may help promote the survival and growth of the ssmc-bearing neoplastic cells in atms. as a result of these complicating factors, the specific genetic material in the sscms and giant marker chromosomes responsible for the development of alts have not been established. osteosarcomas low grade osteosarcomas (lgo), including low grade central and parosteal osteosarcomas, are far less malignant than most other types of osteosarcoma bone tumors. the tumor cells in lgo contain either supernumerary ring ssmcs or giant rod-shaped marker chromosomes (also termed giant rod chromosomes or rgms). rgms are supernumerary (i.e. extra) chromosomes that are larger than chromosome 20 and therefore here regarded too large to be classified as ssmcs. the ssmcs and rgms in lgo contain a part of the q arm of chromosome 12 that includes its band 13 through band 15 (notated as 12q13-15). several genes amplified in the neoplastic cells of various other types of cancer are in and thereby may be amplified in the lgo-associated ssmc and giant rod chromosomes. these genes include mdm2, cdk4, frs2, hmga2, yeats4 (yeats4 is yeats domain containing 4), and cpm. the mdm2, cdk4, and frs2 genes are amplified in 67% to 100% of all lgo cases and are suspected of contributing to the development and/or progression of lgos. however, both the ssmcs and rgms in lgo commonly contain parts of various other chromosomes, may be multiple, and often undergo changes in there genetic material during cell divisions. consequently, the specific genetic material responsible for the formation and development of lgo has been difficult to define. gonadal tumors in the tuner syndrome most individuals with turner syndrome have one x and no y chromosome. however, about 5.5% of turner syndrome individuals have an ssmc containing part of a y chromosome. this partial y chromosome-bearing ssmc may include the sry gene located on the p arm of the y chromosome at band 11.2 (notated as yp11.2). this gene encodes the testis-determining factor protein (also known as sex-determining region y protein). turner syndrome individuals with this sry gene-containing ssmc have an increased incidence of developing gonadal tissue neoplasms such as gonadoblastomas and in situ seminomas (also termed dysgerminoma to indicate that this tumor has the pathology of the testicular tumor, seminoma, but develops in ovaries). otherwise, these individual have typical features of the turner syndrome except for a minority who also have hirsutism and/or clitoral enlargement. surgical removal of the gonads has been recommended to remove the threat of developing these ssmc-associated neoplasms. tuner syndrome individuals with ssmcs that lacks the sry gene are not at an increased risk of developing these cancers. isochromosome i (5p)(p10)-associated cancers a ssmc containing isochromosome i (5p)(p10) (see above section on the isochcromosome 18p syndrome) has been documented to be present in the malignant cells of certain types of cancer. its presence in these cells is not due to inheritance but rather to cancer-related mutations in the bearer's genome. ssmc i(5)(p10) is the single most common recurrent structural chromosomal abnormality in transitional cell carcinomas of the urinary bladder, being present in the malignant cells of most cases of this disease. transitional cell bladder carcinomas associated with this ssms are more aggressive and invasive than those not associated with it. ssmc i(5)(p10), often in two or more copies, is also found in the malignant cervical cancer cells of individuals as well as in the oldest and most commonly studied immortalised cell line, hela cells. these cells were isolated from the cervix tumor of henrietta lacks, a 31-year-old african-american who died of her cancer in 1951. ssmc i (5)(p10) is also detected in rare cases of ovarian cancer and very rare cases of breast cancers. the mechanism(s) by which these ssmcs promote the development and/or progression of these cancer types is unclear.