Mayo Test Catalog, (Sorted By Test Name) - Mayo Medical ...

MTBS
81507
microsatellite instability may also be valuable for clinical decision making. Colon cancers that
demonstrate defective DNA mismatch repair (MSI-H) have a significantly better prognosis compared to
those with intact mismatch repair (MSS/MSI-L). Additionally, current data indicate that stage II and
stage III patients with colon cancers characterized by the presence of defective MMR (MSI-H) may not
benefit from treatment with 5-FU alone or in combination with leucovorin (LV). These findings are
most likely to impact the management of patients with stage II disease.
Useful For: Evaluation of tumor tissue to identify patients at high risk for having hereditary
nonpolyposis colorectal cancer (HNPCC)/Lynch syndrome Note: Mayo's preferred screening test
(HNPCC/17073 Hereditary Nonpolyposis Colorectal Cancer [HNPCC] Screen) includes both
microsatellite instability (MSI) and Immunohistochemistry (IHC) testing. Evaluation of tumor tissue for
clinical decision making purposes given the prognostic implications associated with MSI phenotypes
Interpretation: The report will include specimen information, assay information, and interpretation of
test results. Microsatellite stable (MSS) is reported as MSS/MSI-L (0 or 1 of 5 markers demonstrating
instability) or MSI-H (2 or more of 5 markers demonstrating instability).
Reference Values:
An interpretive report will be provided.
Clinical References: 1. Baudhuin LM, Burgart LJ, Lentovich O, Thibodeau SN: Use of
microsatellite instability and immunohistochemistry testing for the identification of individuals at risk for
Lynch Syndrome. Fam Cancer 2005;4(3):255-265 2. Terdiman JP, Gum JR Jr, Conrad PG, et al: Efficient
detection of hereditary nonpolyposis colorectal cancer gene carriers by screening for tumor microsatellite
instability before germline genetic testing. Gastroenterology 2001 January;120(1):21-30 3. Popat S,
Hubner R, Houlston RS: Systematic review of microsatellite instability and colorectal cancer prognosis.
JCO 2005 23(3):609-618 4. Ribic CM, Sargent DJ, Moore MJ, et al: Tumor microsatellite-instability
status as a predictor of benefit from fluorouracil-based adjuvant chemotherapy for colon cancer. N Engl J
Med 2003 349:247-57
Microsporidia Stain
Clinical Information: Microsporidia are obligate protozoan parasites which have been documented
to infect invertebrates and vertebrates. They are very small organisms (1-2 microns, about the size of
bacteria) and are classified in a phylum, microspora, characterized by the structure of their spores which
contain polar tubules which are extruded to inject infective material into host cells. The microsporidia
known to infect humans include Enterocytozoon bieneusi (intestinal microsporidiosis), Encephalitozoon
hellem (eye infections), and Enterocytozoon (Septata) intestinalis (intestinal and disseminated infections,
especially to the biliary tree). Human infections have been reported most frequently in patients with
AIDS, but also can occur sporadically in immunocompetent patients. The primary clinical findings are
chronic diarrhea, weight loss, and malabsorption. Enterocytozoon bieneusi is found in the duodenal
mucosa and infection is accompanied by a wide spectrum of histopathologic changes ranging from normal
architecture to almost complete effacement of the villi and virtual obliteration of the lamina propria by
inflammatory cells. The anti-helmintic drug, albendazole has been found effective in some infections due
to Enterocytozoon bieneusi and Encephalitozoon (Septata) intestinalis.
Useful For: Diagnosis of intestinal microsporidiosis in patients with AIDS and others with unexplained
diarrhea, especially after overseas travel See Parasitic Investigation of Stool Specimens Algorithm in
Special Instructions for other diagnostic tests that may be of value in evaluating patients with diarrhea.
Interpretation: Presence of microsporidia in stool may or may not be associated with symptoms in
infected persons and may or may not be the cause of any symptoms since patients with AIDS may be
infected with more than 1 intestinal pathogen at the same time.
Reference Values:
Negative
If positive, reported as microsporidia
Clinical References: 1. Weber R, Bryan RT, Schwartz DA, Owen RL: Human microsporidial
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