Monthly Archives: August 2010

Gastrointestinal Stromal Tumor

Gastrointestinal Stromal Tumors

GIST

Classification

– very low, low, intermediate and high risk of aggressive behavior

Microscopic Appearance

-  spindle and epithelioid types

Immunohistochemistry

– CD117+ in 90%, CD34 + in 70%, SMA can  be focally positive, desmin – ( positive in leiomoyomas)

Histogenesis

-can arise anywhere in the GI tract; 60-70% from stomach, 20-30% from the SI and <10% from the rest

-proliferation of the interstitial cells of Cajal

-association with c-kit and PDGFA genes -  these are receptors with tyrosine kinase intracellular domains, and mutation causes their constitutive activation with activation of downstream signaling, leading to cell proliferation.

Differential Diagnosis

-leiomyomas

-leiomyosarcomas

-inflammatory fibroid polyp

-fibromatosis

-schwannoma

-inflammatory myofibrobastic tumor

-solitary fibrous tumor

Reporting

- report size, morphologic type, mitotic count per 50 HPFs , cellular atypia, presence of any necrosis

MIB count has been found to be correlative with prognosis:

0-9%  low, 10-29% intermediate, 30% or higher – high risk.

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Lower Small Intestine Obstruction

Lower Small Intestine Obstruction

Causes

-post-operation adhesions
-malignancy
-Crohn’s
-hernias

Classification

-partial or complete
-strangulated  (surgical emergency – leads to bowel ischemia) or non-strangulated

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Ovarian Primary

Ovarian Primary

Features ( clinical gross micro or immunohistochemistry ) that differentiate primary ovarian cancer form colorectal metastasis to the ovary

Ovarian primary favored if:

No colon mass
Unilateral ovarian involvement
Single >5mm  ( as opposed to multiple lesions <5mm)  lesion
Certain morphologies – like serous – favor the ovarian origin
Pre-malignant lesion such as serous LMP adjacent to carcinoma
Lesions associated with certain ovarian malignancies  – ie. endometriosis is associated with clear cell carcinoma, endometrioid carcinoma, carcinosarcoma MMMT, endocervical variant of mucinous LMP.

Ovarian neoplasms are typically  CK7+, CK20 – , except for mucinous carcinomas with can be CK20 +
WT-1 helpful with ovarian serous carcinoma

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Colon Cancer Prognostic Factors

Prognostic factors

-size
-depth of invasion
-lymph node status

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Colon Cancer Risk Factors

Colon Cancer Risk Factors

Risk factors with high incidence

-age
-Ulcerative Colitis
-Crohn’s Disease
-FAP
-HNPCC

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Blind Loop Syndrome

Blind  Loop Syndrome

Stasis syndrome or stagnant loop syndrome

Definition

-a condition in which part of the small intestine is bypassed and cut off from the normal flow of food and digestive juices. Bacterial overgrowth results, interfering with  absorption of essential nutrients, often leading to diarrhea, weight loss and malnutrition.

Causes

- structural defect in or an injury to your small intestine – surgery  such as Billroth II or Roux-en-Y, gastric bypass

-Crohn’s disease, intestinal lymphoma, scleroderma or diabetes  – slowed transit time through intestine

-Diverticulosis of the small intestine

Presentation

Loss of appetite

Abdominal pain

Nausea

Fatty stools (steatorrhea) — frothy, foul-smelling stools indicating poor fat absorption

Bloating

An uncomfortable feeling of fullness after eating

Diarrhea

Unintentional weight loss

Complications

-abnormalites in normal bacterial flora cause poor deconjugation of bile salts, which are required for fat emulsification and digestion. Resultant steatorrhea and malabsorption of fat-soluble vitamins -  ADEK

-damage to intestinal mucosa -  malabsorption of most other nutrients

-B12 malabsorption

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Solitary rectal ulcer syndrome

Solitary rectal ulcer syndrome and Mucosal Prolapse

Cause

-malfunction of the puborectalis muscle such that excessive straining on defecation results. This leads to mucosal prolapse that ultimately may ulcerate and form polypoid masses.
-prolapse polyps also occur in association with diverticular disease, at ostomy sites and adjacent to mass lesions.
- mucosal prolapse occurs at the anal verge, and forms a polyp – inflammatory cloacogenic polyp

Symptoms

-    alternating diarrhea and constipation,
-    pain and difficulty defecating
-    rectal bleeding

Gross Appearance

- friable ulcerated polyps/ masses on the anterior rectal wall or at  mouths of diverticula or stomas

Microscopic Appearance

-fibromuscular hyperplasia of the LP
-hyperplastic regenerative epithelium
-crypt distortion
-surface ulceration
-submucosal entrapment of crypts filled with mucin – colitis cystica profunda

 Prognosis

-responds well to bulk laxatives and stool softeners, may require retropexy or resection

Syndromes associated with mucosal prolapse:

Solitary rectal ulcer syndrome
Inflammatory cloacogenic polyp
Colitis cystica profunda

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Lymphocytic Colitis

Lymphocytic Colitis

Microscopic Colitis

Clinical

-all ages, M=F

-cause unknown

-prolonged watery diarrhea

-associated with autoimmune disease in some patients (celiac sprue, arthritis and thyroiditis)

-normal colonoscopic exam

Microscopic Appearance

-generally involves the entire colon

-marked increase in lymphocytes in the surface and crypt epithelium

-absence of thickened subepithelial collagen layer

-chronic inflammation in the lamina propria

-no crypt distortion

-may have occasional foci of cryptitis or neutrophils in the surface epithelium

Differential Diagnosis

-collagenous colitis

-resolving infectious colitis

-chronic epithelial lymphocytosis associated with food or water-borne epidemics

-Crohn’s disease

-normal mucosa overlying a lymphoid aggregate

-lymphocytic enterocolits

** Always check the clinical history before making the diagnosis.

Prognosis

-most patients respond to symptomatic or antiinflammtory therapy. Those who don’t respond  tend to also have sprue-like symptom may be classified as having  lymphocytic enterocolitis

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Collagenous Colitis

Collagenous Colitis

Microscopic Colitis

Clinical

-middle –aged and older women, M:F= 1:10

-protracted watery diarrhea without systemic symptoms

-normal colonoscopic exam

Microscopic Appearance

-proximal colon more affected

-thickened subepithelial collagen  layer usually >10uM (normal 2-3), best viewed by Masson trichrome, collagen also encircles the superficial capillaries

-chronic inflammation in the lamina propria

-no crypt distortion

-may have occasional foci of cryptitis or neutrophils in the surface epithelium

Differential Diagnosis

-lymphocytic colitis

-radiation colitis

-infectious colitis

-mucosal prolapse/SRUS

-ulcerative colitis

-chron’s

-normal mucosa with thick basement membrane

-enema effect

Prognosis

-most patients respond to symptomatic or anti-inflammtory therapy.

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Meckel’s Diverticulum

Meckel’s Diverticulum

- derived from the omphalomesenteric or vitelline  duct  – a true diverticulum  which involves all layers of the intestinal wall

-most common malformation of the GI tract

-true diverticulum MUST include all three layers of the GI tract

Meckel’s Diverticulum rule of 2′s:

-2% (of the population)

- 2 feet (from the ileocecal valve)

- 2 inches (in length)

- 2% are symptomatic,

2 types of common ectopic tissue (gastric and pancreatic)

-the most common age at clinical presentation is 2

-males are 2 times as likely to be affected.
-Can present as intussusception, incarceration and perforation.

-the ectopic gastric tissue can cause peptic ulceration of the surrounding ileal mucosa

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