and seldom seen in adult. PTFL mainly occurs in the head and neck lymph nodes. Most of the cases are short of fever, night sweat, weight loss, and other B symptoms which substitute for lymphadenopathy as the main symptom. PTFL can be disposed of surgical resection and it can achieve long-term tumor-free survival, and it has an excellent outcome.

Two cases of PTFL were reported and their clinicopathological features, differential diagnosis, therapy and prognosis were discussed. PTFL showed gray-brown tough texture in general performance. The histological manifestations of PTFL were similar to that of adult-follicular lymphoma (FL). Under low power microscope, the structure of lymph nodes was destroyed in different degree, the follicles were closely arranged, expanded and irregular, and the mantle zone became thin or disappeared. In addition, the "starry sky phenomenon" could be seen. At high magnification, the follicles were mainly composed of single medium-sized central cells, and some of them mainly consisted of centroblastic cells to characterize scattered chromatin and inconspicuous nucleoli. Immunohistochemical showed the tumor cells expressed CD20, PAX5, CD79a and CD10, BCL6, FOXP-1, which were limited in germinal center; Ki-67 was highly expressed in germinal center. CD21 and CD23 showed nodular and expanded follicular dendritic cells. Immunoglobulin gene rearrangement was positive for IGH and IGK. The two patients underwent surgical resection with no complications. After discharge, the two patients with a close review for 18 mo and 5 mo respectively and showed no evidence of recurrence.

PTFL in adult is generally supposed to be extremely rare. PTFL displayed characteristic morphological, immunophenotypic, and molecular biological changes which are a kind of neoplasm with satisfactory prognosis after surgical excision.