Pediatric-type follicular lymphoma and pediatric nodal marginal zone lymphoma are pediatric B cell lymphomas with similar clinical characteristics but distinct histological features. We investigated the differences between pediatric-type follicular lymphoma and pediatric nodal marginal zone lymphoma by comparing their histological and molecular characteristics. A total of 5 pediatric-type follicular lymphoma and 11 pediatric nodal marginal zone lymphoma patients were included in the study. In the histological review, 5 of the 16 cases showed overlapping morphological features of pediatric-type follicular lymphoma and pediatric nodal marginal zone lymphoma; hence, they were reclassified as \"mixed type.\" In molecular analysis, using panel-based massively parallel sequencing, MAP2K1, TNFRSF14, and IRF8 mutations were found in 6, 3, and 2 of the 11 pediatric nodal marginal zone lymphoma patients, respectively, and IRF8 mutation was found in one of the five pediatric-type follicular lymphoma patients. There were no significant differences in genetic alterations established from the histologically reclassified diagnosis as well as the initial diagnosis. Pediatric-type follicular lymphoma and pediatric nodal marginal zone lymphoma showed morphological overlap in some cases, and no difference between the two was found upon molecular analysis. These findings suggest the possibility that pediatric-type follicular lymphoma and pediatric nodal marginal zone lymphoma are single entity pediatric B-cell lymphoma with broad morphological spectrum.

Pediatric-type follicular lymphomas are rare lymphomas, affecting mostly children and young adults. These are characterized by an excellent prognosis, despite their conservative therapeutic approach. Recognized as an entity in the most recent 2016 WHO classification of tumors of hematopoietic and lymphoid tissues, its diagnosis is based on the recognition of an exclusively nodular architecture, thus conditioning the possibility of a cytological diagnosis. It is thus not odd, the scant literature found on the cytological approach to these lesions. Herein we describe a case of a pediatric-type follicular lymphoma, first approached through fine needle biopsy. The case is thoroughly discussed from a cytologic, immunophenotypic, and molecular point of view. Differential diagnoses are discussed. The final diagnosis was performed on histology.

Lymphoid and histiocytic lesions of the head and neck in pediatric patients is a fascinating topic as most of these lesions are benign, but that the neoplastic cases are essential to diagnose accurately for appropriate treatment. It is thought that 90% of children will have palpable lymph nodes between the ages of 4 to 8; most, but not all, are non-malignant and some resolve spontaneously without treatment. This paper will look at many of the benign and malignant lesions of both lymphocytic and histiocytic origin that present in the head and neck of children focusing on their diagnostic criteria. There is a very pertinent discussion of nonmalignant lymphoid proliferations, as infections and other reactive conditions dominate the pathology of pediatric lymphohistiocytic head and neck lesions. Discussion of those lymphomas which arise more frequently in the head and neck focuses on those seen in children and young adults such as classic Hodgkin lymphoma and Burkitt lymphoma, as well as new more controversial entities such as pediatric-type follicular lymphoma. Histiocytic lesions, both benign and malignant, are described and may be challenging to diagnose.

The aim of this study was to review the histopathological, phenotypic, and molecular characteristics of pediatric-type follicular lymphoma (PTFL) and to assess the diagnostic value of novel immunohistochemical markers in distinguishing PTFL from follicular hyperplasia (FH). A total of 13 nodal PTFLs were investigated using immunohistochemistry, fluorescence in situ hybridization (FISH), and PCR and were compared with a further 20 reactive lymph nodes showing FH. Morphologically, PTFL cases exhibited a follicular growth pattern with irregular lymphoid follicles in which the germinal centers were composed of numerous blastoid cells showing a starry-sky appearance. Immunohistochemistry highlighted preserved CD10 (13/13) and BCL6 (13/13) staining, CD20 (13/13) positivity, a K light chain predominance (7/13), and partial BCL2 expression in 6/13 cases (using antibodies 124, E17, and SP66). The germinal center (GC)-associated markers stathmin and LLT-1 were positive in most of the cases (12/13 and 12/13, respectively). Interestingly, FOXP-1 was uniformly positive in PTFL (12/13 cases) in contrast to reactive GCs in FH, where only a few isolated positive cells were observed. FISH revealed no evidence of BCL2, BCL6, or MYC rearrangements in the examined cases. By PCR, clonal immunoglobulin gene rearrangements were detected in 100% of the tested PTFL cases. Our study confirmed the unique morphological and immunophenotypic features of PTFL and suggests that FOXP-1 can represent a novel useful diagnostic marker in the differential diagnosis between PTFL and FH.

