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Malignant lymphoma, lymphocytic, nodular, NOS [OBS]
Malignant lymphoma, nodular, NOS [OBS]
Other extranodal follicular lymphoma
Pediatric follicular lymphoma
Primary intestinal follicular lymphoma
B-cell malignancy of follicle center cells with at least partial follicular growth pattern, centrocyte (small cleaved cell) predominant with centroblasts (large non-cleaved cells) in minority. Neoplastic follicles closely packed and effacing nodal architecture, neoplastic cells with varying sclerosis between follicles.
Follicular lymphoma, NOS histology is a generic disease description. DCO cases or path report only cases usually stay in this classification. The NOS histology may be the working diagnosis. Further review of the medical record should be done to look for the tests listed as definitive diagnosis. The more specific diagnoses are: follicular lymphoma, grade 1; follicular lymphoma, grade 2, and follicular lymphoma, grade 3. When a more specific diagnosis is identified, the histology should be changed to the more specific neoplasm name and code.
Follicular lymphoma (FL) predominantly involves lymph nodes, but also spleen, bone marrow (BM), peripheral blood (PB) and Waldeyer ring. Less commonly, FL may involve non-hematopoietic extranodal sites such as gastrointestinal tract or soft issue; this usually occurs in a setting of widespread nodal disease. FL may occasionally be primary in extranodal sites including skin, GI tract, particularly the duodenum, occular adnexa, breast, and testis. Most patients present with widespread disease, including peripheral and central (abdominal and thoracic) lymphadenopathy and splenomegaly. The BM is involved in 40-70%. Only 1/3 of patients present with stage I or II at the time of diagnosis. FL has been graded according to the proportion of large cells (centroblasts). Studies suggest this histologic grading predicts clinical outcome, with more large cells behaving more aggressively and having a higher likelihood of progression to diffuse large cell lymphoma. When any area of diffuse large-B-cell lymphoma (DLBCL) is present in a FL the disease should be reported as diffuse large B-cell lymphoma (See PH rules).
There are three variants of FL: pediatric follicular lymphoma, primary intestinal follicular lymphoma, and other extranodal follicular lymphomas.
Pediatric follicular lymphoma involves cervical lymph nodes, other peripheral lymph nodes, or Waldeyer ring. Other extranodal involvement may occur. Children with FL typically have early stage disease. Pediatric FL lymphoma typically lacks BCL2 protein expression and t(14;15). Most are grade 3.
Primary intestinal follicular lymphoma in the GI tract occurs most commonly in the small intestine, and frequently involves the duodenum. Duodenal follicular lymphoma is predominantly found in the second portion of the duodenum, presenting as multiple polyps. The diagnosis is most often an incidental finding. Most patients have localized disease and prognosis is excellent even without treatment.
Other extranodal follicular lymphomas occur in almost any extranodal site. Patients usually have localized extranodal disease and systemic relapses are rare. Testicular follicular FL are reported with increased frequency in children, but also are reported in adults.
Definitive Diagnostic Methods
Histological confirmation (with or without)
BCL2 gene rearrangements
Heavy and light chains rearranged; t(14;18)(q32:q21)-85% with rearrangement of Bcl-2 gene