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.
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.
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.
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.
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.
Abnormalities of chromosome 2p23 with expression of ALK1 and p80 occur in both inflammatory myofibroblastic tumor (IMT) and anaplastic large cell lymphoma.
Histology, immunohistochemistry, and T-cell gene rearrangement studies were supportive of a CD 30-positive ALK-1 negative anaplastic large cell lymphoma.
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.
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.
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.