A benign neoplasm looks a lot like the tissue with normal cells from which it originated, and has a slow growth rate. Benign neoplasms do not invade surrounding tissues and they do not metastasize. Thus, characteristics include:
Resemblance to tissue of origin (well differentiated)
Lack of invasion
Absence of metastases
Benign neoplasms usually arise in a solitary manner (e.g., lipoma of colon, meningioma of brain), but may be multiple (e.g., leiomyomata of uterus, intradermal nevi of skin). Though benign, they may cause problems through mass effect, particularly in tight quarters (pituitary adenoma in the sella turcica).
A hamartoma is a peculiar benign neoplasm which is a localized but haphazard growth of tissues normally found at a given site (pulmonary hamartoma has jumbled cartilage, bronchial epithelium, and connective tissue)
A choristoma is a benign neoplasm consisting of tissue that is not normal to
the site of origin (e.g., salivary gland choristoma of the middle ear).