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follicular lymphoma transformed to B lymphoblastic lymphoma

Friday 28 December 2012

Follicular lymphoma transformed to "double-hit" B lymphoblastic lymphoma

Lymphomas showing both MYC/8q24 rearrangement and IGH@BCL2/t(14;18)(q32;q21), also referred to as "double-hit" or "dual-hit" lymphomas (DHL) are rare B-cell malignancies with a germinal center B-cell immunophenotype and heterogeneous cytologic and histologic features.

Such lymphomas may arise de novo or through transformation of follicular lymphomas and are classified either as "B-cell lymphoma, unclassifiable, with features intermediate between diffuse large B-cell lymphoma (DLBCL) and Burkitt lymphoma (BL)" (most commonly), DLBCL, or, rarely, as B-lymphoblastic lymphoma.

Cytologic examination shows two distinct populations of neoplastic lymphoid cells, a predominant population of larger cells with fine powdery ("blastic") chromatin, visible to prominent nucleoli and occasional small cytoplasmic vacuoles and a less numerous population of smaller cells with centrocytic morphology.

Flow cytometry also shows two distinct monotypic B-cell populations, both expressing CD10, and TdT-positivity was demonstrated immunohistochemically.

Fluorescence in situ hybridization (FISH) demonstrates both MYC rearrangement and IGH/BCL2 gene fusion and cytogenetic analysis showed a complex karyotype including both t(14;18)(q32;q21) and t(8;22)(q24.1;q11.2).

Since DHL pursue an aggressive clinical course, respond poorly to therapy, and have a poor outcome, it is important to suspect the diagnosis when encountering neoplastic lymphoid cells that are difficult to classify in effusion cytology specimens and to order the appropriate immunophenotyping and cytogenetic studies.

Reference

- Follicular lymphoma transformed to "double-hit" B lymphoblastic lymphoma presenting in the peritoneal fluid. Kaplan A, Samad A, Dolan MM, Cioc AM, Holman CJ, Schmechel SC, Pambuccian SE. Diagn Cytopathol. 2012 May 24. PMID: #22623514#