Pleomorphic adenomas of the salivary glands: retrospective multicentric study of 130 cases with emphasis on histopathological features

Abstract

Pleomorphic adenoma (PA) is the most frequent benign epithelial lesion of salivary gland origin, showing great histopathological diversity. The aim of this study was to perform a retrospective analysis, with emphasis on histopathologic features of PA of salivary glands. Clinical and histopathologic characteristics of 130 cases of minor and major salivary glands PAs from three Brazilian reference centers were studied. Higher frequency of PAs was observed in female (55.4 %) subjects, with mean age of 49.7 years. The most common affected site was palate (64.5 %) for the PAs of minor salivary glands and parotid for cases affecting major glands (86.2 %). Microscopically, most cases were classified as classic PAs (50 %). Incomplete capsule was observed in 36.2 % of the cases, while 47.2 % showed capsular infiltration. Rounded (66.9 %), angular (49.2 %), oval (46.2 %) and plasmacytoid (39.2 %) cells were widely observed, as well as fibrous (73.8 %) and myxoid (69.2 %) stroma, squamous metaplasia (25.4 %) and cystic degeneration (43.1 %). Crystalloids (3.1 %), increased mitotic activity (5.4 %) and vascular invasion (2.3 %) were rarely observed. PAs arising in minor salivary glands were associated with incomplete capsules, spindle, oval, angular, plasmacytoid and pleomorphic cells, fibrous and hyaline stroma, cystic degeneration, squamous metaplasia and pleomorphism (p < 0.05). No association between capsular features and histological subtype was noted (p ≥ 0.05). These results confirm the findings of previous studies regarding major clinicopathological features of pleomorphic adenomas; and highlighted some important morphologic characteristics like the capsule, vascular invasion, pleomorphism and increased mitotic activity, which can reflect the biological behavior of these tumors.

Pleomorphic adenoma of the head and neck in children: presentation and management

“…On the cellular level, these tumors display great diversity in growth and morphology. Typically, they are made up of a mixture of duct‐like structures that recapitulate myoepithelial cells, exhibiting morphology including spindled, rounded, angular, plasmacytoid, polygonal, and mucous appearance . Although PA is benign, these tumors can be challenging to adequately treat due to proximity to the facial nerve, tendency to recur, and risk of malignant transformation.…”

“…Although PA is benign, these tumors can be challenging to adequately treat due to proximity to the facial nerve, tendency to recur, and risk of malignant transformation. The risk of recurrence ranges from 2.8% to 46.6%, depending on the surgical technique and tumor location, and can occur up to 10 to 15 years after surgery . Malignant transformation has been reported to occur at a rate of 3% to 13.3% …”

“…Recurrence rates depend largely on surgical technique, ranging from 1% to 4% for superficial parotidectomy to 40% to 50% for enucleation . Malignant transformation can occur in 3% to 13.3% of cases, and the incidence increases with time . Given the long life expectancy of children treated for PA, these risks are amplified in this population …”

Subtyping salivary gland neoplasm of uncertain malignant potential based on cell type demonstrates differential risk of malignancy

“…The morphologic heterogeneity may occur in a single tumor type because of tumor differentiation, metaplasia, tissue change, or reaction. For example, it is not uncommon to observe squamous metaplasia or cystic change in a pleomorphic adenoma, which causes diagnostic confusions . Moreover, even a single cell type can present with diverse cytomorphology.…”

“…For example, it is not uncommon to observe squamous metaplasia or cystic change in a pleomorphic Cancer Cytopathology November 2018 adenoma, which causes diagnostic confusions. [2][3][4][5] Moreover, even a single cell type can present with diverse cytomorphology. For instance, myoepithelial cells can be spindle-shaped, epithelioid, plasmacytoid, or even clear.…”