Keratoacanthomas (KAs) are tumors of epidermal origin characterized by a rapid growth rate. Since 1950, there has been controversy as to whether KAs are pseudobenign tumors with a distinct clinical behavior or pseudomalignant tumors and the potential of progressing to squamous cell carcinomas (SCCs), as well as to how they should be treated.1-13 Squamous cell carcinoma is the second most frequent form of skin cancer, representing 20% after basal cell carcinomas.1,3,8,9,12,13
The actual incidence of KA is unknown because many lesions are treated as SCCs and others are not treated by physicians at all because of their tendency to regress spontaneously. In various studies, the reported incidence ranges from 22.1 to 150 cases in populations of 100,000 inhabitants.4,8,11
Differentiating between KA and SCC is crucial because the therapeutic approach for each pathological entity is substantially different. In the case of KA, treatment consists of extirpating the lesion, whereas SCC treatment requires the excision of the lesion, with margins up to 1 cm wide to warrant a higher cure rate.1,4,8,14
Histopathologic examination remains the golden standard for diagnosis.1,2,8,10,14 Diagnosing KA is a difficult matter because its histopathologic criteria have little sensibility and specificity.1,2,8,10,15 The ambiguity in the diagnostic methods that are currently used to differentiate these 2 entities results in increased health care costs, the need for reinterventions, and increases in patient morbidity attributable to the reconstructive treatments.
The syndecan family is made up of heparan sulphate proteoglycans that are present on the cell surface. These molecules are important to the cellâ€™s cohesion and adhesion functions, allowing it to maintain its normal architecture as well as to migrate, differentiate itself, and grow.16-18 Syndecan-1 (CD138) is important in the progression of neoplastic cells to their metastatic phenotype.19-22 In SCCs of the head, neck, and larynx, the lesser expression of syndecan-1 is related to a more aggressive tumor behavior. Various studies have reported its use as a carcinoma prognostic marker.16-18,20,22-26
Ki-67 is a protein that is probably needed for cellular proliferation. It is associated with ribosomal RNA transcription, and its inactivation therefore leads to inhibition of RNA synthesis. Thanks to this, Ki-67â€™s expression is helpful in determining the growth rate of a cellular population.27-29
Differences in the expression patterns of syndecan-1 and Ki-67, in both KA and SCC, have been described. A correlation between the expression of both immunomarkers has not however been established.20,22,30