Clear cell acanthoma with changes of eccrine syringofibroadenoma: reactive change or clue to etiology?

We observed two patients with solitary lesions showing features of clear cell acanthoma with underlying eccrine syringofibroadenoma-like changes. The pathogenesis of these entities has been debated since their original descriptions, with most recent literature suggesting that both may represent reactive phenomena rather than true neoplasms. Our observation prompted us to perform a retrospective review of clear cell acanthoma cases to determine the frequency of such associated eccrine syringofibroadenoma changes. Of 47 examined cases of clear cell acanthoma, 9 (19%) showed associated changes of eccrine syringofibroadenoma. Immunohistochemical evaluation performed on a subset of cases identified similar but slightly divergent differentiation patterns within the lesions. While epithelial membrane antigen and PAS expression were similar in both components (although slightly different in intensity), the regions resembling eccrine syringofibroadenoma displayed additional immunoreactivities, supporting the presence of two distinct components. We have found that the concurrence of clear cell acanthoma with syringofibroadenomatous changes is more frequent than generally appreciated and suggest that these entities may share derivation from the eccrine apparatus.