|Year : 2020 | Volume
| Issue : 2 | Page : 266-269
Epithelial myoepithelial carcinoma of the parotid gland: A rare tumor with oncocytic changes
HC Inan1, G Issin2
1 Department of Otorhinolaryngology, Erzincan Binali Yildirim University, Mengücek Gazi Training and Research Hospital, Erzincan, Turkey
2 Pathology, Erzincan Binali Yildirim University, Mengücek Gazi Training and Research Hospital, Erzincan, Turkey
|Date of Submission||30-May-2019|
|Date of Acceptance||26-Jul-2019|
|Date of Web Publication||7-Feb-2020|
Dr. H C Inan
Department of Otorhinolaryngology, Erzincan Binali Yildirim University, Mengücek Gazi Training and Research Hospital, Erzincan
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Epithelial myoepithelial carcinoma (EMC), a very rarely seen, low-grade, malignant, salivary gland tumor is most commonly located in the parotid gland followed by the submandibular gland. It is more often observed in females and in the 6th decade of life. Although primary treatment of the tumor is surgical resection, adjuvant radiotherapy may be applied to the adjacent area or close follow-up can be done if the surgical margin is closed. Patients must be followed up closely for recurrence and metastasis. Physical and radiological examinations (USG and MRI) should be performed to see for any recurrence in the operated area during the first year for every 2–3 months. This study presents the clinical, radiological, and pathological characteristics of a 59-year-old female patient with low-grade, oncocytic variant of EMC located in the left parotid gland.
Keywords: Epithelial myoepithelial carcinoma, parotid gland, salivary gland neoplasm
|How to cite this article:|
Inan H C, Issin G. Epithelial myoepithelial carcinoma of the parotid gland: A rare tumor with oncocytic changes. Niger J Clin Pract 2020;23:266-9
| Introduction|| |
EMC is a very rarely seen biphasic tumor, which constitutes 0.5–1% of all salivary gland neoplasms. The parotid gland is most often involved and occasionally there may be involvement of minor salivary glands. The nasal cavity, hypopharynx, soft palate, and paranasal sinuses are some of the areas where the disease may emerge. It is more often observed in females and at an older age (6th–7th decades of life). EMC was first described by Donath et al. in 1972, and entered the World Health Organization classification in 1991.
Patients often present a slow-growing mass. Masses originating from mucosal surfaces such as the hard or soft palate may emerge as ulcerated lesions. Despite being a low-grade malignancy, it demonstrates locally invasive properties. Therefore, to prevent a recurrence, total excision of the tumor with a good surgical margin is of great importance. Another challenging point related to these tumors is the diagnosis with fine-needle aspiration biopsy which is difficult. In differential diagnosis, other biphasic tumors such as pleomorphic adenoma, adenoid cystic carcinoma, and sebaceous carcinoma should be considered.
| Case Report|| |
A 59-year-old female was presented with a swelling on the left side of the face, which had been growing slowly for 2 years. Physical examination showed a mobile mass of hard texture, approximately 1.5 cm in size in the left parotid gland bed. The general head and neck examination and facial nerve function were normal.
On ultrasonography (USG) of the parotid gland, a heterogenous hypoechoic lesion was seen of 22 × 12 mm dimensions in the left parotid parenchyma, not showing evident bleeding on color flow doppler ultrasound. On magnetic resonance imaging (MRI) examination of the parotid gland, the lesion was seen to be hypointense on T1-weighted slices, hyperintense on T2-weighted slices, and did not show significant contrast after injection of contrast material [Figure 1]a. On computed tomography (CT) examination, the lesion was seen to be lobulated, contoured, and homogenously hyperdense [Figure 1]b. Fine-needle aspiration biopsy (FNAB) applied under USG guidance was reported as nondiagnostic. Based on this result, left-side superficial parotidectomy was performed. The mass was seen to be located on the facial trunk but there was no adherence to the nerve function [Figure 1]c. The mass was removed with intact margins along with the parotid superficial lobe. Postoperatively, the facial nerve functions were normal.
|Figure 1: a) Axial T2-weighted magnetic resonance image revealed hyperintense mass inside the left parotid gland. b) Axial CT images revealed a lobulated and homogenously hyperdense mass. c) Intraoperative relation between the mass and the facial nerve|
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Macroscopic examination of the resected specimen revealed a nodular, well-circumscribed mass about 1.8 × 1.6 × 1.5 cm in size and appearing brown-yellow in cut surface with no conspicuous necrosis or hemorrhage. Microscopic examination showed a normal parotid gland structure and multinodular tumor. Tumor nodules were well-circumscribed and surrounded by a thin fibrous connective tissue capsule. The tumor showed pushing edges with finger-like herniation [Figure 2]a. The tumor mass was formed by ductiform structures and sheets of polygonal-spindle cell with abundant oncocytic cytoplasm and uniform round nuclei. In ductiform structure area; the tumor comprised of two cell types, an inner layer of cuboidal oncocytic duct-like cells and an outer layer of oncocytic polygonal cells. The ducts contain eosinophilic proteinaceous material. Polygonal-spindle cells, arranged in sheets and ductiform areas were enveloped on the outer surface by eosinophilic material [Figure 2]b. With this finding; oncocytoma, myoepithelioma, mucoepidermoid carcinoma, mammary analog secretory carcinoma, adenoid cystic carcinoma, and EMC were included in the differential diagnosis
|Figure 2: a) Pseudopod-like prolonged tumor tissue in a space with a thin fibrous capsule around it (H and E; ×100). b) Tumor areas where there is a clear separation of epithelial myoepithelial component showing oncocytic changes (H and E; ×200). c) P63 expression in the outer part of the tubules structures in the myoepithelial layer (×400). d) CK7 expression in the epithelial layer of the tubules structures in the immunohistochemical examination (×200)|
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Histochemical examination showed that eosinophilic proteinaceous material in the ductus lumen was negative with Congo red and Mucicarmine staining while hemosiderin deposition was not observed with Prussian blue. In the immunohistochemical examination, SMA, P63, and P40 were positive on outer layer in the ductal structures [Figure 2]c, while CK7 and CK 5/6 were positive on inner layer in the ductal structures [Figure 2]d. Patchy S100 and Vimentin expression were observed in polygonal and cuboidal cells. The Ki-67 proliferation index was approximately 1%. Epithelial and myoepithelial cell components were identified and confirmed by immunohistochemistry. These findings corroborate the diagnosis of epithelial myoepithelial carcinoma with oncocytic changes. The diagnosis of EMC is based upon the identification of both epithelial and myoepithelial cell types confirmed with immunohistochemistry. Although tumor continuation was not observed in the surgical margins, the closest area of the tumor was 0.1 mm from the surgical margin.
