Striking morphology of leukemic phase of childhood peripheral T‐cell lymphoma, not otherwise specified
Authors: Anita Chopra, Rajive Kumar, Rachna Seth, Mona Anand, Ruma Ray
Journal: American Journal of Hematology (2010)

Leukemic phase of childhood peripheral T-cell lymphoma, not otherwise specified is rare [1] and is even more uncommon in children. The purpose of this communication is to record the very striking morphology of this entity that we saw in a 7-year-old child who presented with fever, features of superior mediastinal syndrome, lymphadenopathy, and enlarged liver (8 cm) and spleen (14 cm). Total leukocyte count was 70 × 103/μl, hemoglobin 9.6 g/dl, and platelets 23.2 × 103/μl. Total serum bilirubin was elevated (8.9 mg/dl; conjugated 6.9 mg/dl), SGOT/SGPT were 208/109 IU/L, alkaline phosphatase was 1,132 IU/L, and there was a reversal of albumin:globulin ratio. Monospot test for infectious mononucleosis was also negative. Peripheral blood examination showed two populations of cells ( Images 1 and 2). The preponderant population was of small, morphologically mature, atypical lymphoid cells that had nuclei with irregular outline and often deep clefts. A small but significant population of large cells of heterogeneous morphology was also present. These had moderate to abundant deep blue cytoplasm with vacuoles in some. Nuclei were generally round to oval but were irregular in some. Prominent to ill-defined single nucleolus was present in a few of these. Mitotic figures were present. Myeloperoxidase cytochemistry was negative. Peripheral blood smear showing presence of small and large morphologically mature atypical lymphoid cells. Clefts in the nuclei of small cells are clearly evident and large cells are of heterogenous morphology (Jenner & Giemsa, 100×). Photomicrographs of representative cells from different fields showing details of their morphology (Jenner & Giemsa, 100×). Cervical lymph node biopsy ( Image 3) showed a total effacement of lymph nodal architecture by small to intermediate-sized lymphoid cells having vesicular nuclei of irregular contour with prominent to inconspicuous nucleoli. There was a prominence of high endothelial venules. The background cells were comprised of inflammatory cells including small lymphocytes, eosinophils, and histiocytes. Leukocyte common antigen and CD3 were positive on immunohistochemistry, and CD20, CD30, and ALK were negative. Flow cytometric analysis of peripheral blood showed the lymphoid cells to be positive for CD3, CD5dim, CD7dim, and CD8 (heterogeneous), negative for TdT, CD34, CD117, CD13, CD33, CD14, CD10, CD19, CD22, and CD4. Based on the above findings, a diagnosis of PTCL not otherwise specified (PTCL, NOS) was given. Lymph node biopsy showed a total effacement of nodal architecture by small to intermediate-sized lymphoid cells having vesicular nuclei of irregular contour with prominent to inconspicuous nucleoli (Hemotoxylin & Eosin, 40×). The child was treated with steroids for superior mediastinal syndrome but steadily deteriorated. Total leukocyte count increased to >100 × 103/μl, liver function progressively worsened, and the child succumbed to disseminated intravascular coagulopathy, fulminant sepsis, hepatic encephalopathy, and massive pulmonary bleed. The key observation that made diagnosis possible was the complete dissimilarity of cells with any leukemia that one sees in children, combined with results of immunophenotypic analysis. The small irregular cells which predominated were morphologically mature and clearly lymphoid. What lent further uniqueness to the picture was the presence of a much smaller but significant number of very large cells of heterogeneous appearance. The identity of the leukemic cells was established by immunophenotyping which showed a mature T-cell phenotype. The immunophenotypic results with CD5, CD7, CD4, and CD8 were overall consistent with PTCL [2]. In a case such as ours, NK cell lymphoblastic leukemia/lymphoma and precursor T-ALL may also be considered. However, the fact that surface CD3 (not cytoplasmic CD3 alone) was positive should support the diagnosis of PTCL, NOS, and not NK cell lymphoblastic leukemia/lymphoma. Moreover, CD4 is often positive in NK cell lymphoblastic leukemia/lymphoma [3], but in our case, it was negative. Similarly, we could rule out precursor T-ALL on the basis of mature and distinctive morphology and negativity of CD34 and TdT. An unfamiliar leukemic blood picture comprised predominantly of morphologically mature lymphoid cells of irregular nuclear outline analogous to nuclear convolutions seen on lymph node biopsy, with a significant sprinkling of very large bizarre cells is the best clue that should lead one to suspect and investigate leukemic phase of PTCL in children.