Sekundäre hochmaligne Transformation eines niedrigmalignen epithelial-myoepithelialen Karzinoms

High-grade Transformation/Dedifferentiation in Salivary Gland Carcinomas: Occurrence Across Subtypes and Clinical Significance

High-grade transformation (HGT) or dedifferentiation has been described in a variety of salivary gland carcinomas, including acinic cell carcinoma, secretory carcinoma, adenoid cystic carcinoma, epithelial-myoepithelial carcinoma, polymorphous adenocarcinoma, low-grade mucoepidermoid carcinoma, and hyalinizing clear cell carcinoma. High-grade (HG) transformed tumors are composed of a conventional low-grade component characterized by specific microscopic and immunohistochemical features for the given entity, intermingled with or juxtaposed to areas of HG morphology. This is usually either poorly differentiated adenocarcinoma, carcinoma not otherwise specified, or undifferentiated carcinoma, in which the original line of differentiation is lost. The HG component is composed of solid nests of anaplastic cells with large vesicular pleomorphic nuclei, prominent nucleoli, and abundant cytoplasm. Frequent mitoses and extensive necrosis may be present. The Ki-67 labeling index is consistently higher in the HG component. The molecular genetic mechanisms responsible for HGT of salivary gland carcinomas are largely unknown, though p53 inactivation and human epidermal growth factor receptor 2 overexpression and/or gene amplification have been demonstrated in the HG component in a few examples, the frequency varies for each histologic type. Salivary gland carcinomas with HGT are more aggressive than conventional carcinomas, with a higher local recurrence rate and a poorer prognosis. They have a high propensity for cervical lymph node metastasis suggesting a need for a wider resection and neck dissection. HGT of salivary gland carcinoma can occur either at initial presentation or less commonly at the time of recurrence, sometimes following postoperative radiotherapy. The potential for HGT in almost any type of salivary gland carcinoma warrants a thorough sampling of all salivary gland malignancies to prevent oversight of a HG component.

Epithelial-myoepithelial carcinoma with high-grade transformation of parotid gland: A case report and literature review

RATIONALE

Epithelial-myoepithelial carcinoma (EMC) is regarded as a rare low-grade malignant tumor of the salivary gland, accounting for 0.4% to 1% of all salivary gland tumors. However, epithelial-myoepithelial carcinoma with high-grade transformation (EMC with HGT) is extremely rare, therefore it is easily to be inappropriately diagnosed and treated. Herein, we report an unusual case of EMC with HGT involving the parotid gland and discuss the clinical features and histological characteristic of EMC with HGT, in order to remind the doctors to take appropriate diagnosis and treatment.

PATIENT CONCERNS

A 77-year-old female sought for treatment in our hospital due to pain mass in the left parotid gland for 6 months with rapid growth recently.

DIAGNOSES

EMC with HGT was confirmed by final pathology, and then the result showed there were 2 distinctly different areas in the tumor, including the typical EMC component and intensive spindle cells component.

INTERVENTIONS

The extensive resection surgery was performed.

OUTCOMES

The patient was uneventful after surgery and no recurrence or metastasis has been observed after follow-up of 4 years.

LESSONS

A review of literature suggested that EMC with HGT patients trend to be more aged, more aggressive and poorer prognosis than typical EMC patients. In order to avoid misdiagnosis and inappropriate treatment, it is necessary to accurately recognize the differences between the EMC with HGT and typical EMC.

"Dedifferentiation" and high-grade transformation in salivary gland carcinomas

"Dedifferentiation" and/or high-grade transformation (HGT) has been described in a variety of salivary gland carcinomas, including acinic cell carcinoma, adenoid cystic carcinoma, epithelial-myoepithelial carcinoma, polymorphous low-grade adenocarcinoma, myoepithelial carcinoma, low-grade mucoepidermoid carcinoma and hyalinizing clear cell carcinoma, although the phenomenon is a rare event. Recent authors tend to preferably use the term HGT instead of "dedifferentiation" in these cases. HGT-tumors are composed of conventional carcinomas juxtaposed with areas of HG morphology, usually either poorly differentiated adenocarcinoma or "undifferentiated" carcinoma, in which the original line of differentiation is no longer evident. The HG component is generally composed of solid nests, sometimes occurring in cribriform pattern of anaplastic cells with large vesicular pleomorphic nuclei, prominent nucleoli and abundant cytoplasm. Frequent mitoses and extensive necrosis is evident. The Ki-67 labeling index is consistently higher in the HG component. p53 abnormalities have been demonstrated in the transformed component in a few examples, but the frequency varies by the histologic type. HER-2/neu overexpression and/or gene amplification is considerably exceptional. The molecular-genetic mechanisms responsible for the pathway of HGT in salivary gland carcinomas largely still remain to be elucidated. Salivary gland carcinomas with HGT have been shown to be more aggressive than conventional carcinomas with a poorer prognosis, accompanied by higher local recurrence rate and propensity for cervical lymph node metastasis, suggesting the need for wider resection and neck dissection.

