Degenerative nuclear atypia in pleomorphic adenoma of salivary glands: Histological and immunohistochemical observations.

The occurrence and topographical distribution of nuclear changes regarded as degenerative were examined in 84 salivary pleomorphic adenomas (PAs). Haematoxylin and eosin-stained sections from them were light-microscopically studied for unusual variations in size, shape and chromatin pattern of tumour-cell nuclei. Selected cases were further examined by immunohistochemical techniques valuable in characterising cell phenotypes in PA, and cell cycle antigens. A single case (female, 26 years, palate; 1.2 %) showed prominent cells with eosinophilic cytoplasm and variably enlarged or giant, irregularly shaped and occasionally multi-vacuolated nuclei with condensed or stippled chromatin and no mitoses. These cells were variably dyscohesive and did not line lumina; were cytokeratins 5/6, 7 and 14 (+, cytoplasmic), smooth muscle actin (+, cytoplasmic), p63 (+, nuclear), S-100 protein (+, nuclear and cytoplasmic), and WT1 and podoplanin (+/-, cytoplasmic); and did not stain for DOG1, CD63, p16 or Ki67. The nuclear vacuoles were cytokeratin and WT1 (+) - hence, interpreted as cytoplasmic inclusions. Degenerative nuclear atypia in PA seems rare, associated with non-cycling, non-luminal cells of myomatous ('myoepithelial') or schwannomatous phenotype and not related to malignant transformation. The particular phenotype of the affected cells suggests similarities to the degenerative nuclear atypia in pleomorphic leiomyoma and ancient schwannoma.