Aim and introduction: Pediatric nodal marginal zone lymphoma (NMZL) is a rare, but distinct subtype of NMZL with characteristic clinical presentation, pathohistological and molecular features, therapy and prognosis. Results: We report the case of a 15-year-old boy with no remarkable past history, presented with painless enlargement of left submandibular lymph node (LN) for three months. He was admitted to the University Children’s Hospital in Belgrade in May 2016. The cervical ultrasound demonstrated moderate left submandibular lymphadenopathy, but also mild enlargement of two right submandibular LNs (17x7mm, 14x7mm). Physical examination, chest radiography and abdominal ultrasound revealed no hepatosplenomegaly and lymphadenopathy elsewhere. The result of blood count test was normal. Biochemistry showed elevated uric acid 499 umol/l, AST 45U/l, ALT 98U/l, and sedimentation rate (65mm/h). Urea, creatinine, alkaline phosphatase, LDH and CRP were normal. The patient underwent left submandibular LN excisional biopsy. The size of the LN was 47x37x20mm. The histopathological examination revealed partial architectural effacement: follicular hyperplasia and nodular B-cell infiltration with features of progressive transformation of germinal centers (PTGC) in the form of fragmentation of follicles. A CD20 immunostain shows an abnormal expansion of the marginal zone with infiltration of interfollicular space. These B-cells were negative for CD3, CD5, CD23, EBV-LMP1, bcl-6, CD10, EMA, CD30, CD15, MUM-1, and positive for bcl-2 and IgD. A CD21/ CD23/ fascin immunostain showed an expanded and disrupted follicular dendritic cell meshwork. Ki-67 highlighted residual follicular polarisation and a low proliferation rate in the interfollicular areas. Based on these pathohistological findings it was concluded that LN likely represent reactive follicular hyperplasia with atypical marginal zone hyperplasia or possible PNMZL, with APSTRAKTI 95 MATERIA MEDICA • Vol. 34 • Issue 1, suplement 1 • april 2018. recommendation of polymerase chain reaction (PCR) analysis of clonality. Additional IGH PCR analysis demonstrated biclonal heavy chain gene rearrangement. These findings were consistent with PNMZL. After consultation with members of International BFM study group for non-Hodgkin lymphomas, followup was recommended without any treatment. The patient has remained disease free for 22 months since diagnosis. Conclusion: We presented a rare case of PNMZL with morphological features of PTGC, but immunohistochemistry and additional PCR clonality analysis were crucial for final diagnosis. This case represents a diagnostic and therapeutic challenge because of their rarity in the pediatric population.

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