The patient did not undergo radiotherapy and is doing follow-up for 12 months without any recurrence.
| Discussion|| |
Epithelial myoepithelial carcinoma (EMC) is an extremely rarely seen biphasic salivary gland tumor. There are variants which have been defined according to the cytoplasmic and nuclear characteristics. Of these, the oncocytic variant was described by Savera and Salama in 2005. A definitive diagnosis requires histopathological and immunohistochemical examinations. Histologically it is characterized by biphasic ductal structures, consisting of cuboidal epithelial cells lining the inner layer and surrounded by myoepithelial cells. The epithelial cells appear on the inner side in a single row, cuboid in shape with granular cytoplasm, and possess a central round nucleus. The outer myoepithelial cells are polygonal in shape in single or multiple layers. The cytoplasm is clear and the nucleus are vesicular.
Unlike the classic form, the oncocytic variant EMC has pink oncocytic cytoplasm in both epithelial and myoepithelial components. Since epithelial and myoepithelial layers can not be determined, this may cause a diagnostic challenge. There are many cell types and staining patterns in the differential diagnosis of EMCs. As oncocytic variant EMCs are rarely seen and reported cases have limited follow-up, there is insufficient knowledge about the effect on prognosis, but they have been observed to have a similar course to classic EMCs. Differentiation to the high-grade tumor may be seen in approximately 2% of EMCs. Though this may be observed in both components forming the tumor, it may also be seen in either the epithelial or myoepithelial component. Differentiation to the high-grade tumor has been associated with poor prognosis. In the current case, as oncocytic changes were observed in the whole tumor, differentiation to the high-grade tumor and vascular or perineural invasion were not seen. This could be attributed to the tumor not having grown rapidly over many years and remaining asymptomatic.
The primary treatment for EMC is surgical resection. Tumor recurrence may be seen in 40% of patients and metastasis in 14%. Metastases occur primarily in the cervical lymph nodes, the lungs, and the liver. High-grade EMCs respond well to radiotherapy (RT) and chemotherapy. Adjuvant radiotherapy is recommended for advanced-stage tumors (>4 cm) and cases with a positive surgical margin. Long-term follow-up is recommended for these patients as distant metastases and recurrences may emerge after a long time. In a case study by Davidoss et al., despite the invasion of the facial nerve by the tumor is seen macroscopically, as the nerve functions were normal, the nerve was protected and adjuvant RT was applied. No recurrence was seen in this case in view of 18-months follow-up.
Arora et al. reported a series of four cases, in which the tumor originated from a minor salivary gland in three patients and from the parotid deep lobe in one patient. Preoperatively, all the cases were reported as benign with FNAB. Recurrence was seen during the follow-up in three cases and postoperative RT was applied to one of them. It was thought that as the masses had been considered to be benign, the recurrence was related to insufficient surgical margins in the excision during the operation. No distant metastasis was seen in any of the patients.
In a population-based survival study of EMC published in 2018, 468 patients were reported since 1972. The patients comprised 291 females and 177 males. The parotid gland was most involved followed by the submandibular gland at the rate of 9.8%. The T-stage of the primary tumor, nodal grade, distant metastasis, age at diagnosis, and nonsurgical treatments were seen to have a negative effect on survival. The survival rate of the group that received nonsurgical treatments was determined to be statistically and significantly low. In the current case, the tumor was completely removed during a superficial parotidectomy operation. However, because of the close proximity of the tumor tissue to the surgical margin, adjuvant RT was offered to the patient but the patient did not accept the radiotherapy. The patient was followed up for 12 months with no recurrence or distant metastasis.
An extremely interesting result with respect to EMCs was recently published. In the early stage, low/moderate-grade parotid carcinomas, when there was a narrow surgical margin, the results of a monitoring strategy showed a 10-year disease-free survival rate of 96.3%. In three patients who developed recurrence, the diagnosis was low-grade EMC. The surgical margins of these cases were 2, 1, and 3 mm. The authors stated that EMC should be considered as a tumor with a high-risk of recurrence.
EMC is a rarely seen tumor for which the diagnosis and treatment algorithm has not yet been fully defined. Even if these tumors are low-grade, they must be followed up closely in respect of recurrence and distant metastasis. When surgical margins are closed, the treatment options are close follow-up, RT, or total parotidectomy. The decision for the most appropriate treatment approach must be taken with the consideration of the tumor characteristics and patient-related factors.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]