Abstract
Adult T-cell leukemia/lymphoma (ATLL) is a rare, human T-lymphotropic virus type 1 (HTLV-1)–driven neoplasm that is often underrecognized in low-endemic regions. We describe a 23-year-old man with an eight-year history of chronic dry cough who later developed weight loss, night sweats, odynophagia, and dyspnea. CT revealed cervical/supraclavicular lymphadenopathy with innumerable pulmonary micronodules, interlobular septal thickening, and ground-glass opacities; abdominal imaging showed hepatosplenomegaly, ascites, and extensive retroperitoneal/mesenteric adenopathy. HTLV-1 ELISA and confirmatory Western blot were positive. Excisional lymph node biopsy demonstrated diffuse architectural effacement by atypical T cells with a CD3+, CD4+, CD5+, CD25+, CD7–, granzyme B+ immunophenotype and a ~90% Ki-67 index, establishing lymphomatous-type ATLL with a cytotoxic profile. Despite rapid recognition, the patient deteriorated and died from respiratory failure 15 days after diagnosis, before chemotherapy could begin. This lung-predominant presentation in a young adult illustrates how ATLL can mimic chronic pulmonary disease and evade early detection outside endemic areas. Clinicians should prioritize early tissue acquisition and a minimal T-cell panel (CD3, CD4, CD25, CD7, Ki-67); a CD4+CD25+ phenotype with CD7 loss should prompt HTLV-1 testing irrespective of geography. Streamlined access to immunophenotyping and confirmatory HTLV-1 assays is essential to reduce diagnostic delays and improve outcomes.