DMBT1 expression distinguishes anorectal from cutaneous melanoma.
OBJECTIVE
Anorectal melanoma (AM) forms a rare but highly malignant subset of mucosal melanoma with an extremely poor prognosis. Although AMs display histological and immunohistochemical features very similar to cutaneous melanoma (CM), no association exists either with exposure to ultraviolet light or with melanocytic naevi. While AMs are clearly distinguished from CM by displaying few BRAF mutations, they are commonly indistinguishable from CM at the level of gene expression. The aim was to carry out expression analyses of classical immunohistochemical markers and of the protein deleted in malignant brain tumours 1 (DMBT1) in cases of primary anorectal malignant melanoma and CM.


RESULTS
Expression analyses of classical immunohistochemical markers (S100, HMB45, Melan A and MiTF) and of the protein DMBT1 were carried out in 27 cases of primary anorectal malignant melanoma and 26 cases of CM. All AM cases analysed showed expression of at least three of the classical markers for melanoma. However, immunohistochemistry showed 19 out of 27 AM to be positive for DMBT1, which represented a statistically significant difference (P = 0.0009) compared with CM (six out of 26), which more commonly are negative for DMBT1 expression.


CONCLUSIONS
These results identify DMBT1 as a molecular feature that may allow distinction between AM and CM and support the notion that AM represents an entity molecularly distinct from CM.
Helmke
Burkhard Maria
BM
Institute of Pathology, University of Heidelberg, Heidelberg, Germany. burkhard.helmke@elbekliniken.de
Renner
Marcus
M
Poustka
Annemarie
A
Schirmacher
Peter
P
Mollenhauer
Jan
J
Kern
Michael André
MA
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001005:Anus Neoplasms / Q000175:diagnosis* / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000032:analysis*; D002135:Calcium-Binding Proteins; D004268:DNA-Binding Proteins; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008545:Melanoma / Q000175:diagnosis* / Q000378:metabolism; D008875:Middle Aged; D011956:Receptors, Cell Surface / Q000096:biosynthesis*; D012878:Skin Neoplasms / Q000175:diagnosis* / Q000378:metabolism; D025521:Tumor Suppressor Proteins
D014408:Biomarkers, Tumor; D002135:Calcium-Binding Proteins; C108174:DMBT1 protein, human; D004268:DNA-Binding Proteins; D011956:Receptors, Cell Surface; D025521:Tumor Suppressor Proteins