Abstract

Primary cutaneous amyloidosis (PCA) is characterized by amyloid deposition in the superficial dermis without involvement of other tissues and organs. Rare cases of PCA, also referred to as lichen amyloidosis, localized to the auricular concha and external ear have been described. We present a 68-year-old woman with interstitial lung disease and several asymptomatic, 2-3mm brown-tan, dull stuck -on papules in the right and left auricular cymba conchae. Differential diagnoses included seborrheic keratoses and atypical melanocytic nevi. A shave biopsy was performed, which revealed variably sized globules of amorphous, eosinophilic material in the papillary dermis with admixed dendritic melanophages. The overlying epidermis demonstrated acanthosis, vacuolar basal degeneration, orthohyperkeratosis, and follicular plugging. In many foci the eosinophilic material was embraced by gently elongated rete. Congo red staining exhibits focal brick red positive staining in the papillary dermal deposits, consistent with amyloid. Additionally, there was more diffuse positive staining for CK5/6 indicating the presence of basic (type II) cytokeratin, thus supporting primary cutaneous or keratin derived amyloid. She was diagnosed with PCA of the auricular concha. While CK5/6 positivity has been reported in lichen and macular PCA, to our knowledge, there is no description of CK5/6-positive PCA of the auricular concha. This may support the hypothesis that PCA of the auricular concha exists on a continuum with other PCA subtypes, rather than representing an entirely distinct entity. Additionally, while previously reported cases describe PCA as skin-colored papules, our case indicates that PCA of the auricular concha may present as hyperpigmented papules that clinically resemble small seborrheic keratoses or melanocytic proliferations.

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