To present a clinical case of follicular lymphoma (FL) transformed into Burkitt's lymphoma (BL) in a patient with acquired immunodeficiency, a rare case with little description in the literature. Methods: retrospective descriptive work of a clinical case carried out through data collection from HSPE medical records.

Woman, 62 years old, seeks emergency care due to generalized lymph node enlargement, fever, night sweats and weight loss. In the investigation, infection with the acquired immunodeficiency virus (HIV) and pulmonary tuberculosis was detected, and later there was the diagnosis of grade 3B FL, through a biopsy of the cervical lymph node. Positive immunohistochemistry for CD79A, CD20, BCL6 and KI-67 40%; negative for CD10, BCL2 and C-MYC. Treatment with RIPE and ART regimen was started and LF's outpatient follow-up was chosen. On CT scans, patient had stable lymph node enlargement with the largest measuring 2.1x1.6 cm in the left armpit. Seven months after the diagnosis, the patient had headache, arthralgia, abdominal pain and ecchymosis on the lower limbs. Tests showed hemoglobin (Hb) 12.5 g/dL, hematocrit (Ht) 36.6%, leukocytes (Lt) 17360/mm3, atypical lymphocytes and platelets 15000/mm3; lactic dehydrogenase (LDH) 13318 U/L, creatinine (Cr) 1.2 mg/dL, triglycerides 460 mg/dL, ferritin 2260 ng/mL, uric acid 17.8 mg/dL. Myelogram: 91% of small to moderately sized cells, high nucleus/cytoplasm ratio, loose chromatin, barely evident nucleoli and cytoplasm with intense basophilia without granulation and with microvacualization, suggestive of BL. Positive immunophenotyping for CD10, CD13, CD15, CD19, CD20, CD38, CD71, CD79a, CD81, cytoplasmic IgM, HLA-DR, Kappa. FISH with MYC-IGH gene rearrangement. CT with enlarged lymph node enlargement, the largest one in the left axillary 4.7 x 3.8cm. After 24 hours, the LDH was 22142 U/L, Cr 2.9 mg/dL, Hb:7.8 g/dL, Lt 57120/mm3 with 45% blasts and platelets 25000/mm3. Chemotherapy with R-CODOX-M was initiated, but the patient died on the 1st day of chemotherapy. Discussion: The most common histological transformation of LF occurs to a diffuse large B cell. Transformation into BL is uncommon. The subsequent molecular events that lead to transformation into a high-grade lymphoma are not fully understood, but a translocation leading to c-myc overexpression appears to be the trigger for transformation. BL may show c-myc-only abnormalities, association with bcl-2, or other karyotypic changes. In the presented case, we highlight an unusual clinical picture in a FL, with severe thrombocytopenia and increased LDH, without constitutional symptoms and/or visible enlargement of lymph nodes, which led to a spinal cord study and the diagnosis of transformation into BL. In one review with 4 cases, the median time to histologic transformation from follicular lymphoma to Burkitt's lymphoma was 6 to 13 months. In the case described, the patient initially had a FL, negative for BCL2 and C-MYC, which turned into a BL after 7 months of evolution, with the MYC-IGH rearrangement. Conclusion: As this is an uncommon evolution of FL, we emphasize the importance of suspecting transformation into high-grade B lymphomas in the face of unusual alterations in FL, such as severe cytopenias, constitutional symptoms, increased LDH and rapid progression of lymphadenopathy so that the treatment is instituted early.