Small bowel lymphoma

Small bowel lymphoma is one of the most common small bowel malignancies, accounting for ~25% of all primary small bowel malignancies, and ~40% of all primary gastrointestinal lymphomas.

Epidemiology

Small bowel lymphoma is most commonly secondary extranodal involvement in widespread systemic lymphoma. When primary it is seen predominantly in well-defined patient groups, and the demographics, therefore, match those groups. Predisposing conditions include ¹:

• HIV/AIDS
• celiac disease
• organ transplant (see post-transplant lymphoproliferative disorder (PTLD))
• Helicobacter pylori positive patients

Clinical presentation

The presentation is variable and includes ¹:

• gastrointestinal hemorrhage
• perforation
• small bowel obstruction (uncommon)

Pathology

The type of lymphoma depends on the underlying predisposing condition.

• H. pylori:  mucosa-associated lymphoid tissue lymphoma (MALToma)
• PTLD: polyclonal B-cell non-Hodgkin lymphoma (EBV-associated)
• HIV: B-cell non-Hodgkin lymphoma ³, overall most common type
• T-cell lymphomas are seen but are uncommon ⁵; they have a greater tendency to perforate

Location

The most common sites are the ileum (60-65%) and jejunum (20-25%) ⁷.

Radiographic features

Typically, small-bowel lymphoma involves a single loop of bowel, with 5-20 cm of its length demonstrating ³:

• bowel wall thickening: 1-7 cm
• aneurysmal (or pseudoaneurysmal) dilatation (30%): occurs due to the replacement of muscularis by tumor or infiltration of myenteric nerve plexus ⁶

Despite the extensive involvement, small bowel obstruction is uncommon because of lack of desmoplastic reaction, and perforation is rare.

Regional lymph node enlargement in approximately 50% of cases.

Less frequently, the disease may manifest as a solid mass lesion (polypoidal/excentric). Differentiation from adenocarcinoma may be difficult. However, the presence of extensive retroperitoneal lymphadenopathy and splenomegaly favors lymphoma, whereas adjacent fat infiltration supports adenocarcinoma.

Treatment and prognosis

Most frequently, the involved segment is resected, with subsequent chemoradiotherapy ².

Differential diagnosis

• inflammatory bowel disease, especially Crohn disease
• adenocarcinoma of the small bowel
• metastases
  • melanoma
  • renal cell carcinoma ³
  • breast cancer
  • lung cancer
• infection/enteritis
• leiomyoma/leiomyosarcoma/GIST