Lymphoblastic Transformation of Follicular Lymphoma: A Case Report and Review of the Literature

Follicular lymphoma (FL) is one of the most common B-cell non-Hodgkin lymphomas in adults in the Western world. Prognosis is correlated with the clinical stage and histologic grade and, increasingly, the tumor genetic profile. A subset of patients with FL experiences histologic disease progression (ie, histologic transformation), of which the majority will demonstrate diffuse large B-cell lymphoma. We describe a patient initially diagnosed with low-grade FL with relapsed disease presenting as acute renal failure due to diffuse abdominal lymphadenopathy. Excisional biopsy of an inguinal lymph node at relapse showed high-grade areas with sheets of immature-appearing lymphoid cells adjacent to nodular areas characteristic of low-grade FL. Cells of both components were positive for BCL2 and CD19. The cells of the high-grade component were positive for CD99 and TdT and negative for CD20, whereas cells of the low-grade component were positive for CD20 and negative for CD99 and TdT. Fluorescence in situ hybridization studies demonstrated the IGH/BCL2 rearrangement in addition to an MYC rearrangement in both low- and high-grade components.