KSHV/HHV-8 associated lymph node based lymphomas in HIV seronegative subjects. Case report and review of the literature

Extracavitary primary effusion lymphoma (ExPEL) is a rare, high-grade lymphoproliferative disorder that displays immunoblastic, plasmablastic, or anaplastic morphology. It usually lacks expression of B-cell and T-cell markers, but often expresses the plasma cell markers CD138 and MUM1, and the activation marker CD30, along with EMA. ExPEL, similar to classic PEL occurring as lymphomatous effusions in serous body cavities without an associated tumor mass, is consistently associated with human herpes virus-8 (HHV8) infection, while a majority of cases also exhibits Epstein–Barr virus (EBV) co-infection. Clinically, it is characterized by an almost exclusive male predominance (98% male), HIV-positivity (96% of patients are HIV +), acute presentation with B symptoms, and unfavorable overall survival (40% of patients die within 2 months). We report an asymptomatic HIV-negative female patient with incidentally found splenomegaly and extensive PET FDG-avid retroperitoneal, pelvic, and mediastinal lymphadenopathy. A core biopsy of her right pelvic lymph node showed aggregates of atypical cells with anaplastic features. Immunohistochemistry revealed that the neoplastic cells were positive for CD45, CD20, CD30, MUM1, CD138, EMA, CD3, HHV-8 and EBER. The diagnosis of ExPEL was established. Against medical advice and given the absence of significant symptoms, the patient refused to start treatment. Four months after the diagnosis, the patient remains asymptomatic, and follow-up CT scan demonstrates stability of her lymphadenopathy. We present here a case of ExPEL in which the patient's presentation defies the clinical norms, illustrating that ExPEL should also be included in the differential diagnosis of lymphomas occurring in asymptomatic HIV-negative patients.