A mature teratoma often contains several different types of tissue such as skin, muscle, and bone. Skin may surround a cyst and grow abundant hair (see dermoid cyst). Mature teratomas generally are benign, with 0.17-2% of mature cystic teratomas becoming malignant. Immature teratoma
Immature teratoma is the malignant counterpart of the mature teratoma and contains immature tissues which typically show primitive or embryonal neuroectodermal histopathology. Immature teratoma has one of the lowest rates of somatic mutation of any tumor type and results from one of five mechanisms of meiotic failure. Gliomatosis peritoneii
Gliomatosis peritoneii, which presents as a deposition of mature glial cells in the peritoneum, is almost exclusively seen in conjunction with cases of ovarian teratoma. Through genetic studies of exome sequence, it was found that gliomatosis is genetically identical to the parent ovarian tumor and developed from cells that disseminate from the ovarian teratoma. Dermoid cyst
A dermoid cyst is a mature cystic teratoma containing hair (sometimes very abundant) and other structures characteristic of normal skin and other tissues derived from the ectoderm. The term is most often applied to teratoma on the skull sutures and in the ovaries of females. Fetus in fetu and fetiform teratoma
Fetus in fetu and fetiform teratoma are rare forms of mature teratomas that include one or more components resembling a malformed fetus. Both forms may contain or appear to contain complete organ systems, even major body parts such as a torso or limbs.
Halls is a plural of the word hall. Halls may also refer to:

People
Walter Halls (1871–1953), British trade unionist and politician
Ethel May Halls (1882–1967), American actress
Julian Halls (born 1967), British field hockey player
Evelyn Halls (born 1972), Australian fencer
Roxana Halls (born 1974), English artist
Monty Halls (born 1976), British marine biologist and TV presenter
John Halls (born 1982), English footballer, mostly played for Stoke, Brentford and Aldershot, and model
Andy Halls (born 1992), English footballer, has played for Stockport, Macclesfield and Chester
Halls (footballer) (born 1999), Brazilian footballer
Henrique Halls (born 2002), Brazilian footballer

Places
Halls, Georgia, an unincorporated community
Halls, Missouri, an unincorporated community
Halls, Tennessee, a town in West Tennessee
Not to be confused with Halls Crossroads, Tennessee, a suburb of Knoxville sometimes colloquially referred to as "Halls"

Business
Halls (cough drop), a brand of cough drop
Geo. Hall & Sons, a defunct Australian soft drink company
Halls (department store), Kansas City, Missouri, United States