Keratoacanthoma : Differential Diagnosis
Keratoacanthoma has to be distinguished from conventional squamous cell carcinoma. The usual histologic criteria are not helpful in this regard due to overlapping features. There are no specific immunohistochemical markers that can be used in the differential diagnosis. There are molecular differences between keratoacanthoma and squamous cell carcinoma; however, there are no practical ways of exploiting these differences in routine diagnosis.
Adequate clinical history and, if possible, the availability of the entire lesion for microscopic examination are crucial for making an accurate diagnosis. An ideal specimen is an excisional or a deep incisional biopsy. The diagnosis should not be rendered on a limited and fragmented specimen. Ultimately, if the doubts persist about the final diagnosis, it is best to consider the lesion as squamous cell carcinoma and perform complete surgical excision.
The image shows a mixed inflammatory infiltrate with eosinophils on the deeper aspect of a keratoacanthoma.