A 30-year-old man comes to the emergency department due to rapidly increasing abdominal distention and anorexia. The patient has a history of HIV infection and intravenous drug use. CT scan of the abdomen shows ascites and a large mass involving the small intestine. Biopsy of the mass reveals sheets of uniform, round, medium-sized tumor cells with basophilic cytoplasm and a very high rate of proliferation and apoptosis. Which of the following infectious agents is most closely associated with the development of this patient's condition?
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This patient with rapidly increasing abdominal distention and abdominal mass has histopathology consistent with Burkitt lymphoma (BL), an aggressive B-cell malignancy. Epstein-Barr virus (EBV) is the infectious agent most strongly associated with BL pathogenesis.
EBV infects B cells via the CD21 complement receptor. Infected cells produce viral proteins that stimulate signaling pathways (eg, JAK/STAT), triggering proliferation. This proliferation of infected B cells is usually limited by T cells, but some B cells may reduce production of EBV antigens and escape recognition. An impaired immune response (eg, HIV, persistent malaria) can also enable continuous B-cell division. Proliferating B cells are more likely to acquire genetic abnormalities (eg, chromosomal translocations), resulting in a neoplastic clone. BL cells harbor the translocation t(8;14), which causes MYC overexpression, uncontrolled cell growth, and rapid enlargement.
Nonendemic BL often involves the gastrointestinal tract, which can present as an enlarging abdominal mass with ascites (due to lymph obstruction) and distention. Histopathology shows uniform, medium-sized lymphoid cells with basophilic cytoplasm and numerous mitotic figures (indicating high proliferation rate) and apoptotic bodies. Scattered macrophages, which digest the apoptotic debris, produce the characteristic "starry sky" appearance.
(Choice B) Helicobacter pylori is associated with gastric lymphoma (eg, marginal zone lymphoma of mucosa-associated lymphoid tissue [ie, MALT lymphoma]). Gastrointestinal MALT lymphomas may cause abdominal discomfort but are typically indolent and slow growing (ie, would have lower proliferation rate). Rapid abdominal distention would be unusual.
(Choice C) Chronic hepatitis B can cause hepatocellular carcinoma. Although patients may have abdominal distention and ascites, imaging would reveal a liver mass, not an intestinal lesion. Histopathology often shows thickened plates of malignant hepatocytes (eg, polygonal cells, eosinophilic cytoplasm).
(Choice D) Human herpesvirus 8 can cause Kaposi sarcoma (KS), a vascular tumor seen in HIV-positive individuals. Although it can involve the gastrointestinal tract in later stages, KS typically presents initially with cutaneous lesions. Histopathology often shows spindle-shaped endothelial cells and slit-like vascular spaces.
(Choice E) High-risk human papillomavirus types (eg, 16, 18) have been identified in cervical squamous cell carcinoma. Histopathology often shows invasive nests of malignant cells with squamous differentiation (eg, intercellular bridges).
Educational objective:
Burkitt lymphoma, an aggressive B-cell malignancy, can be associated with Epstein-Barr virus infection. It typically presents as a rapidly growing mass (eg, abdomen). Histopathology shows sheets of uniform, medium-sized lymphoid cells with numerous mitotic figures (ie, high proliferation rate) and apoptotic bodies.