Cytogenetical observations in two cases of polymorphous low-grade adenocarcinoma of the salivary glands.

The cytogenetical findings in two cases of cultured salivary polymorphous low-grade adenocarcinoma (PLGA) are reported. The first PLGA was a carcinoma ex pleomorphic adenoma of the parotid gland. This had a pseudodiploid stemline characterized by extensive and complicated structural rearrangements. The chromosomal findings showed many similarities to those in the only previously studied case of PLGA (also a carcinoma ex pleomorphic adenoma of the parotid). The results in both could fit with abnormalities superimposed on those typical of mixed tumors. The second PLGA reported derived from a minor salivary gland. It showed a completely different picture, distinguished by a hypodiploid, almost exclusively numerical, variation and the occurrence of a stemline characterized by only monosomy 22. Etiological differences were proposed as one possible explanation for the cytogenetical differences between the two types of PLGA.