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Pathology - Colorectal carcinoma
Definition: • A malignant epithelial tumor in the colon or rectum.Tumors that penetrate the muscularis mucosae into the submucosa are considered malignant at this site. In contrast, carcinomas at other sites just require a breach of the basement membrane directly beneath the epithelium to be classified as malignant.
Epidemiology: • Third most frequent cancer in the UK, with a lifetime risk of 1 in 16 males and 1 in 20 women. • Second leading cause of cancer-related deaths. A diet high in animal fat and low in fiber, combined with a sedentary lifestyle, increases risk. Idiopathic inflammatory bowel illness (FAP) and hereditary non-polyposis colorectal cancer (HNPCC) are also linked.
Carcinogenesis: • Most cancers develop through a crypt focus (dysplasia in a single crypt), adenomatous polyp, or invasive carcinoma. • Common genetic aberrations include loss of APC, TP53, and SMAD4. • In some tumors, mismatch repair genes are inactivated, resulting in microsatellite instability. Symptoms include gastrointestinal changes, tenesmus, stomach pain, and iron deficiency anemia. Asymptomatic tumors can be detected by screening or surveillance programs.
Macroscopy reveals that tumors typically develop as polypoid lumps in the gut lumen, with surface ulceration. Some tumors in the distal colon cause circumferential stenosing lesions. • The sliced surface shows a whitish tumor mass with poorly defined edges that penetrates the intestinal wall. • Mucinous carcinomas produce large pools of gelatinous material.
Histopathology • Most cancers are adenocarcinomas, which are malignant epithelial tumors with glandular differentiation. • Well-differentiated tumors exhibit extensive tube formation, while poorly differentiated tumors exhibit little gland formation. • Tumors are typically moderately differentiated and include a high amount of necroinfiltrated detritus within glandular gaps, known as 'dirty' necrosis. Mucinous adenocarcinomas are characterized by significant mucin synthesis in around 10% of colonic and 30% of rectal tumors, resulting in malignant cells floating in huge pools of extracellular mucin.
Prognosis: 5-year survival rate around 50%. • Prognostic markers for tumors include stage, vascular invasion, tumor differentiation, and surgical excision. National Health Service (NHS) bowel cancer screening program. • Provides screening every two years to men and women aged 60-69. • People above the age of 70 are not typically invited, but they can request screening. • Eligible patients receive a faecal occult blood test kit at home, with instructions on how to complete the test and send their sample to the nearest laboratory. • Approximately 2% of individuals have a positive result and are recommended to undergo a colonoscopy. • Of those, 50% have a normal colonoscopy, 40% have a polyp, and 10% have cancer.
TNM 7 Pathological Staging of Colorectal Cancers Primary Tumor (T)
pT1: The tumor invades the submucosa. pT2: The tumor invades the muscularis propria. In pT3, tumors penetrate the subserosa or non-peritonealized pericolic or perirectal tissues via the muscularis propria. pT4a: The tumor perforates the visceral peritoneum. pT4b: The tumour immediately invades another organ or structure.
Regional lymph nodes. (N) pN0 indicates no regional lymph node metastasis. pN1a indicates metastases in one regional lymph node. pN1b refers to metastases in two or three regional lymph nodes. pN2a: metastases in 4-6 regional lymph nodes. pN2b: metastases in seven or more regional lymph nodes.
Definition: • A malignant epithelial tumor in the colon or rectum.Tumors that penetrate the muscularis mucosae into the submucosa are considered malignant at this site. In contrast, carcinomas at other sites just require a breach of the basement membrane directly beneath the epithelium to be classified as malignant.
Epidemiology: • Third most frequent cancer in the UK, with a lifetime risk of 1 in 16 males and 1 in 20 women. • Second leading cause of cancer-related deaths. A diet high in animal fat and low in fiber, combined with a sedentary lifestyle, increases risk. Idiopathic inflammatory bowel illness (FAP) and hereditary non-polyposis colorectal cancer (HNPCC) are also linked.
Carcinogenesis: • Most cancers develop through a crypt focus (dysplasia in a single crypt), adenomatous polyp, or invasive carcinoma. • Common genetic aberrations include loss of APC, TP53, and SMAD4. • In some tumors, mismatch repair genes are inactivated, resulting in microsatellite instability. Symptoms include gastrointestinal changes, tenesmus, stomach pain, and iron deficiency anemia. Asymptomatic tumors can be detected by screening or surveillance programs.
Macroscopy reveals that tumors typically develop as polypoid lumps in the gut lumen, with surface ulceration. Some tumors in the distal colon cause circumferential stenosing lesions. • The sliced surface shows a whitish tumor mass with poorly defined edges that penetrates the intestinal wall. • Mucinous carcinomas produce large pools of gelatinous material.
Histopathology • Most cancers are adenocarcinomas, which are malignant epithelial tumors with glandular differentiation. • Well-differentiated tumors exhibit extensive tube formation, while poorly differentiated tumors exhibit little gland formation. • Tumors are typically moderately differentiated and include a high amount of necroinfiltrated detritus within glandular gaps, known as 'dirty' necrosis. Mucinous adenocarcinomas are characterized by significant mucin synthesis in around 10% of colonic and 30% of rectal tumors, resulting in malignant cells floating in huge pools of extracellular mucin.
Prognosis: 5-year survival rate around 50%. • Prognostic markers for tumors include stage, vascular invasion, tumor differentiation, and surgical excision. National Health Service (NHS) bowel cancer screening program. • Provides screening every two years to men and women aged 60-69. • People above the age of 70 are not typically invited, but they can request screening. • Eligible patients receive a faecal occult blood test kit at home, with instructions on how to complete the test and send their sample to the nearest laboratory. • Approximately 2% of individuals have a positive result and are recommended to undergo a colonoscopy. • Of those, 50% have a normal colonoscopy, 40% have a polyp, and 10% have cancer.
TNM 7 Pathological Staging of Colorectal Cancers Primary Tumor (T)
pT1: The tumor invades the submucosa. pT2: The tumor invades the muscularis propria. In pT3, tumors penetrate the subserosa or non-peritonealized pericolic or perirectal tissues via the muscularis propria. pT4a: The tumor perforates the visceral peritoneum. pT4b: The tumour immediately invades another organ or structure.
Regional lymph nodes. (N) pN0 indicates no regional lymph node metastasis. pN1a indicates metastases in one regional lymph node. pN1b refers to metastases in two or three regional lymph nodes. pN2a: metastases in 4-6 regional lymph nodes. pN2b: metastases in seven or more regional lymph nodes.
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