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Microsatellite instability in medullary breast carcinomas
F C Schmitt1, R Soares, H Gobbi
1Institute of Molecular Pathology and Immunology of the University of Porto, IPATIMUP, Porto, Portugal. fernando.schmitt@ipatimup.pt
International Journal of Cancer
|July 27, 1999
Summary
Microsatellite instability (MSI) is rare in medullary breast carcinoma (MBC), unlike in colorectal and gastric cancers. Genetic events in MBC differ from digestive tract tumors, despite shared features.
Area of Science:
- Oncology
- Genetics
- Cancer Research
Background:
- Microsatellite instability (MSI) is observed in various sporadic tumors, including colorectal and gastric cancers.
- MSI-positive tumors often present with lymphoid infiltration, poor differentiation, and a favorable patient outcome.
- Medullary breast carcinomas (MBCs) share clinico-pathologic features with MSI-positive tumors, prompting investigation into MSI in this breast cancer subtype.
Purpose of the Study:
- To evaluate the presence and frequency of microsatellite instability (MSI) in medullary breast carcinomas (MBCs).
- To investigate potential mutations in target genes (TGF-beta RII and BAX) associated with MSI in MBCs.
- To compare MSI characteristics of MBCs with those of MSI-positive colorectal and gastric carcinomas.
Main Methods:
- DNA extraction from 24 formalin-fixed, paraffin-embedded medullary breast carcinoma (MBC) tissues.
- Analysis of MSI using the BAT-26 marker.
- Screening for mutations in TGF-beta RII and BAX genes.
- Additional analysis of microsatellite markers (dinucleotide, tetranucleotide, pentanucleotide repeats) and loss of heterozygosity in a subset of cases.
Main Results:
- Microsatellite instability (MSI) was detected in 2 out of 24 (8.3%) MBC cases using the BAT-26 marker.
- No mutations were found in the TGF-beta RII and BAX genes in any of the analyzed MBC cases.
- No MSI was observed with the panel of tetra- and pentanucleotide markers; loss of heterozygosity was detected in some loci.
- The frequency of MSI in MBC is low, similar to other breast cancer types, and distinct from high MSI rates in colorectal and gastric cancers.
Conclusions:
- Medullary breast carcinomas (MBCs) exhibit a low frequency of microsatellite instability (MSI), comparable to other breast cancer subtypes.
- The genetic underpinnings of MBCs appear different from those of colorectal and gastric carcinomas, despite shared clinico-pathologic features.
- Further research is needed to elucidate the specific genetic events driving medullary breast carcinoma development.