MRCS Part B Revision · Surgical pathology
Colonic Carcinoma — MRCS Part B Surgical pathology
By Dr Richard Miller, MBChB FRCS · Reviewed
Colonic Carcinoma is a surgical pathology station. Two of the seventeen examined stations in the MRCS Part B OSCE are surgical pathology. The surgical pathology stations ask you to reason from a specimen, a slide, a report or a vignette to a diagnosis, and then to say what it means for the patient in front of you.
What you need to know for the Colonic Carcinoma station
A man with a change in bowel habit and a family history of colitis, whose barium enema shows a lesion. Colorectal cancer from polyp to Dukes stage.
Investigation
Colonoscopy and biopsy is the investigation of choice, seeing the whole colon for synchronous lesions (about 3–5%). CT colonography if the colonoscopy is incomplete or the patient frail. Staging: CT of chest, abdomen and pelvis; MRI of the pelvis for rectal cancer to assess the mesorectal margin; CEA as a baseline for follow-up.
Risk factors
Age, adenomatous polyps, a family history, the inherited syndromes (familial adenomatous polyposis from APC mutation; Lynch syndrome from mismatch repair genes, with right-sided tumours), long-standing ulcerative colitis or Crohn's colitis, a previous colorectal cancer, obesity, a diet high in red and processed meat and low in fibre, smoking, alcohol and acromegaly.
Distribution and symptoms
About two-thirds are in the rectum and sigmoid, a fifth in the caecum and ascending colon, the rest in between; right-sided tumours are becoming relatively commoner. Right-sided tumours grow in a wide, liquid-filled lumen and present with iron-deficiency anaemia, a mass and weight loss. Left-sided tumours present with a change in bowel habit, rectal bleeding, mucus, tenesmus, and obstruction. Any of them can present as an emergency with obstruction or perforation.
Polyps and the adenoma-carcinoma sequence
Most cancers arise in an adenoma over five to ten years, through a sequence of mutations: APC (loss of the “gatekeeper”, the first step), KRAS activation, loss of SMAD4 and then TP53. Polyps are adenomatous (tubular, tubulovillous or villous), serrated (hyperplastic, which are innocent, and sessile serrated lesions, which are not), hamartomatous (juvenile, Peutz-Jeghers) and inflammatory. Malignant potential rises with size (over 2 cm, about 40% contain cancer), with villous architecture, with high-grade dysplasia, and with a sessile rather than pedunculated shape.
Pathology and screening
Adenocarcinoma in nearly all; a biopsy at sigmoidoscopy will show it, graded by differentiation. The English screening programme offers a faecal immunochemical test every two years from 50 (extending down from 60), with colonoscopy for a positive result; flexible sigmoidoscopy at 55 was the earlier programme. Colonoscopic surveillance is offered to those with polyps, colitis or a family history.
Staging and treatment
Dukes A is confined to the bowel wall, B through the wall with no nodes, C with nodes (C1 apical node clear, C2 involved), D distant spread; five-year survival is roughly 90, 70, 40 and under 10%. In TNM, a tumour through the wall without nodes is T3 or T4 N0, stage II. Treatment is resection with the lymphovascular pedicle (right hemicolectomy, left hemicolectomy, sigmoid colectomy, anterior resection or abdominoperineal excision for the rectum, and total mesorectal excision for rectal tumours), with adjuvant chemotherapy for node-positive disease and for high-risk stage II, and neoadjuvant chemoradiotherapy for rectal tumours threatening the margin. Liver metastases can be resected. Obstruction is treated by resection, defunctioning stoma or a stent as a bridge.
Images from this station
What are you asked at the Colonic Carcinoma station?
The station runs to 18 questions over nine minutes. These are the questions as they are put to you; the model answers are in the question bank.
- In this scenario you will be asked a series of questions relating to this case. Pathology: Colonic Ca
- What does the study demonstrate?
- How would you further investigate this gentleman?
- What are the risk factors for colonic malignancy?
- What is the distribution of colon tumours around the bowel?
- What symptoms might a patient with colorectal cancer present with?
- The patient undergoes biopsy at sigmoidoscopy. What type of tumour is this likely to be?
- What is the relationship between polyps and colon cancer?
- What types of polyps can be found in the bowel?
- How does the size and shape of an adenomatous polyp relate to its malignant potential?
- What screening methods exist for detecting bowel cancer?
- Following a CT scan and sigmoidoscopy the patient is found to have a colorectal carcinoma that has spread through the bowel wall but is yet to reach lymph nodes. How can colorectal cancer be staged using this information and what is the prognosis of this patient?
And 6 more at this station.
How is the surgical pathology station marked in MRCS Part B?
Like the anatomy stations, a surgical pathology station is marked out of 20 with all 20 marks going to clinical knowledge and its application. The second of the two may be a microbiology station.
FAQ
What does the Colonic Carcinoma station ask?
It opens with "In this scenario you will be asked a series of questions relating to this case. Pathology: Colonic Ca" and runs to 18 questions over nine minutes. Like the anatomy stations, a surgical pathology station is marked out of 20 with all 20 marks going to clinical knowledge and its application. The second of the two may be a microbiology station.
How many pathology stations are in MRCS Part B?
Two of the seventeen examined stations. The intercollegiate blueprint titles the second one surgical pathology and/or microbiology, so infection and antimicrobial topics appear here rather than in a station of their own.
How is the pathology station marked?
Out of 20, with every mark awarded for clinical knowledge and its application. There are no communication or professionalism marks available in it.
What should I revise for surgical pathology?
The general processes the syllabus names, inflammation, healing, neoplasia and infection, applied to the specimens and reports a surgical trainee meets. Candidates most often report malignancies and their mutations, inherited cancer syndromes, and obstructive jaundice.
How many stations are in the MRCS Part B OSCE?
Seventeen examined stations of nine minutes each, with a minute to read the task before each one. Two preparation stations and at least one rest station bring the circuit to about twenty, and the exam takes about three and a half hours.
What is the pass mark for MRCS Part B?
There is no published pass mark. The cut score is set separately for Applied Knowledge and Applied Skills, for each circuit, by borderline regression. Published pass rates across the 2024/25 diets ranged from 51% to 66%.
Can I fail a station and still pass?
Yes. There is no rule about how many stations you may fail: the cut score applies to your total mark in each component, so a weak station costs the marks you lost on it and strong stations elsewhere can make them back. Applied Knowledge and Applied Skills are passed separately and must both be passed at the same sitting, so a strong anatomy performance cannot rescue a weak communication one.
Dr Richard Miller, MBChB FRCS
Station summaries are reviewed against the current intercollegiate MRCS syllabus and the published marking blueprint. Guidance changes between diets: check the royal colleges' own pages before relying on a date, a fee or a threshold.
Practise this station
The question bank carries the model answer to every question above, with the rest of the surgical pathology stations.
More surgical pathology stations