Dedifferentiated epithelial-myoepithelial carcinoma: analysis of a rare entity based on a case report and literature review

Dedifferentiated epithelial-myoepithelial carcinoma (DEMC) is very rare salivary gland neoplasm with only anecdotal reports. We present an analysis of DEMC, based on a case and review of literature. Our patient, an 85-year-old woman, presented with a submandibular mass of 5 years duration that was increasing in size over a 5-week period. Histologically, there were areas of typical epithelial-myoepithelial carcinoma, with dedifferentiation of both components, manifesting morphologically as salivary duct carcinoma and areas of myoepithelial carcinoma. A review of literature revealed 21 previously reported cases of DEMC. DEMC occurs at an average age of 72 years, most often in the parotid gland (72%) followed by submandibular gland (17%). Dedifferentiation more often involves the epithelial component (13/15 cases) than the myoepithelial component (5/15 cases). Although typical epithelial-myoepithelial carcinomas are fairly indolent (average disease-free survival of 11.34 years), dedifferentiation confers a poor prognosis (survival reported from 1 to 72 months).

Current concepts on dedifferentiation/high-grade transformation in salivary gland tumors

The concept of dedifferentiation had previously been used in salivary gland carcinomas. Recently, the term “high-grade transformation” was introduced for adenoid cystic carcinoma, acinic cell carcinoma, epithelial-myoepithelial carcinoma, and polymorphous low-grade adenocarcinoma and may better reflect this phenomenon, although transformation into moderately differentiated adenocarcinoma (i.e., not “high grade”) has also been described. Among the immunohistochemical markers, Ki-67 seems to be the only one that can help distinguish between the conventional and transformed components; however, the combination of morphological criteria is still sovereign. The overexpression of p53 was observed in the transformed component in all tumor types studied, despite few cases having been demonstrated to carry mutations or deletions in TP53 gene. Genetic studies in salivary gland tumors with dedifferentiation/high-grade transformation are rare and deserve further investigation. This paper aims at providing an overview on the recent concepts in histopathological classification of salivary gland tumors, complemented by immunohistochemical and genetic findings.

Epithelial-myoepithelial carcinoma with high grade transformation

Epithelial-myoepithelial carcinoma (EMC) is a rare salivary gland tumor of presumed intercalated duct origin with a low risk of metastasis and mortality. Factors shown to affect behavior include positive margins, vascular invasion, necrosis, and myoepithelial anaplasia. The latter category and dedifferentiated EMCs have been separated on the basis of presumed myoepithelial versus ductal origin, respectively. Three additional cases of typical EMC with transition to high-grade carcinoma are presented. Two of the tumors were stained with CAM5.2, 34betaE12, cytokeratin 14, p63, S100, calponin, smooth muscle actin, and muscle-specific actin. All tumors showed a gradual transition to a high-grade carcinoma from an EMC, each composed of clear cells even in the high-grade regions. One case also showed a discrete area with ductal lumina and another had plasmacytoid morphology. Squamous differentiation was seen in all cases as well. A consistent immunostaining pattern was not noted. Areas with focal lumina were diffusely positive for CAM5.2 only. Areas with clear cells showed patchy S100 positivity only, whereas cytokeratin 14 and 34betaE12-stained squamous pearls. The case with plasmacytoid morphology was diffusely positive for p63. No immunoexpression was noted with smooth muscle actin, muscle-specific actin, or calponin. It was not possible to convincingly separate the high-grade component in these cases into ductal dedifferentiated EMC versus myoepithelial. Recently, there has been a move to abandon the term "dedifferentiation" in favor of "high-grade transformation" in other salivary gland malignancies. We report these 3 such cases, review the literature and propose that these lesions be regarded as "EMC with high-grade transformation."