Impact of the in vitro technique used on the cytogenetic patterns in pleomorphic adenomas.

The cytogenetic observations in 97 new cases of pleomorphic adenomas are reported. They were all studied by in vitro technique using enzymatic pretreatment of the explanted material. The results, together with 26 previously reported cases studied by the same method (series II), were compared with a group of 130 adenomas (series I) investigated in cultures of only mechanically dispersed material. The results showed that in series II there was a substantial reduction of normal stemlines, an increase of cases with t(3;8)(p21;q12) and, in particular, of those with other 8q12 involvement. There was a similar frequency of cases with 12q13-15 aberrations in both series whereas, in series II, there was a moderate increase of the cases with "unique" abnormal stemlines. In comparison the German material, comprising 220 cases also studied by the enzymatic method, revealed a much higher frequency of cases with a normal stemline and a much lower frequency of adenomas with 8q12-involvement and of cases with unique stemlines. The results emphasize the need and importance of a meticulous documentation of all details of the in vitro technique used, for instance: explantation methods, composition of media, growth periods in vitro, and methods of harvest.