Pathology colorectal carcinoma

Question 1

What is a polyp?

Answer 1

A protrusion above an epithilial surface.
It is a tumour (swelling)
Can be benign or malignant

Question 2

How can you tell if a polyp is benign or malignant?

Answer 2

Histopathology

Question 3

What are the types of malignant epithilial polyps?

Answer 3

Polypoid adinocarcinomas (more common)
Carcinoid polyps

Question 4

What are the types of Benign epithilial polyps?

Answer 4

Neoplastic- adenoma (Majority)
Inflamatory- IBD
Hamartomaous-Juvenile or Peutz-Jeghers syndrome
Metaplastic

Question 5

What other polyps can be found in the colon, except epithilial?

Answer 5

Mesenchymal- these are rare compared to epithilial though

Question 6

What is the differential diagnosis in order of likelihood of a colonic polyp?

Answer 6

1) Adenoma
2) Serrated polyp
3) Polypoid adenocarcinoma
4) Other rare thing

Question 7

What are the macroscopic appearances of polyps?

Answer 7

Pedunculated
Sessile
Flat
NB: Sessile and flat are much harder to excise than pedeunculated polyps

Question 8

What are macroscopic features of pedunculated and sessile polyps?

Answer 8

Pedunculated: Irregular surface
Long stalks
Sessile: Look like seaweed and slightly raised

Question 9

Are adenomas dysplastic?

Answer 9

Yes- mostly clonal epithilium without goblet cells

Question 10

Adenomas are benign, non invasive and do not metastatise. Can they transform into malignant tumours?

Answer 10

Yes. They are the precursors to polypoid adenocarcinomas and are premalignant

Question 11

The microscopic architecture of adenomatous polyps is variable. Give 3 examples?

Answer 11

Tubbullovillous, Villous, Tubular.

All dysplastic to a greater or lesser degree and this can be graded.

Question 12

How do adenocarcinomas come about?

Answer 12

Normal mucosa -> Adenoma (dysplastic) -> Adenocarcinoma (invasive)

Question 13

The development of an adenocarcinoma is due to step wise accumulation of genetic injury. What are some of the common genetic mutations at each stage?

Answer 13

Normal epithilium: APC mutation, MCC mutation, 5c deletion
Small adenoma: K RAS mutation
Large adenoma: Chromosome 17p,18q deletions, p53 mutations
Adenocarcinoma

Question 14

All adenomas must be removed?

Answer 14

Yes because they are premalignant- within reason (patient age, fitness etc.)

Question 15

How are adenomas removed?

Answer 15

Endoscopy or surgery

Question 16

Do all colorectal adenomas have the same molecular genetic origins?

Answer 16

No- separate pathways for inherited tumours and serrated adenomas

Question 17

What is the primary treatment for adenocarcinoma?

Answer 17

Surgical resection. Following a biopsy and CT scan to stage the disease.
The resected specimin is removed and sent to pathology for staging

Question 18

Histopathology:

Red is dead, blue is bad?

Answer 18

Red/pink is necrosis

Blue is lots of DNA

Question 19

What is dukes stage A, B and C for colorectal cancer?

Answer 19

A = Confined by the muscularis propria (Good prognosis)
B = Through muscularis propria
C = Metastatic to lymph nodes (poor prognosis)

Question 20

Will Dukes stage A, B or C need further treatment following surgical resection?

Answer 20

A probably not
B dependent on patient and features of tumour
C Yes will need further chemo therapy

Question 21

What are the symptoms of left sided (Rectum, sigmoid and descending colon) colorectal carcinoma?

Answer 21

Blood PR, Altered bowel habit (alternating diarrhoea and constipation), Obstruction

Question 22

What are the symptoms of right sided (Caecum and ascending colon) colorectal carcinoma

Answer 22

Anaemia and weight loss. No blood PR because even if bleeding the blood will be absorbed back in the colon.
No obstruction because the tumour can grow nearly across the whole lumen and the liquid from the ileum will still get through.
Tumours in the caecum can grow very large and be assymptomatic

Question 23

What is the gross and histopathological appearance of colorectal carcinoma?

Answer 23

Gross appearance is variable: polypoid, stricturing, ulcerating.
Typical histological appearance of adenocarcinoma as they have common genetic abnormalities

Question 24

How does colorectal cancer sprea?

Answer 24

Local invasion: Mesorectum, peritoneum, liver, other abdominal organs
Lymphatic spread: Mesenteric nodes
Haematogenous: Liver (All but the final 1/3 or the recum drains in to the hepatic portal vein, distant sites.

Question 25

What are the 2 types of inherited colorectal cancer syndrome?

Answer 25

Lynch syndrome

Familial Adenomatous Polyposis (FAP)

Question 26

What are the characteristics of Lynch syndrome?

Answer 26

<100 polyps
Cancer in 50s and 60s (later onset)
Rght sided tumours
Mucinous tumours with a crohn’s like inflammatory response

Question 27

What is the management of lynch syndrome?

Answer 27

Colonoscopy for life and females will have a prophylactic hysterectomy after completing their family as its associated with gastric and endometrial carcinomas

Question 28

What are the genetic abnormalities in lynch syndrome?

Answer 28

Autosomal dominant (Every cell already has 1 allele and only needs one more)
Defect in mismatch repair.
Inherited mutation in MLH 1, MSH 2, PMS 1 or MSH 6

Question 29

What are the characteristics of Familial Adenomatous polyposis?

Answer 29

Early onset in 20s
>100 polyps
Adenocarcinomas 
No specific inflammatory response
Associated with desmoid tumours and thyroid carcinoma

Question 30

What are the genetic abnormalities in Familial Adenomatous Polyposis?

Answer 30

Autosomal dominant
Defects in tumour suppression
Inherited mutation in the FAP gene.

Question 31

How is FAP managed?

Answer 31

Colonectomy before aged 21 and unlikely to maintain continence. Alternative = they WILL get cancer. Counselling and screening