Unilateral Primary Localised Cutaneous Nodular Amyloidosis of the Nipple: Nipple amyloidosis

Background: Amyloidosis is characterised by extracellular accumulation of an amorphous fibrillary protein and can affect any organ. It is classified into systemic and localised disease according to its sites of presentation and as primary or secondary according to aetiology. Breast amyloid was first described in 1973 and is extremely rare.Case Presentation: A 61-year-old woman presented in 2020 with a 1-year history of an enlarging tender left nipple with some associated bleeding. Clinical differential diagnoses included a nipple adenoma and an intraductal carcinoma; therefore, a punch biopsy was taken. A full set of screening blood tests were undertaken which were normal, showing no evidence of a plasma cell dyscrasia.The biopsy showed diffuse replacement of the dermis by acellular eosinophilic material showing fracturing. Congo Red stain was positive showing apple-green birefringence under polarised light. A diagnosis of primary localised cutaneous nodular amyloidosis of the nipple was made.Conclusion: We present a rare documented case of isolated primary localised cutaneous nodular amyloidosis of the nipple. This can be considered as a differential diagnosis for patients with a new nipple lesion alongside nipple adenoma and intraductal carcinoma.