Reactive eccrine syringofibroadenomatosis secondary to primary cutaneous amyloidosis: a novel association

We report the unprecedented case of reactive eccrine syringofibroadenoma (ESFA) secondary to primary cutaneous amyloidosis. A 62-year-old woman of Asian ethnicity presented with a pruritic rash on the back of long-standing duration. Physical examination revealed diffuse hyperpigmentation localized to the interscapular region; there were a multitude of hyperpigmented macules merged in a rippled pattern intermixed with scattered papules and cobblestone-like areas. A punch biopsy from a papule was taken. Histopathological examination revealed a network of epithelial strands and cords hanging from the epidermis and harboring foci of ductal differentiation. Eosinophilic collections of amorphous material were found between the epithelial strands, obscuring the superficial dermis. The microscopic picture was consistent with primary cutaneous amyloidosis associated with reactive ESFA. Results of histochemical and immunohistochemical staining confirmed the diagnosis. We speculate that pathogenetic mechanisms intrinsic to primary cutaneous amyloidosis, in addition to unknown genetic factors, resulted in clinical changes of lichen amyloidosus associated with an abnormal hyperplastic epithelial response with histopathological features of ESFA rather than the common epidermal change of acanthosis and hyperkeratosis.