ECTOPIC NUCLEOLAR ORGANIZER REGIONS - A COMMON ANOMALY REVEALED BY AG-NOR STAINING OF METAPHASES FROM 9 CANCERS

In view of the sparsity of reports on nucleolar organizer regions (NOR s) in human tumor metaphase chromosomes, we have applied the silver (A g-NOR) technique to a previously studied testicular germ-cell tumor th at had an abnormal translocation, which involved a 13p, and to nine ne w sequentially studied tumors. Six of the new tumors, and the germ cel l tumor, showed ectopic NORs (e.g., at the end of the long arm of acro centrics or metacentrics, or interstitially in metacentrics):five carc inomas and a leiomyosarcoma, all of which also revealed numerous struc tural chromosome changes after G-banding. The three tumors that did no t show ectopic NORs were lymphomas with relatively simple karyotypic c hanges. It seems that the presence of ectopic NORs in the majority of the tumors is a reflection of the multiplicity of structural changes i n these tumors and does not signify that there is any particular prope nsity for acrocentrics to take part in these changes. Ii was interesti ng that several of the chromosomes showed large, apparently duplicated , NORs, notably a metacentric in a squamous cell carcinoma of the skin in which the Ag-NOR-positive region was seen as an unstained gap in u nbanded and G-banded chromosomes.