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Malignant lymphoma, small cleaved cell, follicular [OBS]
A neoplasm of follicle centre B cells (centrocytes/cleaved follicle centre cells (FCC) and centroblasts/noncleaved FCC) which has at least a partially follicular pattern 0-5 centroblasts/hpf
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).
FL grade 1 may subsequently be diagnosed with a grade 2 or grade 3 FL. This is not a new primary, it is noting that there are more centroblasts in the BM and the disease is more aggressive.
There are three variants of FL: Pediatric FL, primary intestinal FL, and other extranodal FL.
Pediatric FL involves cervical lymph nodes, other peripheral lymph nodes, or Waldeyer ring, however other extranodal involvement occurs. 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 FL in the GI tract occurs most commonly in the small intestine, and frequently involves the duodenum. Duodenal FL is predominantly found in the second portion of the duodenum, presenting as multiple polyps. The diagnosis is Most often as 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 FL are reported with increased frequency in children, but also are reported in adults.
Code follicular lymphoma, grade 2, when there is a grade such as 1-2. Take the higher grade, even though the grade 1 histology code is higher.
Definitive Diagnostic Methods
Histologic confirmation (with or without)
BCL2 gene rearrangements
Chromosomal translocations T(11;18)
IGH(VD-J) gene rearrangement
Immunoglobin heavy and light chain genes rearranged
Heavy and light chains rearranged; t(14;18)(q32:q21)-85% with rearrangement of Bcl-2 gene