Lymphoblastic leukemia with surface light chain restriction: A diagnostic dilemma.

Surface light chain expression is a feature of mature B‑cell neoplasms. Light chain restriction in precursor B acute lymphoblastic leukemia is infrequently seen. We report a case of a 28‑year‑old female with non‑FAB L3 morphology blasts and immunophenotypic features showing overlap between a precursor and mature B‑cell neoplasm.

‘Childhood systemic mastocytosis associated with t (8; 21) (q22; q22) acute myeloid leukemia’.

Systemic mastocytosis (SM) with associated clonal nonmast cell lineage disease is seen in up to 20% cases of SM. SM is uncommon in the pediatric population. T (8; 21) (q22; q22) is a good prognostic factor in acute myeloid leukemia (AML). However, the presence of SM confers poor prognosis in t (8; 21) (q22; q22) associated AML. We report the case of a child with t (8; 21) (q22; q22) associated AML with SM and her minimal residual disease status over the course of her treatment. In our case, the abnormal mast cells, showing co‑expression of CD25 and CD2, persisted even after the marrow showed no evidence of residual AML.

Blastic plasmacytoid dendritic cell neoplasm: Report of two pediatric cases.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare subtype of acute leukemia that typically follows a highly aggressive clinical course in adults, whereas experience in children with this disease is very limited. We report cases of two children in whom bone marrow showed infi ltration by large atypical monocytoid ‘blast-like’ cells which on immunophenotyping expressed CD4, CD56, HLA-DR and CD33 while were negative for CD34 other T-cell, B-cell and myeloid markers. The differential diagnoses considered were AML, T/NKcell leukemia and acute undifferentiated leukemia. Additional markers CD303/ BDCA-2 and CD123 which are recently validated plasmacytoid dendritic cell markers were done which helped us clinch the diagnosis of this rare neoplasm. An accurate diagnosis of BPDCN is essential in order to provide prompt treatment. Due to its rarity and only recent recognition as a distinct clinicopathological entity, no standardized therapeutic approach has been established for BPDCN.

Characterization of cryptic rearrangements, deletion, complex variants of PML, RARA in acute promyelocytic leukemia.

Acute promyelocytic leukemia (APL) is characterized by a reciprocal translocation t(15;17)(q22;q21) leading to the disruption of Promyelocytic leukemia (PML) and Retionic Acid Receptor Alpha (RARA) followed by reciprocal PML–RARA fusion in 90% of the cases. Fluorescence in situ hybridization (FISH) has overcome the hurdles of unavailability of abnormal and/or lack of metaphase cells, and detection of cryptic, submicroscopic rearrangements. In the present study, besides diagnostic approach we sought to analyze these cases for identification and characterization of cryptic rearrangements, deletion variants and unknown RARA translocation variants by application of D-FISH and RARA break-apart probe strategy on interphase and metaphase cells in a large series of 200 cases of APL. Forty cases (20%) had atypical PML–RARA and/or RARA variants. D-FISH with PML/RARA probe helped identification of RARA insertion to PML. By application of D-FISH on metaphase cells, we documented that translocation of 15 to 17 leads to 17q deletion which results in loss of reciprocal fusion and/or residual RARA on der(17). Among the complex variants of t(15;17), PML–RARA fusion followed by residual RARA insertion closed to PML–RARA on der(15) was unique and unusual. FISH with break-apart RARA probe on metaphase cells was found to be a very efficient strategy to detect unknown RARA variant translocations like t(11;17)(q23;q21), t(11;17)(q13;q21) and t(2;17)(p21;q21). These findings proved that D-FISH and break-apart probe strategy has potential to detect primary as well as secondary additional aberrations of PML, RARA and other additional loci. The long-term clinical follow-up is essential to evaluate the clinical importance of these findings.