The tumor cells were positive for CD30, CD4, and CD43, negative for CD20, CD3, ALK-1 and Epstein-Barr virus (EBV)-encoded small RNAs (EBERs) in situ hybridization, establishing the diagnosis of primary gastric ALK-negative ALCL.
Here, we report a case of primary pulmonary ALK-1 positive ALCL which was initially recognized in bronchial brushing cytology based on distinct morphologic clues.
In an analysis of 25 previously reported primary CNS ALCLs, ALK-1 positivity was shown to be prevalent in younger age, as ALCL occurs outside the brain.
9p24 gains were detected in 6/17 (35%) primary mediastinal B-cell lymphomas (PMBCLs), 25/77 (33%) Hodgkin's lymphomas (HLs), 3/16 (19%) angioimmunoblastic T-cell lymphomas (AILTs) and 1/5 ALK1(+) anaplastic large cell lymphomas (ALCLs); breaks were observed only in three cases. pJAK2 expression was most prevalent in PMBCL, peripheral T-cell lymphomas and HL. pSTAT3 predominated in ALCLs, HLs, AILTs, PMBCLs and peripheral T-cell lymphomas. pSTAT5 expression was detected frequently in follicular lymphomas, diffuse large B-cell lymphomas and AILTs.
Histology, immunohistochemistry, and T-cell gene rearrangement studies were supportive of a CD 30-positive ALK-1 negative anaplastic large cell lymphoma.
Abnormalities of chromosome 2p23 with expression of ALK1 and p80 occur in both inflammatory myofibroblastic tumor (IMT) and anaplastic large cell lymphoma.
However, CD13 positivity has not previously been described in a case of CD30+ (ALK-1+) anaplastic large-cell lymphoma of presumed null-cell origin without histiocytic differentiation.
We conclude that immunohistochemical studies, using antibody ALK1. and FISH for ALK gene rearrangement are equally effective for identifying patients with ALCL who have a favorable clinical outcome.
The diagnosis of ALCL was based on immuno-morphological features and all the cases but 2 were investigated using ALK1 antibody directed to the NPM/ALK protein associated with the 2;5 translocation.
The t(2;5)(p23;q35) translocation, associated with anaplastic large-cell lymphoma (ALCL), results in the expression of a chimeric NPM-ALK protein that can be detected by the ALK1 monoclonal antibody.
In summary, immunohistochemistry with ALK1 antibody allows the identification of a distinct subgroup within the ALCL of T or null phenotype that is associated with 2p23 abnormalities and lacks the marked histological pleomorphism described in ALCL in general.