Tumors of the Intestines Quiz

Tumors of the Intestines

• Topics discussed include tumors of the small intestine, large intestine, gastrointestinal lymphoma, and tumors of the appendix.

Tumors of the Small Intestine

• Rare, comprising 3-6% of gastrointestinal tumors.
• Benign tumors include leiomyoma, adenomatous polyps, and lipoma.
• Malignant tumors include carcinoid tumors and adenocarcinoma.

Carcinoid Tumor

• Originates from neuroendocrine cells (argentaffin cells) distributed throughout various organs.
• Common sites include the appendix (most common), ileum, rectum, stomach, and lungs.
• Gross appearance: small, firm, yellow-brown, intramural or submucosal, solitary in the appendix and rectum, multiple in other areas.
• Microscopic features: islands or sheets of small uniform cohesive cells with scant granular cytoplasm and stippled nuclei. The cells are separated by dense fibrous stroma and stain positive for neuroendocrine markers (e.g., chromogranin).
• Clinical findings: typically asymptomatic; potential for secretory products leading to Zollinger-Ellison syndrome (gastrin), Cushing syndrome (corticotropin), or carcinoid syndrome (serotonin). Laboratory findings may include increased 5-hydroxyindoleacetic acid (5-HIAA) in the urine.
• Carcinoid syndrome features: cutaneous flushing, diarrhea, abdominal cramps, bronchoconstriction, hepatomegaly (due to metastases), and tricuspid and pulmonary valve fibrosis.

Adenocarcinoma of the Small Intestine

• Rare.
• Commonly encircles the bowel.
• Arises in the duodenum.
• Risk factors include celiac disease, Crohn's disease, and diverticulosis.

Tumors of the Large Intestine: Benign Tumors - Neoplastic Polyps (Adenomas)

• Can be sessile or pedunculated.
• Predominantly located in the rectum and sigmoid colon.
• Types include tubular, villous, and tubulo-villous.

Familial Polyposis (Adenomatous Polyposis Coli, APC)

• Hereditary autosomal dominant disease.
• Characterized by hundreds of polyps in the colon (and possibly other sites in the gastrointestinal tract).
• Mutations in the APC gene (chromosome 5) or the MUTYH gene (chromosome 1).
• Virtually 100% will develop invasive adenocarcinoma by age 40.
• Polyp formation is a precancerous condition.

Large Intestine: Non-Neoplastic Polyps

• Hyperplastic polyps.
• Hamartomatous polyps (juvenile or retention polyps).
• Inflammatory polyps (pseudopolyps).
• Lymphoid polyps (hyperplasia of submucosal lymphoid tissue).

Large Intestine: Malignant Tumors

• Carcinoma.
• Malignant lymphoma.
• Leiomyosarcoma.

Colonic Carcinoma

• Worldwide high incidence in industrial areas.
• Higher frequency in males (2:1).
• Age incidence: 50-70 years.
• Risk factors: low fiber diet, high carbohydrate diet, high red meat and animal fat consumption, adenomatous polyps, hereditary polyposis, and ulcerative colitis.
• Common sites and incidence:
  • Rectosigmoid colon: 55%
  • Cecum and ascending colon: 25%
  • Transverse colon: 12%
  • Descending colon: 8%
• Gross appearance:
  • Polypoid type: ascending colon
  • Ulcerative type: any site
  • Infiltrative type: descending colon and rectum; complicated by stenosis and obstruction
• Microscopic features: commonly adenocarcinoma (which may be well-differentiated, undifferentiated, mucoid, or signet ring cells); squamous cell carcinoma; or carcinoid tumor.
• Clinical manifestations: initially asymptomatic; fatigue, weakness, iron deficiency anemia, abdominal discomfort, and progressive bowel obstruction.
• Spread: direct spread to the wall; lymphatic spread to mesenteric and periaortic nodes; blood spread to liver, lung, brain, and bone; and transcelomic spread to the ovary (Krukenberg tumor).
• Prognosis: 100% 5-year survival in lesions limited to the mucosa. 25% 5-year survival in invasive tumors.

Intestinal Lymphoma

• Gastrointestinal lymphoma is a B-cell type lymphoma arising from mucosa-associated lymphoid tissue (MALT).
• Stomach: 55%
• Small intestine: 25%
• Colon: 20%
• Gross appearance: early lesions are plaque-like; advanced lesions are full mural thickness or polypoid protruding into the lumen.
• Microscopic: neoplastic lymphocytes infiltrate and replace normal structures.

Appendicular Tumors

• Carcinoid tumor (common).
• Mucinous cystadenoma (rare): secretes mucus; may rupture; forms mucocele.
• Mucinous cystadenocarcinoma (rare): peritoneal implants; neoplastic mucin-producing cells; pseudomyxoma peritonei (fatal).