PTFL occurs in male (male to female ratio ~10;1) children or adolescents (ages 1–17 years, median age ~13-14), less frequently in young adults (ages 18–30 years), and occasionally in older adults. In ~90% of cases, the diseases is diagnosed in an early stage (i.e. stage I or II) and localized to one or two adjacent lymph node chains. Historically, PTFL has been described as commonly presenting with swollen lymph nodes and/or tonsils in the head and neck regions, less commonly as swollen lymph nodes in the axillary and/or inguinal regions, and/or rarely as swollen lymph nodes in the abdomen and/or infiltrations of the malignant cells into the testes, bone marrow, and/or central nervous system. However, many if not all of the latter rare cases as well as cases that exhibit tonsil involvement are now regarded by the World Health Organization (2016) as due to a provisional entity termed large B-cell lymphoma with IRF4 rearrangement. This diseases is a follicular-type large B-cell lymphoma that also afflicts children, adolescents, and young adults but is otherwise distinguished from PTFL by its lack of a strong predominance in males, its common occurrence in extra-nodal sites, its histology, its clinical course, and the genomic alterations carried by its malignant B-cells, particularly the hallmark translocation of the IRF4 (interferon regulatory factor 4) gene (also termed the MUM1 or melanoma associated antigen (mutated) 1 gene) on the short (i.e. p) arm of chromosome 6 at position 25.3 near to the IGH@ immunoglobulin heavy locus on the long (i.e. q) arm of chromosome 14 at position 32.33 This acquired genomic abnormality forces the overexpression of interferon regulatory factor protein. Excluding cases now regarded as being large B-cell lymphomas with IRF4 rearrangement, PTFL presents almost exclusively with enlargement of lymph nodes in the head, neck, axilla, or groin.
Pediatric-type follicular lymphoma
Nodal marginal zone B cell lymphoma
Duodenal-type follicular lymphoma
Marginal zone B-cell lymphoma
Nodular lymphocyte predominant Hodgkin lymphoma
Follicular lymphoma
Indolent lymphoma
AIDS-related lymphoma