Hybrid Carcinomas of the Salivary Glands: Report of Nine Cases with a Clinicopathologic, Immunohistochemical, and p53 Gene Alteration Analysis

Abstract

Hybrid carcinomas of the salivary gland are a recently defined and rare tumor entity, consisting of two histologically distinct types of carcinoma within the same topographic area. In this study, we examined nine such cases, which mainly arose in the parotid gland (seven cases), with an additional one each from submandibular and lacrimal glands, and analyzed their clinicopathologic profiles, including immunohistochemical features and p53 gene alterations. The prevalence of hybrid carcinomas was 0.4% among the 1863 cases of parotid gland tumors in our series. The nine patients comprised five men and four women, ranging in age from 40 to 81 years (mean, 62 y). Tumor size ranged from 2 to 10 cm (mean, 4.2 cm). Of the seven patients who were followed up, two were alive with disease and five were alive with no evidence of disease, although the follow-up period was short. Three cases had cervical lymph nodal metastases. The combinations of carcinoma components in our hybrid carcinomas were as follows: epithelial-myoepithelial carcinoma and basal cell adenocarcinoma in two cases, epithelial-myoepithelial carcinoma and squamous cell carcinoma in one case, salivary duct carcinoma and adenoid cystic carcinoma in two cases, myoepithelial carcinoma and salivary duct carcinoma in one, acinic cell carcinoma and salivary duct carcinoma in one, and squamous cell carcinoma and salivary duct carcinoma in two. Although the proportion of each carcinoma component in a tumor mass varied from case to case, the minor component always represented >10% of the area. Differences in cellular composition were studied by immunohistochemistry and electron microscopy. The Ki-67-labeling index apparently differed between the two carcinoma elements in five cases. Diffusely positive p53 immunoreactivity was observed in four cases, restricted to the more aggressive component in each pair. Furthermore, p53 gene alteration analysis of these p53-positive cases revealed that all and three cases demonstrated loss of heterozygosity at p53 microsatellite loci and p53 gene point mutations, respectively, which were detected only in the p53-immunoreactive carcinoma component. Therefore, there is the possibility that such molecular-genetic events take an integral part for inducing the transformation from histologically lower to higher grade tumor during the hybrid carcinoma genesis of the salivary glands.

Hybrid salivary gland tumor of the upper lip or just an adenoid cystic carcinoma? Case report

“…The tumor entities in a hybrid tumor are not separated but have an identical origin within the same topographical area" (1). This concept of hybrid tumor should not be confused with certain entities of the salivary glands that may exhibit two or more different morphologies in a single lesion, such as collision tumors (which are lesions that originate in separate regions but coalesce in a particular area), tumors with biphasic differentiation (single entities containing two different cellular types, such as pleomorphic adenomas), synchronous and multiple tumors, carcinomas with metaplastic change and other examples (2)(3)(4). While the possibility of developing multiple tumors that coalesce and invade each other and the production of collision tumors that simulate a single entity does exist in major salivary glands, the probability of this phenomenon to occur in the minor salivary glands is remote, and therefore the diagnosis of a hybrid tumor and tumors with biphasic differentiation should be strongly considered when the tumor contains two different tumor entities which are not separated and are located in the same topographical area.…”

“…These are very rare lesions, as they represent less than 0.1% of all salivary gland neoplasms. To date, there are less than 30 cases reported in the literature, most of which have been detected in parotid and palatine glands (2,3). The purpose of this article is to present a case of hybrid carcinoma of upper lip salivary glands, composed by adenoid cystic carcinoma (ACC) and epithelial-myoepithelial carcinoma (EMC), as well as to discuss its probable histogenesis and to describe its salient clinico-patological features, diagnosis and therapeutic approach.…”

Oncocytic and Apocrine Epithelial Myoepithelial Carcinoma: Novel Variants of a Challenging Tumor

“…Apocrine EMCa also appears to have an indolent course [13]. Interestingly, rare hybrid tumors of EMCa and salivary duct carcinoma have been described, and it is plausible that apocrine EMCa is an 'intermediary' or 'bridge' form to such a hybrid carcinoma [20].…”

Three cases of rare salivary gland tumours: a molecular study of TP53, CDKN2A/ARF, RAS, BRAF, PTEN, MAPK2 and EGFR genes

“…Hybrid tumours account for <0.1% of all salivary gland tumours (9). Recently cases of hybrid tumours reported in literature have been reviewed by Nagao et al (10). The identification of molecular markers should help either in the diagnostic process and to better understand the genetic mechanisms of pathogenesis in these very rare hystotypes.…”