Abstract
ALK-negative anaplastic large cell lymphoma (ALCL, ALK－) is a CD30+ T-cell neoplasm composed of large lymphoid cells with abundant cytoplasm and pleomorphic nuclei that lacks expression of ALK protein. We describe a case of ALCL, ALK－with primary involvement of the rectum in a 37 year old man, where the original diagnosis was established based on a colonoscopic biopsy. T-cell lymphomas are rare in the colorectal area and besides ALCL, their differential diagnosis includes enteropathic T-cell lymphoma, peripheral T-cell lymphoma, not otherwise specified, NK/T cell lymphoma, or NK-cell enteropathy. In addition, syncytial variant of classical Hodgkin lymphoma or a pleomorphic CD30-positive diffuse large B-cell lymphoma should also be ruled out. We discuss pitfalls of the differential diagnosis and review the literature of anaplastic large cell lymphoma in the gastrointestinal tract. Correct diagnosis of ALCL in the colon is important to avoid a colorectal surgery for an assumed adenocarcinoma, and to open the possibility for lymphoma-directed chemotherapy.
Highlights
Anaplastic large cell lymphoma (ALCL) is a CD30positive neoplasm of T-cell or null-cell lineage with characteristic clinicopathologic features, and accounts for 3% of all adult non-Hodgkin lymphomas (NHL)
We describe a unique case of anaplastic lymphoma kinase (ALK)− ALCL presenting as an incidental small rectal ulcer
ALCL, ALK− is included as a provisional entity in the World Health Organization (WHO) classification, and is defined as a CD30+ T-cell neoplasm that is not reproducibly distinguishable on morphological grounds from ALCL, ALK+, but lacks ALK protein
Summary
Anaplastic large cell lymphoma (ALCL) is a CD30positive neoplasm of T-cell or null-cell lineage with characteristic clinicopathologic features, and accounts for 3% of all adult non-Hodgkin lymphomas (NHL). Two subsets of systemic ALCL are currently recognized in the World Health Organization (WHO) classification. One subset expresses the oncogenic protein anaplastic lymphoma kinase (ALK) as a result of either t (2;5) (p23; q35) translocation or variant alk rearrangement. The second subset includes ALK-negative (ALK−) tumors that cannot be distinguished from ALCL, ALK-positive (ALK+) based on morphological features and express CD30 [1]. The provisional ALK− ALCL category was formed to reflect distinguishing clinical data, including the advanced median age and more aggressive clinical course of cases of ALK-negative ALCL. We describe a unique case of ALK− ALCL presenting as an incidental small rectal ulcer
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