Chromosomal Aberrations and Their Relation to Malignancy in Meningomas: A Meningoma With Ring Chromosomes

A benign human tumour, a hypodiploid meningoma, with a ring chromosome in its stemline is described. This study, together with previous findings in 11 other benign meningomas, demonstrates that neither considerable aneuploidy nor structural aberrations are reliable cytogenetical indicators of malignant transformation. In early in vitro passages of the present meningoma the hypodiploid stemline with the ring chromosome was replaced by a normal, diploid stemline, whereas a 45‐chromosome sideline with loss of one G chromosome was seen in all fixations. Outgrowth of stroma cells could be responsible for the stemline shift. The persisting sideline may represent a remnant of a stemline developed at an earlier period of the in vivo growth of the meningoma.