Question 1
Most likely diagnosis is adenocarcinoma of the right sided colon.
The palpable mass in the RLQ, anaemia(which is classic of right sided CRC and due to blood loss) and blood in the stool all lead to this diagnosis. It could also explain why the scope couldn’t pass the whole way through the colon. Elevated ESR also suggests malignancy. The patient himself, his age and gender, also are fitting with a diagnosis of CRC.
A change in bowel habits, mucous production and frank bleeding in the stool, as well as nausea and vomiting and constipation or diarrhoea are common symptoms of CRC that weren’t present in this patient.[1]
Between the primary CRC and the secondary microcytic anaemia, which can account for the decreased haemoglobin and exercise tolerance, all the symptoms have been accounted for.
Possible diagnoses
- Crohn’s disease: the patient would experience more severe pain, he would definitely have noticed change in bowel movements and it’s unlikely to be newly diagnosed at his age
- Diverticulosis: generally seen in sigmoid colon, unlikely to be right sided.
Question 2
Predisposing factors are age, where it’s most common in those over 50years, gender and family history of juvenile polyposis syndrome, Peutz-Jeghers syndrome, Lynch syndrome or FAP. Ulcerative colitis, inflammatory bowel disease and Crohn’s disease also increase the risk of developing CRC. [1]
Initiating factors are those of diet and lifestyle. A high intake of refined fats(such as red meat), carbs and alcohol, and a low intake of unabsorbable vegetable fibre, fruit and vegetables are associated with an increase risk of developing CRC[2]. Obesity and smoking have also been linked to CRC[1].
Adenoma-carcinoma sequence: Accounts for 85% of CRC. Both copies of the APC gene which usually degrades β-catenin are knocked out. Without APC, β-catenin builds up and results in a number of mutations, including mutations in KRAS which leads to the development of polyps. The further loss of p53 can result in the adenomous polyps turning carcinogenic.[2][3]
This is usually sporadic but can be genetic. In familial adenomatous polyposis, there is germline knocking out of APC. These patients have hundreds thousands of polyps. If left untreated almost 100% will develop CRC[3][4].
The microsatellite instability pathway: Found in 15% of CRCs. Involves defects of mismatch repair system genes such as MLH1 and MSH2, lead to DNA mismatch repair and an accumulation of mutations. Mutations located in the coding areas for the proteins which are responsible for cell growth, such as TGF-β, which regulates colonic epithelial cell proliferation. Mutated copies of the gene leads to unregulated cell proliferation and subsequent tumour proliferations. Families suffering from Lynch syndrome have germline mutations which will lead to CRC(in 80% of cases) via the microsatellite pathway.[2][3]
Question 3
If left untreated the cancer could progress to form a local obstruction, perforation, peritonitis and ultimately death. It could also travel to the lymphnodes and metastise, most likely to the liver and lungs, again which could lead to the death.
Prognosis depends on the staging. Patients presenting at stage I had a 95% relative survival after 5years, stage II 83%, stage III 64% and stage IV <10%. [5]
[1] Understanding cancer of the colon and rectum. (2001). 6th ed. Dublin: Irish Cancer Society, pp.8-9.
[2] Kumar, V., Abbas, A., Aster, J. and Robbins, S. (2013). Robbins basic pathology. Philadelphia, PA: Elsevier/Saunders, pp.597-598.
[3]Hisamuddin, I. and Yang, V. (2006). Molecular genetics of colorectal cancer: An overview. Current Colorectal Cancer Reports, [online] 2(2). Available at: http://www.medscape.com/viewarticle/482258 [Accessed 25 Oct. 2016].
[4] Cancer.Net. (2016). Familial Adenomatous Polyposis. [online] Available at: http://www.cancer.net/cancer-types/familial-adenomatous-polyposis [Accessed 25 Oct. 2016].
[5]Colorectal cancer incidence, mortality, treatment and survival in Ireland 1994-2010. (2016). [online] NCRI, p.32. Available at: http://www.ncri.ie/sites/ncri/files/pubs/ColorectalCancerIncidenceMortalityTreatmentandSurvivalinIreland1994-2010.pdf [Accessed 25 Oct. 2016].