Small intestine
The small intestine, also small bowel, is a relatively well-behaved piece of machinery from the perspective of pathology. It is uncommonly affected by malignancies, relative to its length when compared to the colon and rectum.
Normal small bowel
- AKA normal small intestine.
Anatomy
Consists of three segments:
- Duodenum - can be divided into four parts.
- Jejunum.
- Ileum.
The later two parts keep general surgeons awake at night (quite literally) 'cause they get obstructed and need urgent operations.
Histology
Main article: Gastrointestinal pathology
The Gastrointestinal pathology article covers basic histology of the GI tract.
Immunohistochemistry
- Normal small intestine is CK20 +ve... while adenocarcinoma of the small bowel may be CK20 -ve.[1]
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SMALL BOWEL, BIOPSY: - SMALL BOWEL MUCOSA WITHIN NORMAL LIMITS.
TERMINAL ILEUM, BIOPSY: - SMALL BOWEL MUCOSA WITHIN NORMAL LIMITS.
The segments
Duodenum
Main article: Duodenum
The duodenum is often biopsied by gastroenterologists.
Common reasons for biopsy:
- Suspected giardia.
- Suspected celiac sprue.
- Is this cancer?
- Looks normal... want to dot the i's and cross the t's.
Jejunum
- Uncommonly seen by pathologists.
- May be seen in the context of a resection done for a bowel obstruction.
Ileum
- This is seen occasionally -- often in the context of IBD and more specifically Crohn's disease.
- Crohn's disease (and ulcerative colitis) is discussed in the colon article.
Specific conditions
Small bowel obstruction
- Abbreviated SBO.
General
- Radiologic/clinical diagnosis.
The usual causes of bowel obstruction (large & small) are (mnemonic) SHAVING:
- Adhesions > hernias > neoplasms.
In the context of bowel obstructions and IBD, pathologists often see resected stomas (that were put in place emergently). These specimens are usually fairly straight forward.
Radiology
- Air-fluid levels.
Gross
- +/-Adhesions.
- +/-Bowel contorted.
- +/-Luminal narrowing +/-proximal dilation.
- +/-Serosal exudate.
- Suggestive of perforation.
Microscopic
Features:
- +/-Adhesions (serosal).
- Dense fibrous tissue replaces the adipose tissue.
- +/-Increased vascularity.
- +/-Submucosal fibrosis.
- +/-Serositis - seen in small bowel perforation.
DDx:
- Small bowel adenocarcinoma - most important differential diagnosis.
- Metastatic adenocarcinoma - classically on the serosal aspect.
- Signet ring cell carcinoma.
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SMALL BOWEL, RESECTION: - SMALL BOWEL WITH FIBROUS ADHESIONS (EXTENSIVE) AND FOCAL LUMINAL NARROWING. - NEGATIVE FOR DYSPLASIA AND NEGATIVE FOR MALIGNANCY.
SMALL BOWEL, RESECTION: - SMALL BOWEL WITH FIBROUS ADHESIONS (EXTENSIVE), FOCAL LUMINAL NARROWING AND A FOREIGN BODY-TYPE GRANULOMA. - NEGATIVE FOR DYSPLASIA AND NEGATIVE FOR MALIGNANCY.
Small bowel neoplasms
- Adenocarcinoma - like colonic.
- Adenosquamous carcinoma.
- Neuroendocrine tumour.
- GIST.
- Schwannoma.
- Classically have a peripheral lymphoid cuff.[4]
Ileal nodular lymphoid hyperplasia
- AKA nodular lymphoid hyperplasia of the terminal ileum.
General
- An uncommon diagnosis.
- May be associated with hypogammaglobulinemia.[5]
Gross
- Mucosal nodularity.
Microscopic
Features:
- Lymphoid nodules +/- germinal centre formation.
DDx:
- MALT lymphoma.
- Mantle cell lymphoma.
- Other lymphomas.
IHC
- CD20 and CD3 - mixed population of lymphocytes.
- CD23 - follicular dendritic cells.
- Cyclin D1 -ve.
Note:
- IHC should be used if there is:
- Clinical suspicion.
- Histologic suspicion - either:
- Sheets of lymphocytes without apparent germinal centre formation in a larger area (~ 2 mm).
- Lymphoepithelial lesions.
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TERMINAL ILEUM, BIOPSY: - SMALL BOWEL MUCOSA WITH LYMPHOID NODULES WITH GERMINAL CENTRE FORMATION -- NO SIGNIFICANT PATHOLOGY. - NEGATIVE FOR ILEITIS.
TERMINAL ILEUM, BIOPSY: - SMALL BOWEL MUCOSA WITH LYMPHOID HYPERPLASIA -- NO SIGNIFICANT PATHOLOGY.
Micro
The sections show small bowel mucosa with lymphoid hyperplasia.
Immunostains for CD3, CD20 show a mixed population of lymphocytes. CD23 show follicular dendritic cells. Cyclin D1 is negative.
Multiple lymphomatous polyposis
- Abbreviated MLP.
- AKA lymphomatous polyposis.
General
- MLP is classically due to mantle cell lymphoma.[6]
- May be due to other lymphomas, e.g. follicular lymphoma.[7]
Microscopic
Features:
- Lymphoid nodules consisting of (small) atypical lymphocytes with an abnormal architecture.
