Small Intestine - Diagnostic Pathology GI Flashcards
Enteric duplication cyst
Very rare congenital anomaly. Thought to arise from abnormal bowel recanalization.
Muscular cyst with all the layers of the intesitnal tract – unlike an enterogenous cyst, which will not have nerves or ganglion and will display more disorganized muscle.
Rarely, may present with perforation.
Meckel’s diverticulum rule of 2’s
Symptoms before age 2
Located 2 feet from the ileocecal valve
2 inches long
Seen in ~2% of the population
Scan for Meckel’s diverticulum
Technetium 99m pertechnetate
Will show a hot spot in the RLQ
Gastric heterotopia
Gastric mucosa occuring outside of the stomach, not including Meckel’s diverticulum.
About ~2% of people have some in the duodenum, although they can appear anywhere from the oral cavity to the anal canal.
Ectopic pancreas / pancreatic heterotopia
Generally an asymptomatic, incidental finding
May develop pancreatic exocrine or endocrine malignancies, OR may develop pancreatitis and subsequent pseudocyst.
Often presents on EGD as “a small intramural gastric mass with central umbilication.” Can appear anywhere in the upper GI tract.
Adenomyomayous hyperplasia of the ampulla of Vater
Extremely rare tumor of the biliary tree.
Unlike in other organs, this location has important clinical consequences, being misdiagnosed as an adenoma or carcinoma in most cases.
Tests for suspected MVID on histology
PAS stain will show granular stianing of the apical enterocyte cytoplasm (shown).
Villin and CD10 will highlight intracytoplasmic subapical vacuoles.
Electron microscopy will demonstrate intracytoplamic vacuoles.
Lymphangiectasia on gross
Course w/ chronic lymphedema, costant proteinaceous diarrhea with hypoalbuminemia (gastrosis), and fat-soluble vitamin deficiencies.
On histology, you will see dilated lacteals within the villi (shown).
May be associated with autoimmune polyglandular syndrome type-1, caused by mutations in AIRE.
Gastric mucosa in the duodenum means. . .
Either gastric heterotopia or peptic duodenitis
Gastric mucosa in the terminal ileum means. . .
Pyloric metaplasia
Common in Crohn’s disease
Mycobacterium avium complex in the intestinal tract
Presents as infiltration of intestinal villi by histiocytes – but without granuloma formation.
When present, often present in both small and large bowel.
Disseminated MAC infection of the GI tract is common in AIDS patients.
PAS/AB or Ziehl-Neelsen stains highlight the acid fast bacteria within the macrophages (shown).
Whipple’s disease in the intestinal tract
Like MAC, presents as foamy macrophages within the lamina propria.
Also like MAC, you will stain with periodic acid schiff/alcian blue. But, the result will be diffuse and strong PAS positivity compared to a more focal intracellular positivity in MAC.
Usually involves the postbulbar duodenum and jejunum.
Apoptotic enterocolitis DDx
- GVHD
- ICI-related colitis
- CMV
- Adenovirus
- Mycophenolate or other antimetabolite
- Autoimmune enteropathy (idiopathic)
- Common variable immunodeficiency
Marsh score for Celiac’s disease (focusing on Marsh III variants)
Marsh 0: Less than 25 IELs per 100 enterocytes, normal crypts, normal villi
Marsh I: >25 IELs per 100 enterocytes, normal crypts, normal villi
Marsh II: >25 IELs per 100 enterocytes, crypt hyperplasia, normal villi
Marsh IIIa: >25 IELs per 100 enterocytes, crypt hyperplasia, mild/partial villous atrophy (branching villi, slightly shorter)
Marsh IIIb: >25 IELs per 100 enterocytes, crypt hyperplasia, moderate/subtotal villous atrophy (some architectural abnormality, slightly shorter, mildly expanded by lymphocytic infiltrate)
Marsh IIIc: >25 IELs per 100 enterocytes, crypt hyperplasia, severe/total villous atrophy (classical villous blunting with large increase in chronic inflammatory cells)
Marsh IV: Hypoplastic/atrophic small bowel architecture (villi basically gone, flat colon-like epithelium)
