When Lymphoma Strikes the Pancreas: A Rare Presentation of Systemic Anaplastic Lymphoma Kinase-Negative Anaplastic Large Cell Lymphoma in a Human Immunodeficiency Virus-Positive Patient.

Anaplastic lymphoma kinase (ALK)-negative anaplastic large cell lymphoma (ALCL) is an uncommon subtype of non-Hodgkin lymphoma, with pancreatic involvement being exceedingly rare and documented in only a handful of case reports. We present a unique case of a 31-year-old human immunodeficiency virus (HIV)-positive male with multisite ALK-negative ALCL, who initially presented with a buttock ulcer, leading to a suspicion of primary cutaneous ALCL or lymphomatoid papulosis. However, the discovery of multiple extracutaneous sites, including an atypical pancreatic head involvement, confirmed the diagnosis of systemic ALK-negative ALCL with cutaneous manifestation. The patient received six cycles of brentuximab vedotin + cyclophosphamide-doxorubicin-prednisone (BV + CHP) treatment, achieving a substantial reduction in the size of the pancreatic head mass and no detectable fluorodeoxyglucose (FDG) uptake on positron emission tomography (PET) scan. This case underscores the diagnostic challenges of ALK-negative ALCL in HIV-positive patients with extranodal presentations and demonstrates the potential effectiveness of targeted therapeutic strategies for such cases.