IHC
See small cell lymphomas.
Small bowel diaphragm disease
- AKA diaphragm disease.
General
Microscopic
Features:[8]
- Focal submucosal fibrosis.
- +/-Distortion of adjacent muscularis propria.
- +/-Adjacent mucosal erosions/granulation tissue.
DDx:
Meckel diverticulum
General
- Most common congenital anomaly of the gastrointestinal tract.[9]
- Remnant of the omphalomesenteric duct - a connection of the yolk sac and midgut.
The rule of 2s:
- 2 feet from the terminal ileum
- 2% of the population
- 2% symptomatic.
- 2 inches long.
- 2 year old.
- 2 types of epithelium - gastric and pancreatic.
Main clinical DDx of a symptomatic Meckel diverticulum:
Gross
- Antimesenteric attachement, i.e. a Meckel's diverticulum hangs off the side opposite of the mesentery.
Image:
Microscopic
Features:[9]
- Small bowel mucosa.
- +/-Gastric mucosa:
- Foveolar epithelium: champagne flute-like columnar epithelium.
- Oxyntic mucosa: parietal cells (pink) and chief cells (purple).
- +/-Pancreatic epithelium:
- Pancreatic acini.
Images:
- Gastric foveolar epithelium in a MD (radiographics.rsna.org).
- Gastric glands in a MD (radiographics.rsna.org).
- Pancreatic glands in a MD (radiographics.rsna.org).
Ischemic enteritis
General
- Typically elderly and due to atherosclerosis.
- Rare.
- High mortality.[10]
- May occur together with ischemia of the colon, i.e. ischemic colitis, in which case it is known as ischemic enterocolitis.
Etiologies:
- Atherosclerosis.
- Vasculitis.
- Embolism.
- Thrombosis.
Microscopic
Features:
- See ischemic colitis.
DDx:
- Infection.
- Crohn's disease.
- Radiation changes.
- Drugs/toxins.
Weird stuff
Autoimmune enteropathy
- Abbreviated as AIE.
General
- Considered a pediatric disease.
- Super rare in adults - there are only ~11 reported cases in the literature.[11]
Diagnosis is clinico-pathologic:[11]
- Intact immune system.
- Autoantibodies.
- Anti-enterocyte antibody.
- Anti-goblet antibody.
- Lack of response to gluten-free diet.
Microscopic
Features:[11]
- +/-Loss of goblet cells.
- +/-Loss of paneth cells.
- Villous blunting.
DDx:
See also
References
- ↑ Chen ZM, Wang HL (October 2004). "Alteration of cytokeratin 7 and cytokeratin 20 expression profile is uniquely associated with tumorigenesis of primary adenocarcinoma of the small intestine". Am. J. Surg. Pathol. 28 (10): 1352–9. PMID 15371952.
- ↑ URL: http://www.emedicine.com/EMERG/topic66.htm. Accessed on: 19 April 2011.
- ↑ TN 2007 GS21
- ↑ Levy AD, Quiles AM, Miettinen M, Sobin LH (March 2005). "Gastrointestinal schwannomas: CT features with clinicopathologic correlation". AJR Am J Roentgenol 184 (3): 797–802. PMID 15728600. http://www.ajronline.org/cgi/content/full/184/3/797.
- ↑ Yamaue H, Tanimura H, Ishimoto K, Morikawa Y, Kakudo K (1996). "Nodular lymphoid hyperplasia of the terminal ileum: report of a case and the findings of an immunological analysis". Surg. Today 26 (6): 431-4. PMID 8782302.
- ↑ Ruskoné-Fourmestraux, A.; Audouin, J. (Feb 2010). "Primary gastrointestinal tract mantle cell lymphoma as multiple lymphomatous polyposis.". Best Pract Res Clin Gastroenterol 24 (1): 35-42. doi:10.1016/j.bpg.2009.12.001. PMID 20206107.
- ↑ URL: http://www.pathmax.com/gilymph.html. Accessed on: 1 April 2012.
- ↑ 8.0 8.1 McCune KH, Allen D, Cranley B (October 1992). "Small bowel diaphragm disease--strictures associated with non-steroidal anti-inflammatory drugs". Ulster Med J 61 (2): 182–4. PMC 2448949. PMID 1481311. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2448949/.
- ↑ 9.0 9.1 Levy, AD.; Hobbs, CM.. "From the archives of the AFIP. Meckel diverticulum: radiologic features with pathologic Correlation.". Radiographics 24 (2): 565-87. doi:10.1148/rg.242035187. PMID 15026601.
- ↑ Nakase, H. (Jul 2008). "[Ischemic enteritis].". Nihon Rinsho 66 (7): 1330-4. PMID 18616124.
- ↑ 11.0 11.1 11.2 Akram, S.; Murray, JA.; Pardi, DS.; Alexander, GL.; Schaffner, JA.; Russo, PA.; Abraham, SC. (Nov 2007). "Adult autoimmune enteropathy: Mayo Clinic Rochester experience.". Clin Gastroenterol Hepatol 5 (11): 1282-90; quiz 1245. doi:10.1016/j.cgh.2007.05.013. PMC 2128725. PMID 17683994. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2128725/.