Cell kinetics of pleomorphic adenomas of the parotid gland

Why Do Parotid Pleomorphic Adenomas Recur? A Systematic Review of Pathological and Surgical Variables

Background

The recurrence of pleomorphic adenoma (PA) has been extensively debated, mostly in relation to the extent of parotidectomy.

Methods

A systematic review was undertaken to clarify the surgical and pathological variables related to PA recurrence. Inclusion criteria were as follows: English literature, and prospective or retrospective studies. Exclusion criteria were as follows: single case reports, reviews, and lack of PA recurrence data.

Results

Pathology-related variables associated with recurrence include the histological subtype, the thickness and incompleteness of the tumor capsule, pseudopodia, and satellite nodules. Surgery-related variables associated with recurrence are the presence of intact margins and tumor puncture or spillage. Other factors are the size of the tumor and the age of patient. Myxoid subtypes of PA tend to have incomplete and thinner capsules and to recur more frequently. Surgical variables related to recurrence include positive margins and tumor spillage.

Conclusion

Myxoid and/or large PA, especially in young patients, should be approached more cautiously to avoid recurrences.

Metachronous pleomorphic adenomas occurring in the parotid and a minor salivary gland with genetic changes detected by comparative genomic hybridization

A 32-year-old female underwent an extracapsular dissection for a pleomorphic adenoma (PA) of the parotid gland. Six months later, she presented with an increasing lump on the upper lip that, following excision, was confirmed to be a second PA. Formalin-fixed paraffin embedded tissues were analyzed for chromosomal aberrations. Comparative genomic hybridization analysis showed multiple chromosomal aberrations in the parotid PA. In comparison, no chromosomal aberrations were found in the lip PA. To our knowledge, metachronous benign pleomorphic adenomas occurring in both a major and minor salivary gland is unreported, and furthermore, there are no comparative genomic hybridization reports of this rare occurrence. We discuss the clinicopathological implications.

Immunolocalization of beta-catenin in pleomorphic adenomas and carcinomas ex-pleomorphic adenomas of salivary glands

Beta-catenin plays a central role in cadherin/catenin cell-cell adhesion complex and is involved in cell signaling pathway. Change in beta-catenin distribution has been associated with several human cancers including salivary gland tumors. We studied the immunolocalization of beta-catenin in a series of pleomorphic adenomas (PA) and carcinomas ex-pleomorphic adenomas (Ca ex-PA). Ten samples of PA and ten of Ca ex-PA were evaluated by immunohistochemistry using streptavidin-biotin-peroxidase technique and a monoclonal antibody against beta-catenin (E-5). Cell membrane/cytoplasmic staining of beta-catenin was observed in normal gland parenchyma, PA, and in well-differentiated Ca ex-PA. Cytoplasmic/nuclear beta-catenin staining was observed in poorly differentiated carcinomas and, interestingly, in one case of PA. Our data showed decreased cell membrane beta-catenin expression in higher-grade tumors suggesting that beta-catenin may play an important role in histologic differentiation and transition to malignant phenotype of Ca ex-PA.

[DNA ploidy and proliferative activity in salivary gland tumours]

DNA ploidy and S-Phase fraction (SPF) of 279 salivary gland tumours were analysed using high-resolution DNA flow cytometry. All 229 benign neoplasms were diploid while 12 of 50 malignant tumours showed cell populations with aneuploid DNA content. The SPF values of diploid malignancies were significantly higher if compared with pleomorphic adenomas but did not differ from that of the zystadenolymphoma (Warthin tumour) group. While aneuploidy represents a distinct indicator of malignancy SPF values are of minor relevance for dignity assessment in salivary gland tumours.