Sigmoid polyp specimen

Question 1

Describe the case for your specimen?

Answer 1

Case: 65-year-old woman presents with small amount of frank blood on stools and change in bowel habit.

Question 2

Describe the process of specimen preparation and examination?

Answer 2

• Single polyp from sigmoid mucosa identified
• Submucosal injection of adrenaline and methylene blue
-> induced local vasospasm -> reducing bleeding and retaining polyp stalk
• Polyp removed by electrocautery and fixed in formalin
• Area checked for bleeding and perforation
• Lab sectioning
- Base of stalk stained with black dye
- Polyp sectioned into 3 longitudinal segments by dissecting either side of stalk

Question 3

Describe the macroscopic appearance of the sigmoid polyp?

Answer 3

Macroscopic appearance:
• Brown polyp measuring 30x25x25 mm
• Stalk 12x6mm
• Possible malignant features; pale appearance, large size (increased proliferation -> solid tumour with poor perfusion)
• Pedunculated (lobular head, slender stalk)
• Pale with limited perfusion
• Smooth mucosal surface with signs of ulceration and haemorrhage

Question 4

Describe the microscopic appearance of the sigmoid polyp?

Answer 4

Microscopic appearance:
• Architecture
- Tubular gland forming cells w moderate differentiation and fibrous desmoplastic response
- Ulceration and haemorrhage of epithelium
- Abnormal cells extend beyond muscularis mucosa and lamina propria -> suggest intramucosal carcinoma

• Cellular

• Severely dysplastic tall columnar cells of colonic mucosa
• Neoplastic features: hyperchromatic nuclei, multiple mitotic figures, increased N:C ratio, pleomorphism

Question 5

Describe the pathogenesis of sigmoid polyp formation?

Answer 5

1) Trigger (normally sporadic): inactivation of tumour suppressor genes (APC and p53) an activation of proto-oncogene (KRAS)
- other causes (genetic/non-sporadic): familial colonic adenocarcinoma, hereditary non-polyposis CRC or familial adenomatous polyposis
2) Increased mitotic cell division
3) Uncontrolled cell growth