Pathology
Lecture 46 Intestinal Neoplasms
1)To be familiar with neoplasms of esophagus, specifically squamous cell carcinoma and adenocarcinoma, including predisposing factors, clinical features, and pathologic findings.See table from Lecture 41 question 5.
2)To know the types of neoplasms affecting the small intestine.
Benign: adenomas, mesenchymal tumors, lipomas, angiomas, and hemartomatous mucosal lesions.
Malignant: adenocarcinomas, carcinoids, lymphomas and sarcomas.
3)To know the types of adenomas affecting the small bowel.
Most adenomas occur in the region of the ampulla of Vater. They account for 25% of benign small intestinal tumors, present in 30-60 year old patient with a call to blood loss, rarely with obstruction.
4)To be familiar with the nature of carcinoid tumors, their distribution, biologic behavior, and clinical course, and pathologic findings of carcinoid.
Carcinoid tumors are carcinoma like the with a much more indolent clinical course. They are derived from resident endocrine cells, with the GI tract and the lung as the predominant sites of occurrence. Mucosal endocrine cells generate bioactive compounds, particularly peptide and nonpeptide hormones, and play a major role and coordinated gut function. Five-year survival is 90%.
Distribution: primarily in the GI tract with <2% of colorectal but almost 50% of small intestine malignant tumors. A few arise in the pancreas or parapancreatic tissue, lungs, biliary tree, and even liver.
Biologic behavior: carcinoid tumors may be confined to the mucosa and submucosa or may be malignant in behavior with the invasion and metastatic spread to regional lymph nodes and the liver. Benign and malignant tumors cannot be differentiated histologically, but rather by site of origin, with appendix and rectum rarely metastasizing while 90% of ileal, gastric, and colonic will metastasize.
Clinical course: many are asymptomatic, however the secretory products may produce a variety of syndromes, like Zollinger-Ellison syndrome (excess gastrin), Cushing's syndrome (corticotropin), and hyperinsulinism.
Pathologic findings: intramural or submucosal masses that create small, polyploid or plateau-like elevations rarely more than 3 cm in diameter. Mucosa may be intact or ulcerated, and the tumors may permeate the bowel wall. They may cause angulation or kinking sufficient to cause obstruction. Histologically, sales form discrete islands, tribute to a, stands, and glands, or undifferentiated sheets. Cells have scant, pink granular cytoplasm and a round to oval stippled nucleus (mitosis infrequent).
5)To know the features and proposed mechanisms of carcinoid syndrome.Carcinoid syndrome (1% of all, 20% of metastatic) is thought to arise from excess serotonin, 5-HT, as well as other factors (histamine, bradykinin, kallikrein, and prostaglandins). GI carcinoids require hepatic metastases for progression of carcinoid syndrome due to extensive metabolism of 5-HT to its metabolite 5-HIAA. Extraintestinal carcinoids do not require hepatic metastasis.
6)To know the general types of lymphoma that are primary in the gastrointestinal tract.B cell lymphomas arising from the mucosa-associated lymphoid tissue (MALT), Mediterranean lymphoma, and intestinal T cell lymphoma (associated with malabsorption syndromes).
7)To be aware of the symptoms, gross and microscopic findings in adenocarcinoma of the small intestine.
Symptoms: obstructive jaundice (associated with the ampulla of Vater), intestinal of structured, cramping pain, nausea, vomiting, and weight loss. A cold blood loss may be the only sign.
Gross: tumor penetrating the bowel wall and invading the mesentery or other segments of the gut, spread to regional lymph nodes, and sometimes metastasized to the liver.
Micro: composed of high-grade dysplastic or neoplastic epithelium, which lines glands as tall, hyperchromatic, somewhat disordered epithelium that may or may not show mucin vacuoles.
8)To be familiar with the general types of neoplasms affecting the colon.
Benign: adenomas (polyps), leiomyomas, lipomas
Benign or malignant: carcinoids
Malignant: adenocarcinoma
9)To understand the various types of colonic adenomas, their pathologic findings, and their respective risk for development of adenocarcinoma.
Tubular adenoma (most common 75%) are usually small and pedunculated, usually arising in men>60 years, and the rectosigmoid region. Micro: closely spaced glands with crowded cells, decreased mucin production and "migration" of nuclei. Very low risk of carcinoma development (~1% is lesion is <1 cm).
Villus adenoma contains >50% villous, usually rectosigmoid. Patient is usually 60-65. Usually sessile (broad-based); frond-like profile. Micro: "fronds" composed of connective tissue core covered by colonic epithelium; varying degrees of nuclear atypicality. Risk of carcinoma is ~10% when <1 cm and >50% for >2 cm (invasive).
Tubulovillus adenoma has hybrid features of tubular villus adenomas. Risk of developing carcinoma is proportionate to villus element.
10)To be familiar with the factors affecting the risk of carcinoma arising in an adenoma.Factors affecting the risk include: size, proportion of villus component, and degree of cytologic atypia.
11)To understand the epidemiology of adenocarcinoma of the colon.
Second-most common carcinoma in US males (lung is first). Industrialized >developing countries, immigrants adopt higher incidence. Dietary factors: low-fiber, high-refined carbohydrate, high-fat. Urban >rural. Peak age 60s.
12)To know the distribution, growth features, and presenting symptoms of adenocarcinomas of the colon in the context of left-sided vs. right-sided primary sites.
Distribution: majority a rise in rectosigmoid colon.
Left-sided carcinomas generally annular, constrictive, and often present with obstruction.
Right-sided carcinomas generally polyploid, are more likely to present with bleeding.
13)To know the risk factors associated with adenocarcinomas of the colon. To know the pathologic findings of adenocarcinoma of the colon, including colloid carcinoma.
Risk factors: prior colorectal carcinoma, adenomas (particularly villus), and ulcerative colitis.
Pathologic findings: gross - right and left sided appearance (above). Micro - moderately too well differentiated with recognizable gland formation and mucin production; bowel invasion, desmoplastic fibrotic reaction.
Colloid carcinoma: abundant mucus production with floating malignant cells, poorer prognosis.
14)To understand the general features of adenocarcinoma of the colon with respect to prognosis, including the Dukes’ staging classification.
Prognosis: correlated with extent of invasion through bowel wall, lymph node in distant metastases.
Astler-Coller (modification of Dukes-Kirklin):
- Confined to mucosa
- Invasion of muscularis proper (B1 superficial; B2 through entire wall)
- Local lymph node metastasis (C1 with extension into muscularis, C2 through wall)
- Distant metastasis
Five-year survival rate ~40% (60% for Dukes’ B, 35% for Dukes’ C)
15)To be generally familiar with the kinds of carcinoma affecting the anal canal.
Carcinomas of the anal canal are frequently squamous cell carcinomas; some are cloacogenic or transitional cell carcinomas.
16)To know the general types of neoplasms affecting the appendix.
Neoplasms of the appendix are usually carcinoids (often arising at the tip), cystadenomas and cystadenocarcinomas (rarer producing mucus dilation of the appendix spillage into the peritoneum).
17)To be familiar with all information contained in handout on Gastrointestinal Neoplasms (excluding stomach). Review handout.