Two cases of hyperkeratosis of nipple and areola

We report two cases of hyperkeratosis of nipple and areola. Case 1 was a 55-year-old man. He visited our hospital after scattered black papules were observed on both areolae at a medical examination for healthcare survey. Case 2 was a 32-year-old man. He visited a local clinic, because of dark-red papules present on the left nipple and areola for several years. Both subjects were diagnosed with hyperkeratosis of nipple and areola based on clinical and pathological findings. Case 1 was associated with malignant melanoma, and Case 2 was associated with rachitis. Because this skin disorder was sometimes reported to be associated with malignant tumors or cryptorrhea in the past, it should be considered with more attention at the level of clinical practice.