Differences in sialyl-Tn antigen expression between keratoacanthomas and cutaneous squamous cell carcinomas

Area of Science:

• Dermatology
• Oncology
• Immunology

Background:

• Keratoacanthoma (KA) and cutaneous squamous cell carcinoma (cSCC) are common skin tumors, often challenging to differentiate, particularly in immunosuppressed transplant recipients.
• Sialyl-Tn (Sia-GalNAc-O-Ser/Thr) is a cell surface carbohydrate linked to squamous epithelial hyperplasia and poor prognosis in some adenocarcinomas.

Purpose of the Study:

• To investigate and compare the expression of Sialyl-Tn and Ki67 (a proliferation marker) in KA and cSCC.
• To determine the relationship between Sialyl-Tn expression, tumor type, cell proliferation, and clinical factors like immunosuppression.

Main Methods:

• Immunohistochemistry was used to examine Sialyl-Tn and Ki67 expression in 27 KAs and 29 cSCCs.
• Parallel sections and double immunofluorescence were employed to analyze antigen co-expression.

Main Results:

• Sialyl-Tn was significantly more expressed in basaloid tumor cells of KAs (59%) compared to cSCCs (10%) (p<0.001).
• Differentiated tumor cells showed higher Sialyl-Tn positivity in KAs (89%) than in cSCCs (31%) (p<0.001).
• Sialyl-Tn expression was inversely correlated with Ki67, suggesting it is not linked to proliferation but rather to post-mitotic cells.
• No difference in Sialyl-Tn expression was observed between KAs from transplant recipients and non-immunosuppressed patients.

Conclusions:

• Sialyl-Tn expression patterns differ significantly between keratoacanthomas and squamous cell carcinomas.
• Sialyl-Tn is associated with differentiated, post-mitotic cells and not directly with proliferation or a malignant phenotype.
• Sialyl-Tn may play a role in tumor regression, a characteristic feature of keratoacanthomas.