PEDIATRIC-TYPE FOLLICULAR LYMPHOMA - A NEW PARADIGM IN DIAGNOSIS?

ABSTRACT

Background: Recognized as an entity in the 2016 WHO Classification of Tumors of Hematopoietic and Lymphoid Tissues, Pediatric-Type Follicular Lymphoma (PTFL) is a rare nodular follicular lymphoma that affects primarily children and young adults. The clinical presentation is characterized by the sudden appearance of an isolated lymphadenopathy, with a predilection for the head and neck region, without systemic symptoms. The incidence is higher in men. It has an excellent prognosis with the excision of the affected ganglion. By definition, diagnosis is histological, immunocytochemical and molecular. There are no known risk factors or any described association with immunodeficiency or viral infections. Aims: We report two clinical cases. Methods: Case 1 - a previously healthy 18-year-old boy with an isolated, non-painful, cervical lymphadenopathy of approximately 20 mm, which was incidentally found. Case 2 - a 13-year-old boy without relevant personal history, who, after the second dose of vaccination against COVID-19, developed multiple adenomegalies that spontaneously regressed. However, one month later, a right submandibular adenomegaly appeared. It was analysed by ultrasound and was described as suspicious. In both cases, a fine-needle lymph node biopsy was performed for cytological diagnosis and material was sent for immunophenotyping by flow cytometry and molecular cytogenetics by FISH. Results: Immunophenotyping suggested a large-cell B-lymphoma with a phenotype compatible with Burkitt's Lymphoma (BL). In the cytology of both cases, the population observed was more consistent with diffuse large B cell lymphoma (DLBCL) or possibly high-grade follicular lymphoma (FL). In the FISH study, no rearrangements in the MYC, BCL2, BCL6 or IRF4 genes were detected in the samples of the two cases. The lymphadenopathies were excised with a probable diagnosis of PTFL or DLBCL. Histological examination confirmed the PTFL diagnosis. Summary/Conclusion: We did not find in the literature any reference to clear causal relationship between vaccination against COVID-19 and the onset of lymphoproliferative diseases. The cytological/immunophenotypic/molecular approach of this entity in both cases seems to define a characteristic pattern, which may eventually allow, in a first approach, to suspect this diagnosis. More extensive studies will be needed to establish the role of these methodologies in the diagnosis of this pathology.