Differentiation of keratoacanthoma from squamous cell carcinoma by argyrophilic nucleolar organizer region (AgNOR) staining

The objective was to evaluate the differentiation of keratoacanthoma from
squamous cell carcinoma by using argyrophilic nucleolar organizer region staining.
Methodology: Thirty one cases of keratoacanthoma and 31 cases of squamous cell carcinoma
(S.C.C) were selected. The AgNOR staining carried out. Counting of AgNOR was done in 100
cells of each tumor. Two criterias including M.AgNOR (mean number of AgNORs) and P.AgNOR
(percentage of nuclei with five or more than five AgNORs per nucleous) were used. Statistical
analysis was done by Mann- Whitney test.
Results: Significant increase in M.AgNOR and P.AgNOR was found in S.C.C compared with
keratoacanthoma ( M.AgNOR =16.52 ± 10.1 and P.AgNOR = 84.12 ± 23.4 in S.C.C compared with
M.AgNOR = 6.58 ± 4.4 and P.AgNOR = 52.29 ± 26.7 in keratoacanthoma, P=0.000). Exceptionally
overlapping was seen.
Conclusion: This study indicated that the AgNOR counting is a valuable diagnostic criterion for
differentiation of keratoacanthoma and S.C.C especially in cases with borderline histologic
features.