Monarch Disease Ontology identifier MONDO_0021165 (Paget disease) is a malignant neoplasm composed of large cells with large nuclei, prominent nucleoli, and abundant pale cytoplasm (Paget cells). Paget cell neoplasms include Paget disease of the nipple and extramammary Paget disease which may affect the vulva, penis, anus, skin and scrotum. Also known as: Paget's cell neoplasm, Paget's disease.