Plaque-type syringoma: Two cases misdiagnosed as microcystic adnexal carcinoma

Background: Plaque-type syringoma is a rare variant of syringoma. This benign neoplasm may be easily misdiagnosed as microcystic adnexal carcinoma (MAC), potentially resulting in unnecessary surgery with disfiguring consequences. Methods: We report two cases of plaque-type syringoma that were initially diagnosed as MAC. Microscopically, these lesions were composed of nests of cuboidal cells arrayed within sclerotic collagen in the upper dermis. The deep reticular dermis was spared. No perineural involvement was observed. Results and Conclusions: Our cases are discussed in the context of histopathologic diagnosis. Detailed histopathologic findings of syringoma, as well as other considerations in the differential diagnosis, are reviewed. We also include a review of all cases of plaque-type syringoma published to date.