Chromosome 7q31 Amplification in Fluorescence In-Situ Hybridization: A Hallmark of Hepatosplenic Gamma Delta T Cell Lymphoma

Excerpt

A 16-year-female presented with history of irregular fever of five-month duration and left upper quadrant pain. She had moderate pallor, mild hepatomegaly and massive splenomegaly. Hemogram showed pancytopenia (hemoglobin-71 gm/L, total leucocyte count-2.0 × 10⁹/L and platelet count-34 × 10⁹/L). Peripheral blood film showed normal differential leukocyte counts with presence of nucleated red cells. Clinical, bone marrow (Fig. 1a–c), immunophenotypic findings (Fig. 1d–i) and T cell receptor gamma gene re-arrangement assay (Fig. 2a) were consistent with a diagnosis of hepatosplenic T cell lymphoma of gamma-delta T cell receptor type (γδHSTL). Fluorescence in-situ hybridization (FISH) testing showed 5–7 copies of 7q31 and two copies of centromere 7 consistent with amplification of 7q31 locus (Fig. 2b). Patient received 3 cycles of CHOP (Cyclophosphamide, Doxorubicin, Vincristine and Prednisolone) therapy till last follow up. Patient responded well with improvement in symptoms and hemogram findings (hemoglobin-139 g/L, leukocyte count-6.5 × 10⁹/L and platelet count-83.0 × 10⁹/L). Amplification of 7q22-q31 results from either isochromosome 7q [(i7)(q10)] or ring 7 (r7) [1]; and results in not only the gain of several putative cancer genes in 7q22-31 region, but also loss of genes in 7p favouring tumour growth [2]. While, (i7)(q10) and r(7) are hall mark findings identified by karyotyping in γδHSTL, the demonstration of amplification of 7q31 by a dual-colour FISH is an alternative cost-effective method to establish the diagnosis in patients with a diagnostic dilemma with closely related differential diagnoses including T-lineage acute lymphoblastic leukaemia-γδ type.

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