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Pathology - Colorectal polyps
Hyperplastic polyps are prevalent, predominantly found in the distal colon. • Typically little lesions, less than 1 cm in size, located on the apex of a mucosal fold. Microscopically, they consist of crypts that are dilated and serrated in the superficial region and constricted at the base. • Benign lesions devoid of any potential for development to malignancy. Adenomatous polyps • Prevalent polyps that can manifest throughout the large intestine. • They predominantly manifest sporadically, although are also linked to familial adenomatous polyposis (FAP).
Familial Adenomatous Polyposis (FAP) is a hereditary disorder characterized by the proliferation of many adenomas throughout the colon at an early age, leading to the unavoidable onset of colorectal cancer in the absence of preventive colectomy.
• Neoplastic polyps that contain prevalent mutations of APC, KRAS, and TP53. The polyps exhibit dysplastic glands, characterized by epithelial cells with stratified hyperchromatic nuclei, arranged in intricate tubules or finger-like villous extensions. The dysplasia is classified as low grade or high grade based on the extent of cytological and architectural abnormalities. Approximately 10% of adenomas progress to cancer. The probability of malignant transformation increases with larger polyps, high-grade dysplasia, and a villous architecture.
Sessile serrated adenomas • Recently identified polyps that are often greater than 1 cm and are more frequently located in the right colon. • Genetically, they typically possess mutations in mismatch repair genes. • Microscopically, they exhibit significantly dilated serrated crypts that are broadened at their base. • Correlated with a heightened risk of subsequent colorectal cancer.
Inflammatory polyps • Delicate filiform lesions arise subsequent to any mucosal injury, frequently observed in individuals with inflammatory bowel illness. • Microscopically, they are enveloped by mucosa on both sides, with minimal submucosal tissue present.
Mucosal prolapse • Prolapsed mucosal fragments manifesting as polypoid projections. • May manifest at any location within the large intestine, but is typically observed on the anterior rectal wall or in conjunction with diverticular illness. • May ulcerate and resemble colorectal malignancy. • Microscopically, they have deformed, angulated crypts embedded inside a lamina propria that contains bundles of smooth muscle.
Benign fibroblastic polyps are typically discovered during screening colonoscopy in adults. They appear as bland spindle cell growth in the lamina propria under a microscope. Immunohistochemistry analysis does not reveal a distinct differentiation line for spindle cells.
Leiomyomas are benign smooth muscle tumors that originate from the muscularis mucosae. They are often tiny polyps seen in the distal large bowel and exhibit bland smooth muscle cell bundles under the microscope.
Juvenile polyps • The most frequent colonic polyp in children. • Identified as hamartomatous. • Microscopically, they have dilated and disordered colonic glands in an oedematous stroma. Multiple juvenile polyps may indicate juvenile polyposis, an autosomal dominant disorder caused by germline mutations in SMAD4 or BMPR1A.
Hyperplastic polyps are prevalent, predominantly found in the distal colon. • Typically little lesions, less than 1 cm in size, located on the apex of a mucosal fold. Microscopically, they consist of crypts that are dilated and serrated in the superficial region and constricted at the base. • Benign lesions devoid of any potential for development to malignancy. Adenomatous polyps • Prevalent polyps that can manifest throughout the large intestine. • They predominantly manifest sporadically, although are also linked to familial adenomatous polyposis (FAP).
Familial Adenomatous Polyposis (FAP) is a hereditary disorder characterized by the proliferation of many adenomas throughout the colon at an early age, leading to the unavoidable onset of colorectal cancer in the absence of preventive colectomy.
• Neoplastic polyps that contain prevalent mutations of APC, KRAS, and TP53. The polyps exhibit dysplastic glands, characterized by epithelial cells with stratified hyperchromatic nuclei, arranged in intricate tubules or finger-like villous extensions. The dysplasia is classified as low grade or high grade based on the extent of cytological and architectural abnormalities. Approximately 10% of adenomas progress to cancer. The probability of malignant transformation increases with larger polyps, high-grade dysplasia, and a villous architecture.
Sessile serrated adenomas • Recently identified polyps that are often greater than 1 cm and are more frequently located in the right colon. • Genetically, they typically possess mutations in mismatch repair genes. • Microscopically, they exhibit significantly dilated serrated crypts that are broadened at their base. • Correlated with a heightened risk of subsequent colorectal cancer.
Inflammatory polyps • Delicate filiform lesions arise subsequent to any mucosal injury, frequently observed in individuals with inflammatory bowel illness. • Microscopically, they are enveloped by mucosa on both sides, with minimal submucosal tissue present.
Mucosal prolapse • Prolapsed mucosal fragments manifesting as polypoid projections. • May manifest at any location within the large intestine, but is typically observed on the anterior rectal wall or in conjunction with diverticular illness. • May ulcerate and resemble colorectal malignancy. • Microscopically, they have deformed, angulated crypts embedded inside a lamina propria that contains bundles of smooth muscle.
Benign fibroblastic polyps are typically discovered during screening colonoscopy in adults. They appear as bland spindle cell growth in the lamina propria under a microscope. Immunohistochemistry analysis does not reveal a distinct differentiation line for spindle cells.
Leiomyomas are benign smooth muscle tumors that originate from the muscularis mucosae. They are often tiny polyps seen in the distal large bowel and exhibit bland smooth muscle cell bundles under the microscope.
Juvenile polyps • The most frequent colonic polyp in children. • Identified as hamartomatous. • Microscopically, they have dilated and disordered colonic glands in an oedematous stroma. Multiple juvenile polyps may indicate juvenile polyposis, an autosomal dominant disorder caused by germline mutations in SMAD4 or BMPR1A.
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