A new cytogenetic subgroup in lipomas: loss of chromosome 16 material in spindle cell and pleomorphic lipomas.

Six spindle cell lipomas and two pleomorphic lipomas were analyzed cytogenetically. One spindle cell lipoma had a supernumerary ring chromosome as the sole anomaly. The other five spindle cell lipomas and both pleomorphic lipomas had hypodiploid stemlines with monosomy 16 or unbalanced aberrations leading to loss of 16q13-qter, a feature distinguishing these lipoma subtypes from other benign and borderline adipose tissue tumor histotypes. unbalanced aberrations of chromosomes 13 and 10 were found in five and three cases respectively; 13q12 was lost in all of these cases, whereas there was no common deleted segment in chromosome 10. No aberrations involving 12q13-15, which are frequent in typical lipomas, were found. Both pleomorphic lipomas, but none of the spindle cell lipomas, had hypotetraploid sidelines, multiple nonclonal aberrations, and telomeric associations. The present findings reveal a new cytogenetic/histopathological association in adipose tissue tumors.