Tumours of the Lower GI Flashcards
What are the benign and malignant tumours of the small intestines
Benign - Adenoma (25%) and mesenchymal tumours (leiomyoma, lipoma and angioma)
Malignant - Angiocarcinoma and carcinoid. Lymphoma and sarcomas
What are the benign and malignant tumours of the colon and rectum
Benign - Non neoplastic polyps and neoplastic polyps (adenoma)
Malignant - Adenocarcinoma, carcinoid, anal zone carcinoma, lymphoma and leiomyosarcomas.
Describe features of an adenoma of the small intestine
- Benign tumour of glandular cells. It usually effects the ampulla of Vater in the duodenum and has malignant potential to become an adenocarcinoma.
Describe features of adenocarcinomas of the small intestines
- Malignant tumours of glandular tissue.
- Polypoid exophytic masses which can cause intestinal obstruction.
- Symptoms include cramping pain, nauseas, vomiting, weight loss and may have obstructive jaundice.
Define;
- hyperchromasia,
- Pleomorphism,
- Dysplasia,
- Mitotic figures
- Hyperplasia
Hyperchromasia - Nucleus that looks darker,
Pleomorphism - Variability in shape and size,
Dysplasia - Abnormal development of cells,
Mitotic figures - lack of a nuclear membrane.
Hyperplasia - Increase in the number of cells
Describe features of the benign tumours of the colon and rectum?
Non-neoplastic polyps - Hyperplastic and hamartomatous.
Neoplastic (adenoma) - Tubular, villous or tubulovillous
In further detail explain the histology and other clinical features of hyperplastic (non-neoplastic) polyps
- Well formed glands and cryps which are lined by non-neoplastic epithelial cells. Most show differentiation into goblet or absorptive cells. No malignant potential
In further detail explain the histology and other clinical features of Juvenile hamartomatous polyps
- Malformations of the mucosal epithelium and lamina propria. Occurs in children under age 5.
- Histologically; Crystically dilated glands, inflammation and surface can be ulcerative.
In further detail explain the histology and other clinical features of Peutz-jeghers hamartomatous polyps
Autosomal dominant syndrome which involves mucosal epithelium, lamina propria and muscularis mucosa. Tend to be large and pedunculated. No malignant potential but does increase risk of pancreas, breast, lung, ovary and uterus carcinoma
Describe what the risk of an adenoma turning into an adenocarcinoma is correlated with?
- Polyp size (greater size = greater risk)
- Histological architecture,
- Severity of dysplasia
Describe the morphology of tubular adenomas
Small - Smooth contoured and sessile where as large ones tend to be lobular and have stalks.
Histologically - the stalk is comprised of fibromuscular tissue and BVs. Dysplastic epithelium which lines glands.
Describe the morphology of villous adenomas
They have a velvety or caultiflower-like projection and commonly effects the rectum and rectosigmoid colon.
Histologically - Villiform extensions of mucosa, covered by dysplastic columnar epithelium. When invasive carcinoma occurs there is no stalk to act as a buffer zone to invasion is directly onto wall of colon.
Describe clinical features of neoplastic polyps (adenomas)
Tubular and tubulovillous adenomas may be asymptomatic and are commonly discovered in evaluation of anaemia or bleeding. Villous adenomas are more symptomatic and is often discovered due to rectal bleeding.
Endoscopic removal of a pedunculated adenoma is regarded as adequate if;
1) The adenoma is superficial and does not approach the margin of excision across the base of the stalk,
2) There is no vascular or lymphatic invasion,
3) The carcinoma is not poorly differentiated
What is the significance of familial adenomatous polyposis syndrome?
Genetic mutation which causes of a high number of polyps which tend to be tubular adenomas. There is a 100% risk of developing adenocarcinoma before age 30 = total colectomy indicated.
What are the dietary factors for development of a carcinoma
1) Excess dietary caloric intake,
2) Low content of vegetable fibre,
3) High content of refined carbohydrates,
4) Intake of red meat,
5) Decreased intake of protective micronutrients
Where are the most common sites of colorectal carcinoma
1) Rectosigmoidal colon,
2) Caecum/ascending colon,
3) Transverse colon,
4) Descending colon
Describe the morphology of tumours in the proximal colon
Polypoid, exophytic masses. Obstruction is uncommon but it can penetrate bowel wall.
Describe the morphology of tumours in the distal colon
Annular, encircling lesions. Lumen is markedly narrowed and proximal bowel may be distended. Can penetrate bowel wall as subserosal and serosal white firm masses
Describe the histology of colorectal carcinomas
Can range from tall columnar cells to undifferentiated anaplastic masses.
What are some of the clinical features (symptoms) of colorectal carcinomas
- Can be asymptmatic for years.
- Right colonic - Fatigue, weakness and iron-deficiency anaemia.
- Left sided lesions - bleeding, changes in bowel habits or crampy left lower quadrant discomfort
Explain Dukes staging
A) Confined to submucosa or muscle layer,
B) spread through muscle layer but does not yet involve lymph nodes,
C) Involving lymph nodes
What are carcinoid tumours and what does their aggressive behaviour correlate with?
Derived from endocrine cells. Aggressive behaviour correlates with;
- Site of origin,
- Depth of local penetration,
- Size of tumour,
- Histological features of necrosis and mitosis
Describe the morphology and histology of carcinoid tumours
- Usually a solitary lesion which has a yellow/tan appearance. Most commonly found in the appendix
Histology - Neoplastic cells may form discrete islands which have a pink granular cytoplasm and round oval nucleus
What are the clinical features of carcinoid tumours?
Rarely produce local symptoms but can cause carcinoid syndrome which is due to excessive serotonin. It causes flushes and cyanosis, diarrhoea, cramps, N/V and resp symptoms. Appendiceal and rectal carcinoids do NOT metastasize
What is the definition of gastrointestinal lymphoma?
Primary GI lymphomas exhibit no evidence of liver, spleen, mediastinal LN or bone marrow involvement at time of diagnosis.
Explain what B cell and T cell lymphomas are associated with?
B-cell - MALT, Immunoproliferative small intestineal disease and burkitt lymphoma.
T-cell - long standing malabsorption syndrome.
Name and describe some mesenchymal tumours
Lipomas - Arise in submucosa or muscularis propria.
Leiomyomas,
- Leiomyosarcomas - Large, bulky, intramural mases that eventually fungate and ulcerate into the lumen or abdo space
Describe tumours of the anal canal
Benign - Warts
Malignant - Basaloid pattern, squamous cell carcinoma (associated with HPV), adenocarcinoma (extension of rectal adenocarcinoma) and malignant melanoma (very rare)
