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Tag Archives: microsatellite instability
Colon Medullary Adenocarcinoma
Colon Medullary Adenocarcinoma
Also known as undifferentiated carcinoma of the colon
Pathophysiology: strongly associated with microsatellite instability MSI-H and no or few nodal metastases
- sporadic or associated with hereditary non-polyposis colorectal carcinoma syndrome HNPCC
Gross: large size with invasion into adjacent organs
Histology: expansive sheets of cells
- no/minimal mucin production,
- no tubules formation
- lymphocytic infiltration
- cells:uniform, polygonal to round, nucleoli, mitoses
Immunohistochemistry (IHC)
Positive IHC: CK, CEA, EMA
Negative IHC: neuroendocrine markers, MLH1, MSH2
Posted in Colon
Tagged Colon, Colon Medullary Adenocarcinoma, Colon undifferentiated carcinoma, medullary adenocarcinoma, Medullary adenocarcinoma immunohistochemistry, Medullary adenocarcinoma of the colon, Medullary cancer, medullary carcinoma, Medullary carcinoma immunohistochemistry, microsatellite instability, Microsatellite instability pathway, Undifferentiated carcinoma
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Hereditary Non-Polyposis Colorectal Cancer Syndrome
Hereditary Non-Polyposis Colorectal Cancer Syndrome
Clinical: earlier onset of cancer , ~ 45 years
Genetics:
- mutation in DNA mismatch repair genes: hMLH1, hMSH2,
hPMS1/2
- results in MSI (expansion or contraction)
- microsatellite: tandem repeats of 1-4 nucleotides
Extracolonic lesions:
Cholangiocarcinoma
Endometrial carcinoma
Ovarian cancer
Amsterdam and Bethesda criteria:
- family history of colorectal cancer
- previous relative with colorectal cancer less than 50 years
Histology
- more likely to have right-sided colonic lesions
- more poorly differentiated
- lymphocytic infiltration
- mucinous differentiation
- no dirty necrosis
Immunohistochemistry
- hMLH1, hMSH2 loss of staining suggests mutation in gene with additional DNA testing for MSI expansion, contraction
Posted in Colon
Tagged Cholangiocarcinoma, DNA mismatch repair genes, endometrial carcinoma, Hereditary Non-Polyposis Colorectal Cancer Syndrome, hMLH1, hMSH2, hnpcc, hPMS1/2, microsatellite instability, MSI, MSI instability, ovarian cancer
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Hereditary Nonpolyposis Colorectal Cancer Syndrome
Hereditary Nonpolyposis Colorectal Cancer (HNPCC) Syndrome
Hereditary Nonpolyposis Colorectal Cancer (HNPCC) Syndrome, also known as Lynch syndrome, is a rare colorectal syndrome that can lead to cancer of the colon.
Hereditary Nonpolyposis Colorectal Cancer Syndrome Inheritance pattern
- autosomal dominant
- syndromal patients have only one functional allele and cancer occurs through loss of heterozygosity (LOH)
- mutations occur in mismatch repair genes (MLH1, MSH 2, MSH6, PMS 1, PMS 2)
- mutations lead to microsatellite instability which are mostly repeats in intronic regions
What to look for?
- you can look for the loss of the genes themselves
- you can look at particular microsatellite loci and see how many have instability
- 0/5 – stable
- 1/5 – low frequency instability
- 2 or greater/5 – high frequency of instability – MSI-H
- microsatellite instability is NOT specific to HNPCC, as it is seen in 10-15 % of sporadic colorectal carcinomas. Sporadic tumors arise in older patients who lack a family history. The activity of the mismatch repair genes in sporadic tumors is lost through hypermethylation
Diagnostic criteria is through the Amsterdam II criteria
Clinical presentation
- development of multiple cancers at an early age, including cancer of the colon, endometrium, renal pelvis and ureter, small bowel, ovary, brain, hepatobiliary tract and sebaceous tumors
Muir -Torre Syndrome
- sebaceous tumors along with HNPCC type of internal malignancy
Turcot Syndrome
- tumors of the CNS (usually gliobalstomas) and multiple colorectal tumors
Gross Appearance
- predilection for right colon and cecum all the way to the transverse colon
- usually polypoid in appearnace rather than diffuse
Microscopic Appearance
- sporadic tumors have the same features as tumors associated with HNPCC
- proximally located mucinous type of colorectal adenocarcinomas +/- tumor infiltrating lymphocytes
- proximally located, poorly differentiated medullary or undifferentiated colorectal adenocarcinomas – these are well circumscribed and lacking abundant desmoplastic stroma and may contain tumor infiltrating lymphocytes
- adenomas – many have a villous morphology and high grade dysplasia, with rapid progression to carcinoma
Posted in Colon, GI, Syndrome
Tagged , gross, Hereditary Nonpolyposis Colorectal Cancer Syndrome, hnpcc, loss of heterozygosity, lynch syndrome, medullary adenocarcinoma, microsatellite instability, microscopic, mismatch repair genes, mlh, mucinous adenocarcinoma, muir-torre syndrome, multiple cancers, mutations, right colon, Syndrome, turcot syndrome
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