Objective: To investigate the characteristics in pathological diagnosis, clinical features, treatment and prognosis of adult patients with pediatric-type follicular lymphoma (PTFL) . Methods: The clinical and pathological features, laboratory examination, diagnosis and treatment, follow-up results of 5 adult PTFL patients admitted in Jiangsu Province Hospital were retrospectively analyzed, and literature review was conducted in combination with related reports. Results: All 5 patients developed PTFL in their adulthood with a median age of 22 years old (15-33 years) . The initial inanifestation of the disease was local painless lymphadenopathy with no fever, night sweats, emaciation or other systemic B symptoms. Pathological characteristics including typical large follicular structures and high proliferation index were found. Meanwhile, additional clonal rearrangement of immunoglobulin heavy chain gene was observed. However, there was no BCL-2 expression in histochemistry as well as BCL-2 gene abnormality in fluorescence in situ hybridization among these PTFL patients. These adult PTFL patients were all in stage Ⅰ-Ⅱ of the disease. For treatment, they were only treated with local surgical excision after diagnosis while didn\'t receive subsequent local radiotherapy or systemic immunochemotherapy. During a median follow-up of 27 months, the 5 cases of PTFL kept in a state of sustained complete remission. Conclusion: Adult-onset PTFL is characterized by high pathological proliferation index, while no BCL-2 expression or BCL-2 gene abnormality. Besides, PTFL is clinically manifested as a localized disease that can achieve a quite good prognosis through local surgical intervention. The aforementioned attributes of PTFL are distinctly different from classic adult follicular lymphoma.
目的： 探讨成人儿童型滤泡淋巴瘤（PTFL）患者的病理诊断、临床特征、治疗及转归特点。 方法： 回顾性分析在江苏省人民医院就诊的5例成人PTFL患者的临床病理特点、实验室检查、诊治经过及随访结果，并结合文献进行综述。 结果： 5例PTFL患者均为成年发病，中位年龄22（15~33）岁。起病时表现为局部无痛性淋巴结肿大，无发热、盗汗、消瘦等全身B症状。组织病理表现为典型的大滤泡结构，增殖指数高，存在免疫球蛋白重链基因克隆性重排，组化提示无BCL-2蛋白表达，荧光原位杂交未见BCL-2基因异常。所有患者均为Ⅰ~Ⅱ期，治疗仅通过局部肿块切除，未追加局部放疗或全身系统性免疫化疗。中位随访27个月，5例患者均处于持续缓解状态。 结论： 成人PTFL病理增殖指数较高，无BCL-2表达和基因异常，临床多为局限病变，通过局部手术治疗预后较好，与经典成人滤泡淋巴瘤有显著差异。.

BACKGROUND: Primary central nervous system lymphoma (PCNSL) is a relatively common tumor of the central nervous system. Although PCNSLs generally arise from the parenchyma, lymphomas arising primarily from the dura are termed dural lymphomas (DLs). Mucosa-associated lymphoid tissue is the most unique histological feature of DLs. Because of its rarity, the clinical characteristics of and treatments for DL have not been fully elucidated to date.
METHODS: A 31-year-old man with no past medical history presented with numbness in his left upper limb. Magnetic resonance imaging revealed a dural-based tumoral lesion and cervical lymphadenopathies. The lesion was diagnosed radiologically as a meningioma, and tumor resection was planned. However, an intraoperative pathological diagnosis showed neoplastic lymphocytes, and the planned total tumor resection was halted. Histologically, the tumor was characterized by areas of poorly defined follicular architecture consisting of medium and large centroblasts. These tumor cells were immunohistologically positive for CD10 and CD20 and negative for B-cell lymphoma (BCL) 2 and BCL6. Fluorescence in situ hybridization did not show evidence of an Immunoglobulin H/BCL2 fusion. The lesion was subsequently diagnosed as a pediatric-type follicular lymphoma (PTFL). Six cycles of R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone) plus 2 cycles of rituximab were administered. The patient showed no evidence of relapse at 12 months after diagnosis, and follow-up was ongoing at the time of this report.
CONCLUSIONS: This very rare case of DL was originally diagnosed as a PTFL. The tumor could be treated by immunochemotherapy alone.

Indolent lymphomas in the pediatric population were discussed during the 2014 European Association for Haematopathology/Society of Hematopathology workshop in Istanbul, Turkey. This session was focused on pediatric-type follicular lymphoma (FL), and its differential diagnosis with the newly recognized entity of IRF4/MUM1+ lymphomas mainly involving Waldeyer\'s ring. The differential diagnosis between t(14;18) negative FL grade 1/2 and pediatric-type FL in adults was highlighted. The overlapping pathological and clinical features between FL and nodal marginal zone lymphoma (NMZL) in children and young adults were recognized and morphologic and immunophenotypical criteria helpful for the differential diagnosis were presented. Both pediatric-type FL and NMZL are indolent processes that should be distinguished from atypical lymphoid hyperplasia of the tonsils and lymph nodes. The demonstration of a B cell monoclonal population by molecular studies is strongly recommended for the diagnosis. Recognition of these indolent variants to avoid overtreatment was emphasized. Whereas most indolent lymphomas in the pediatric population show characteristic clinical, pathologic, and genetic features that differ from the adult counterpart, other rare indolent lymphoid tumors such as chronic lymphocytic leukemia (CLL) have similar characteristics. In this report, novel findings, areas of special interest, and diagnostic challenges emerging from the cases submitted to the workshop will be discussed.