del(2)(p23): a new recurrent abnormality in acute myeloid leukemia

del(2)(p23) as a sole abnormality in a case of acute myeloid leukemia

We report a case of acute myeloid leukemia (AML) [FAB-M5a] showing a deletion of the short arm of chromosome 2 at band p23 as a sole abnormality in the bone marrow cells. This abnormality deserves to be considered as an established nonrandom entity in AML.

Pathobiology of NPM-ALK and variant fusion genes in anaplastic large cell lymphoma and other lymphomas

Despite its clinical and histological heterogeneity, anaplastic large cell lymphoma (ALCL) is now a well-recognized clinicopathological entity accounting for 2% of all adult non-Hodgkin's lymphomas (NHL) and about 13% of pediatric NHL. Immunophenotypically, ALCL are of T cell (predominantly) or Null cell type; by definition, cases expressing B cell antigens are officially not included in this entity. The translocation (2;5)(p23;q35) is a recurring abnormality in ALCL; 46% of the ALCL patients bear this signature translocation. This translocation creates a fusion gene composed of nucleophosmin (NPM) and a novel receptor tyrosine kinase gene, named anaplastic lymphoma kinase (ALK). The NPM-ALK chimeric gene encodes a constitutively activated tyrosine kinase that has been shown to be a potent oncogene. The exact pathogenetic mechanisms leading to lymphomagenesis remain elusive; however, the synopsis of evidence obtained to date provides an outline of likely scenarios. Several t(2;5) variants have been described; in some instances, the breakpoints have been cloned and the genes forming a new fusion gene with ALK have been identified: ATIC-ALK, TFG-ALK and TPM3-ALK. Cloning the translocation breakpoint and identifying the ALK and NPM genes provided tools for screening material from patients with ALCL using various approaches at the chromosome, DNA, RNA, or protein level: positive signals in the reverse transcriptase-polymerase chain reaction (RT-PCR) and the immunostaining with anti-ALK monoclonal antibodies (McAb) serve as the most convenient tests for detection of the t(2;5) NPM-ALK since the fusion gene and ALK protein expression do not occur in normal or reactive lymphoid tissue. The wide range of NPM-ALK positivity reported in different series appears to be dependent on the inclusion and selection criteria of the ALCL cases studied. Overall, however, 43% of ALCL cases were NPM-ALK+ (83% of pediatric ALCL vs 31% of adult ALCL). Occasional non-ALCL B cell lymphomas (4%) with diffuse large cell and immunoblastic histology and Hodgkin's disease cases (3%) were NPM-ALK-, but these data are questionable. The aggregate results indicate that, in contrast to primary nodal (systemic) ALCL, the t(2;5) may be present in only 10-20% of primary cutaneous ALCL and rarely, if at all, in lymphomatoid papulosis, a potential precursor lesion; however, these 10-20% positive cases were not confirmed by anti-ALK McAb immunostaining and may represent an overestimate. Positivity for NPM-ALK is associated to various degrees with the following parameters: 44% and 45% of ALCL cases with T cell and Null cell immunophenotype, respectively, are positive, whereas only 8% of cases with a B cell immunoprofile are positive; the mean age of positive patients is significantly younger than that of negative patients; positive cases carry a better overall prognosis (but not in all studies). Recently, the homogenous category of ALK lymphoma ('ALKoma') has emerged as a distinct pathological entity within the heterogenous group of ALCL. The fact that patients with ALK lymphomas experience significantly better overall survival than ALK- ALCL demonstrates further that analysis of ALK expression has important prognostic implications. The term ALK lymphoma signifies a switch in the use of the diagnostic criteria: cases are selected on the basis of a genetic abnormality (the ALK rearrangement), instead of the review of morphological or immunophenotypical features which are clearly more prone to disagreement and controversy. Since its initial description in 1985 ALCL has become one of the best characterized lymphoma entities.

Acute myeloid leukemia in patients more than 50 years of age: special considerations in diagnosis, treatment, and prognosis

Although most patients with acute myeloid leukemia are more than 50 years of age and age is known to be an adverse prognostic factor, relatively few studies have been conducted to determine the optimum treatment strategy for the older patient. This report suggests that, until definitive studies are conducted in this age group, intensive chemotherapy should always be considered if the older patient's overall status and desires are consistent with this approach. Other factors, specifically cytogenetic and cell-surface marker findings, provide prognostic information, independent of age, and should also be considered during patient management.

Deletion(2)(p23) abnormality in a case of secondary acute myeloid leukemia

We report a case of acute myeloid leukemia (M5a of the FAB classification), secondary to the myelodysplastic syndrome, showing a deletion of the short arm of chromosome 2 at p23 in the bone marrow cells. In addition, a duplication of chromosome 13,dup(13)(q12q14) was found.

del(2)(p23): a consistent recurrent abnormality in acute myelogenous leukemia

A case of acute myelogenous leukemia (AML-M2) with an unusual chromosomal finding is presented. In addition to the most frequently observed translocation in this neoplasia, involving the long arms of chromosomes 8 and 21, there was a partial deletion of the short arm of chromosome 2 band (p23), i.e., 46,XX,del(2)(p23),t(8;21)(q22;q22). Deletion of the short arm of chromosome 2 has been described in association with other chromosome abnormalities in two other cases of AML and as the sole abnormality in three cases of AML, indicating that this abnormality is nonrandom and may be associated with leukemic transformation of hematopoietic cells. Therefore, we propose that the del(2)(p23),t(8;21)(q22;q22) abnormality be accorded status III and possibly considered a subset of AML (M2).