More than 2 dozen other genes have been reported to be mutated in rare cases of PTFL but in general the genetic abnormalities found in this disorder are fewer and less complex than those in other types of FL. PTFL has an indolent, relapsing and remitting course with a 5-year survival rate of >95%. Patients diagnosed with PTFL have been treated with chemotherapy, surgery, and combinations of these treatments. In general, these patients did well (100% survival with <5% of cases relapsing regardless of treatment modality). More recently, 36 patients have been treated with surgical resection alone followed by observation; all these patients survived with only one having a relapse. Thus, PTFL appears to be a highly indolent type of FL in which multiple studies have reported overall and progression-free survival rates of 100% and >90%, respectively, for >2 years and an estimated probability of 5-year event-free survival rate of ~96%. The therapeutic regimens versus follow-up observations that best treat this disorder in children, adolescents, and adults (adults may require different treatments than children and adolescents) requires further study. Primary follicular lymphoma of the testis
Primary follicular lymphoma of the testis (PFLT), also termed testicular follicular lymphoma, was classified as a distinct form of FL by the World Health Organization in 2016. It is an extremely rare disease that has been recognized as occurring primarily in children and adolescents but also has been reported in 5 adults.
deletions in the q arm of chromosome 1 at position 36, [60-70% of cases]) that lead to lose of TNFAIP3 (encodes tumor necrosis factor, alpha-induced protein 3 which inhibits the activation of NF-κB, blocks cell death due to apoptosis, and regulates lymphocyte-based immune responses through its ubiquitin ligase activity); 3) mutations in PRDM1 (encodes the PR domain zinc finger protein which promotes the maturation and proliferation of B-cells); and 4) the same mutations seen in ISFL including KMT2D (85-90% of cases), CREEBP (40-65% of cases), BCL2 (40-65% of cases), and EZH2 (20-30% of cases) as well as other mutations such as those in the histone-modifying gene HIST1H1E (20-30% of cases), the RRAGC gene (~17% of cases) which regulates cell growth, survival, death, and proliferation, and, in ≤15% of cases several other genes including MEF2B, STAT6, EP300, ARID1A, SLC22A2, CARD11, FOXO1, GNA12, B2M (i.e. the gene for beta-2 microglobulin), and SGK1. Except for the t(14:18)(q32:q21.3) translocation and EZH2 mutations which lead to gains in the expression and function, respectively, of their products, the genetic alterations generally lead to a loss in the production or function of the cited genes products. However, the exact roles, if any, of these genomic abnormalities in promoting the progression of ISFL to FL are unclear.