Advertisement
Advertisement
Table of Contents
Definition / general | Essential features | Terminology | Epidemiology | Sites | Pathophysiology | Diagnosis | Prognostic factors | Case reports | Treatment | Clinical images | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Negative stains | Electron microscopy description | Molecular / cytogenetics description | Differential diagnosis | Additional referencesCite this page: Carcinoid - rectum. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/colontumorcarcinoid.html. Accessed July 14th, 2017.
Definition / general
- Well differentiated neuroendocrine tumor of rectum
- Usually low stage, with 5 year survival rate of 91% (World J Gastroenterol 2014;20:16252)
Essential features
- Most common carcinoid of colorectum
- Good prognosis overall, but larger tumors can behave aggressively
- Positive for neuroendocrine markers but also PSAP (a potential pitfall)
Terminology
- Proper term is "rectal well differentiated neuroendocrine tumor"
Epidemiology
- Annual incidence in USA: 10.6 per million (Int J Colorectal Dis 2007;22:183)
Sites
Pathophysiology
- Rare cases are familial (Tech Coloproctol 2006;10:143)
Diagnosis
- Half of cases are asymptomatic, discovered on colonoscopy (Dis Colon Rectum 1992;35:717)
Prognostic factors
- WHO grading, as for other neuroendocrine tumors, involves Ki67 proliferative index and mitotic rate
- Poor prognostic factors include higher stage, presence of lymphovascular invasion and size > 2 cm (Int J Colorectal Dis 2010;25:1087)
- Single most important predictor of outcome is ENETS / NANETS stage (Neuroendocrinology 2013;98:180)
- HES77 expression is also linked to worse prognosis (Anticancer Res 2015;35:3767)
Case reports
- 43 year old man with minute liver metastases (World J Gastrointest Surg 2010;2:89)
- 55 year old man with lifelong ulcerative colitis and atypical carcinoid (J Clin Pathol 1986;39:913)
- Woman with liver metastases from tumor % 0.5 cm (Hepatogastroenterology 2004;51:1330)
- Incidental finding on prostatic needle core biopsy (Hum Pathol 2010;41:1674)
Treatment
- Transanal endoscopic microsurgery usually is sufficient (J Laparoendosc Adv Surg Tech A 2006;16:435)
- Larger or high risk tumors may require surgery (Arch Surg 2008;143:471)
- Positive margins may not increase risk of recurrence (Am Surg 2011;77:198)
Clinical images
Images hosted on other servers:
Small rectal carcinoids on colonoscopy
Gross description
- Usually < 1 cm, round / polypoid, no ulceration
- May appear yellow or pale
Microscopic (histologic) description
- Islands, trabeculae, gland-like structures or sheets of monotonous neuroendocrine cells with amphophilic granular cytoplasm and round nuclei with "salt and pepper" chromatin
- Usually minimal pleomorphism and little to no mitotic activity
- Rarely mucin secretion or anaplasia; no necrosis
Microscopic (histologic) images
Images hosted on Pathout server - Contributed by Dr. Raul Gonzalez:
Small neuroendocrine tumor of the rectum
Synaptophysin positivity
Images hosted on other servers:
Rectal lesion
Small submucosal tumor
Rectal carcinoid and liver metastasis
Various images
Atypical carcinoid
Images hosted on Flickr:
Nested rectal carcinoid tumor
Chromogranin+ tumor
Positive stains
Negative stains
Electron microscopy description
- Cytoplasmic, well formed membrane bound secretory granules with dense (osmophilic) cores
Molecular / cytogenetics description
- Diploid if non metastasizing, aneuploid if metastatic
Differential diagnosis
- Prostatic adenocarcinoma: positive for PSA, negative for neuroendocrine markers
- Metastasis from other location: PAX8 is negative in ileal and pulmonary carcinoids, but positive in rectal carcinoid tumors
Additional references
Advertisement
