32-year-old Nigerian woman, who had recently immigrated to the USA, presented to the emergency department complaining of cramplike abdominal pain for 1 week. Examination revealed oral thrush and a palpable abdominal mass. Radiographic studies are shown below (Figures 1–4). A surgical procedure was subsequently performed.

For diagnosis and discussion, see the following page.

DIAGNOSIS: Small-bowel lymphoma related to acquired immunodeficiency syndrome (AIDS).

DISCUSSION

Primary malignant small-bowel neoplasms are rare, constituting only 2% of primary gastrointestinal malignancies (1). Their diagnosis is often complicated by vague or nonspecific symptoms, and they are usually diagnosed at an advanced stage. At the time of diagnosis, <50% of these tumors are resectable for cure (1).

Malignant small-intestine lymphoma has an estimated annual incidence of 0.12 per 100,000 persons, and it represents approximately 20% of primary malignancies of the small intestine (1). Small-bowel lymphoma is considered to be primary if the predominant lesion is in the intestine and the initial presenting symptoms are related to intestinal involvement. The ileum is the most frequent location for primary intestinal lymphoma because of the increased amount of lymphoid tissue in this site (1). Disorders that predispose patients to small-bowel lymphoma include previous extraintestinal lymphoma, chronic lymphocytic leukemia, celiac disease, and immunologic dysfunction, including AIDS.

Recently, the incidence of small-bowel lymphoma related to B-cell dysfunction and proliferation in human immunodeficiency virus (HIV)–positive patients has increased. Two theories are proposed to explain the pathogenesis of lymphoma in AIDS patients. The first states that ongoing B-cell proliferation induced by HIV in the immunocompromised patient leads to mutations in oncogenes or tumor suppressor genes and therefore the development of lymphoma. The second theory links B-cell dysfunction to increased risk of malignancy. Within the gastrointestinal tract, the ileum contains Peyer's patches, which are lymphoid aggregates that contain B lymphocytes and produce secretory IgA. With HIV infection, helper T-cell depletion leads to reduced IgA production, and, as a result, the gastrointestinal tract and abdominal viscera are potentially at increased risk for neoplasm (2).

Lymphoma is the second most common malignant neoplasm in AIDS patients, after Kaposi's sarcoma. Non-Hodgkin's lymphoma is more common than Hodgkin's or Burkitt's lymphoma. Clinical presentation includes abdominal pain, diarrhea, weight loss, intestinal bleeding, and a palpable mass. Major complications include hemorrhage, perforation complicated by peritonitis, and fistula formation (1).

AIDS patients who have small-bowel B-cell lymphoma tend to present with unusually aggressive, highly advanced disease at the time of diagnosis. For this reason, AIDS-related small-bowel lymphoma carries a poor prognosis and an overall 5-year survival rate of approximately 36% (2).

Barium-contrast radiographic studies have long been the primary diagnostic imaging tool in small-bowel lymphoma (1). A dedicated small-bowel series will reveal multiple features, including luminal narrowing with mucosal destruction, aneurysmal dilatation, thickening of the valvulae conniventes, and multiple intraluminal filling defects (Figure 2). Aneurysmal dilatation is pathognomonic of small-bowel lymphoma and refers to a segmentally dilated intestinal lumen with associated wall thickening and without proximal bowel dilation (Figure 2). Computed tomography (CT) is most commonly used for evaluation, diagnosis, and staging of small-bowel lymphoma. CT findings include mural infiltration of the small-bowel wall with associated homogenous, asymmetric wall thickening (>2 cm) and a nodular appearance of the mass (Figure 3). On CT, lymphoma is softer and longer than adenocarcinoma (with which it is often confused), and it has ill-defined, thickened walls with irregular or complete loss of the normal mucosal folds (3). In addition, CT often reveals mesenteric or retroperitoneal lymphadenopathy (Figure 4), a hallmark of this disease.

Staging in small-bowel lymphoma is based on contiguous, regional, and distal lymphomatous involvement, as well as cell pathology. Therapy consists of surgical removal of tumor with adjuvant chemotherapy.