Carcinoma ex pleomorphic adenoma: a comprehensive review of clinical, pathological and molecular data

Abstract

Carcinoma ex pleomorphic adenoma (Ca ex PA) is a carcinoma arising from a primary or recurrent benign pleomorphic adenoma. It often poses a diagnostic challenge to clinicians and pathologists. This study intends to review the literature and highlight the current clinical and molecular perspectives about this entity. The most common clinical presentation of CA ex PA is of a firm mass in the parotid gland. The proportion of adenoma and carcinoma components determines the macroscopic features of this neoplasm. The entity is difficult to diagnose pre-operatively. Pathologic assessment is the gold standard for making the diagnosis. Treatment for Ca ex PA often involves an ablative surgical procedure which may be followed by radiotherapy. Overall, patients with Ca ex PA have a poor prognosis. Accurate diagnosis and aggressive surgical management of patients presenting with Ca ex PA can increase their survival rates. Molecular studies have revealed that the development of Ca ex PA follows a multi-step model of carcinogenesis, with the progressive loss of heterozygosity at chromosomal arms 8q, then 12q and finally 17p. There are specific candidate genes in these regions that are associated with particular stages in the progression of Ca ex PA. In addition, many genes which regulate tumour suppression, cell cycle control, growth factors and cell-cell adhesion play a role in the development and progression of Ca ex PA. It is hopeful that these molecular data can give clues for the diagnosis and management of the disease.

Fig. 1

a Ca ex PA demonstrating the co-existence of PA (left) and carcinoma (right) components (H&E, original magnification ×10). b Higher magnification of the PA area in a composed of glands with myoepithelial cells radiating out in a myxoid stroma (H&E, original magnification ×40). c Higher magnification of the carcinoma area in a composed of a poorly-differentiated adenocarcinoma with scanty glandular formation, marked nuclear pleomorphism and atypical mitosis (H&E, original magnification ×40)

Fig. 2

Ca ex PA with invasion outside the capsule. The carcinoma forms tiny glands and nests infiltrating through the capsule into the adjacent adipose tissue (H&E, original magnification ×2)