title: A small cell variant of ALK-positive, CD8-positive anaplastic large cell lymphoma with primary subcutaneous presentation mimicking subcutaneous panniculitis-like T-cell lymphoma.
abstract: ALK-positive anaplastic large cell lymphoma (ALK+ ALCL) is an uncommon non-Hodgkin's lymphoma of T-cell origin, the majority of which express CD4 and show frequent pan-T-cell antigen loss. While most cases of ALK+ ALCL have the common pattern characterized by anaplastic morphology with hallmark cells, a less common but well-recognized variant with a small cell pattern may pose a diagnostic challenge. We report a case of ALK+ ALCL with small cell morphology and CD8 subset restriction in a 53-year-old male patient who presented primarily with multiple recurrent subcutaneous nodules with histopathologic features simulating a subcutaneous panniculitis-like T-cell lymphoma (SPTCL). The case was initially diagnosed as SPTCL but was reconsidered as ALK+ ALCL when the incidental finding of CD30 positivity on a subsequent biopsy prompted an ALK immunostain, which turned out to be positive in the neoplastic T-cells. The diagnosis of ALK+ ALCL, small cell variant, was then confirmed by detection of an ALK gene rearrangement by FISH analysis. This report highlights a case of ALK+ ALCL with a deceiving clinical and histopathologic presentation, and emphasizes the value of immunohistochemical panel studies and genetic tests in such cases to avoid diagnostic errors.
authors.affiliation: Department of Pathology, Duke University Medical Center, Durham, NC 27710, United States. endi.wang@duke.edu
authors.forename: Endi
authors.initials: E
authors.lastname: Wang
authors.forename: John
authors.initials: J
authors.lastname: Papalas
authors.forename: Imran
authors.initials: I
authors.lastname: Siddiqi
authors.forename: Maggie
authors.initials: M
authors.lastname: Stoecker
authors.forename: Catherine
authors.initials: C
authors.lastname: Rehder
authors.forename: Siby
authors.initials: S
authors.lastname: Sebastain
authors.forename: Jim
authors.initials: J
authors.lastname: Burchette
authors.forename: Qin
authors.initials: Q
authors.lastname: Huang
mesh_terms: D000077548:Anaplastic Lymphoma Kinase; D014408:Biomarkers, Tumor / Q000032:analysis; D016827:CD8 Antigens / Q000378:metabolism*; D003937:Diagnosis, Differential; D006801:Humans; D017730:Ki-1 Antigen / Q000378:metabolism; D017728:Lymphoma, Large-Cell, Anaplastic / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D016399:Lymphoma, T-Cell / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D015434:Panniculitis / Q000473:pathology*; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: D014408:Biomarkers, Tumor; D016827:CD8 Antigens; D017730:Ki-1 Antigen; C000626173:ALK protein, human; D000077548:Anaplastic Lymphoma Kinase; D020794:Receptor Protein-Tyrosine Kinases