DNA mismatch repair protein expression and microsatellite instability in primary mucosal melanomas of the head and neck.
OBJECTIVE
To examine the expression of DNA mismatch repair (MMR) proteins and the presence of microsatellite instability (MSI) in seven primary mucosal melanomas of the head and neck (MMHN).


RESULTS
Haematoxylin and eosin staining and immunohistochemical analysis for routine diagnostic markers and for MMR proteins were performed. Six cases were examined for MSI. Four cases were monomorphous and three cases were pleomorphic type MMHN. Melanocytic markers were positive in all cases. Immunoreactivity for MMR proteins was weak in normal epithelium. The neoplastic tissue in six cases showed positivity for all MMR proteins with different percentages. One case showed weak positivity for hMSH2 and hMSH6 and no immunoreactivity for hMLH1 or hPMS2. Staining intensity was higher in tumour cells than in matched normal mucosa in three cases for hMSH2 and hMLH1 and in two cases for hPMS2. None of the examined cases showed MSI.


CONCLUSIONS
Expression of hMSH2 and hMLH1 proteins was up-regulated in three cases, whereas in two cases that of hPMS2 was increased. hMSH6 expression was comparable to that of normal cells in all cases. The percentage of positive neoplastic cells and the intensity of staining seemed to be greater in pleomorphic melanomas. Six cases were MMR-proficient and microsatellite stable.
Marani
C
C
Department of Pathology, Ospedale San Carlo-IDI IRCCS, Via Aurelia 275, 00165 Rome, Italy.
Alvino
E
E
Caporali
S
S
Vigili
M G
MG
Mancini
G
G
Rahimi
S
S
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D000368:Aged; D000369:Aged, 80 and over; D053843:DNA Mismatch Repair; D045643:DNA Repair Enzymes / Q000235:genetics / Q000378:metabolism; D004273:DNA, Neoplasm / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism / Q000473:pathology; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006258:Head and Neck Neoplasms / Q000175:diagnosis / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008297:Male; D008545:Melanoma / Q000175:diagnosis / Q000235:genetics* / Q000378:metabolism; D053842:Microsatellite Instability; D008875:Middle Aged; D000070976:Mismatch Repair Endonuclease PMS2; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation
D048868:Adaptor Proteins, Signal Transducing; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; C094443:G-T mismatch-binding protein; C501486:MLH1 protein, human; D009687:Nuclear Proteins; D000251:Adenosine Triphosphatases; C094934:PMS2 protein, human; C497172:MSH2 protein, human; D000070976:Mismatch Repair Endonuclease PMS2; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D045643:DNA Repair Enzymes