| Namespace | MPheno.ontology | Obsolete | false |
| description | any structural abnormality of the circular ingrowth of the epidermis around the origin of the mammary cord (mammary sprout); in female mouse embryos, the nipple sheath is the first histological evidence of nipple formation seen at E16.5; at E18, the epidermis at the bottom of this epidermal ingrowth is lifted, making a rounded elevated portion, which is the anlage of the nipple |