Elastosis Amyloidosis as a Histologic Pattern in Cutaneous Amyloidosis.

Elastosis amyloidosis is an exceptionally rare form of cutaneous amyloidosis characterized by amyloid deposition around dermal elastic fibers. To date, only 11 cases have been documented in the literature, some of them with associated systemic involvement. We report a case of a 60-year-old man presenting with an asymptomatic umbilical nodule. Histopathological analysis revealed amyloid deposits in the upper reticular dermis with characteristic distribution around the elastic fibers, confirmed by positive staining with PAS and Congo red. Immunohistochemical staining was positive for cytokeratins but negative for light chains and other systemic amyloid markers, leading to a diagnosis of elastosis amyloidosis with deposit of amyloid-AK, a finding previously unreported. We consider this an incidental discovery that may provide new insights into the etiopathogenesis of amyloidosis in both localized and systemic processes.