Medical Journal of Dr. D.Y. Patil Vidyapeeth

CASE REPORT
Year
: 2015  |  Volume : 8  |  Issue : 6  |  Page : 772--774

Epithelial myoepithelial carcinoma of the parotid gland


Sachin A Badge1, Nitin M Gangane2, Vitaladevnni B Shivkumar2, Satish M Sharma2,  
1 Department of Pathology, Late Shri Baliram Kashyap Memorial Government Medical College, Jagdalpur, Chhattisgarh, India
2 Department of Pathology, Mahatma Gandhi Institute of Medical Sciences, Sevagram, Wardha, Maharashtra, India

Correspondence Address:
Sachin A Badge
Department of Pathology, Late Shri Baliram Kashyap Memorial Government Medical College, Jagdalpur - 494 001, Chhattisgarh
India

Abstract

Epithelial-myoepithelial carcinoma (EMC) is a low-grade malignant tumor of the salivary glands. It is extremely rare neoplasm accounting for <1% of all salivary gland neoplasms. It is most commonly seen in parotid gland, but has also been described in the submandibular gland, minor salivary glands and extra oral sites. It is most commonly seen in females; with a peak occurrence in the seventh decade. We present a case of EMC of parotid gland in a 55-year-old male patient presented with painless swelling of 8 cm × 8 cm in preauricular region since 1-year. There was no history of fever and no palpable cervical lymphadenopathy. Facial nerve function was intact. All other findings in general examination were within normal limit. As EMC is a very rare tumor having high rate of recurrence we must aware of this entity while giving diagnosis on histopathological examination. Surgeons and oncologist must focus on the best treatment approach to prevent the recurrence of this tumor. Wide local excision, followed by radiotherapy remains the treatment of choice.



How to cite this article:
Badge SA, Gangane NM, Shivkumar VB, Sharma SM. Epithelial myoepithelial carcinoma of the parotid gland.Med J DY Patil Univ 2015;8:772-774


How to cite this URL:
Badge SA, Gangane NM, Shivkumar VB, Sharma SM. Epithelial myoepithelial carcinoma of the parotid gland. Med J DY Patil Univ [serial online] 2015 [cited 2020 Dec 1 ];8:772-774
Available from: https://www.mjdrdypu.org/text.asp?2015/8/6/772/169925


Full Text

 Introduction



Epithelial-myoepithelial carcinoma (EMC) of the salivary glands is a rare tumor, accounting for <1% of all salivary gland neoplasm, that arises most commonly in the parotid gland but has also been described in the submandibular gland, minor salivary glands and extra oral sites. [1] It was initially described as a glycogen-rich or clear cell adenoma because of the clear cell component. There is a female predominance, with a peak occurrence in seventh decade. [2] EMC is a low-grade malignant tumor that may commonly recur locally after resection. Distant metastasis rarely occurs. [3] There are only few cases reported in the literature until now. [1],[2],[3],[4],[5],[6]

 Case Report



A 55-year-old male patient presented with painless swelling of 8 cm × 8 cm in preauricular region since 1-year. There was no history of fever and no palpable cervical lymphadenopathy. Facial nerve function was intact. All other findings in general examination were within normal limit. We received a mass along with overlying skin measuring 6.5 cm × 5.5 cm × 4 cm. The cut section showed a gray white appearance with cystic areas and areas of hemorrhage and necrosis. Histopathological examination showed part of normal salivary gland along with a tumor showing lobular pattern with intervening sclerotic stroma [Figure 1]. Each lobule comprised of ductules lined by inner ductal cells with eosinophilic cytoplasm and outer layers of clear myoepithelial cells. These cells were further enveloped on outside by a well-defined basement membrane. Few ductules contained mucin in the lumen [Figure 2]. Some areas showed microcyst formation with papillary projections of tumor cells into the cystic spaces. Areas of necrosis and hemorrhage were seen. Islands of cells infiltrating adjacent connective tissue were also observed. There was no evidence of nuclear atypia or mitotic figures. Periodic acid Schiff (PAS) test was positive for the intraluminal mucin and basement membrane material. In immunohistochemistry, epithelial cells were positive for cytokeratin. Hence, the diagnosis of EMC was given.{Figure 1}{Figure 2}

 Discussion



Epithelial-myoepithelial carcinoma was first described in 1972 by Donath et al. [4] EMC was previously reported under a variety of names, including adenomyoepithelioma, glycogen-rich adenoma, glycogen-rich carcinoma, clear cell adenoma and clear cell carcinoma. EMC was listed in the World Health Organization (WHO) classification as a distinct clinicopathologic entity in 1991. [5] The WHO defined the EMC as a malignant tumor composed of variable proportions of two cell types, which typically form duct-like structures. The biphasic morphology is represented by an inner layer of duct lining, epithelial-type cells and an outer layer of clear, myoepithelial-type cells. The Histogenesis of EMC is uncertain and it seems to arise in two different clinical settings: Either de novo or in a recurrent pleomorphic adenoma suggesting there bidirectional differentiation from a stem cell to form myoepithelial and intercalated ductal epithelial cells. [3] De novo EMCs arise in normal salivary gland, tend to be more aggressive with a shorter clinical history. EMC arises from the intercalated ducts. Some studies have reported that the intercalated duct in the minor salivary gland is lacking or shorter than that in the parotid gland. This may explain why most EMCs occur in the major salivary glands. However, it is unknown why EMCs occur more commonly in the parotid gland than the submandibular gland. This difference may be related to variations in the intercalated ducts in the two sites. [5] This tumor shows female predominance but there are few reports of this tumor in males similar to our case. [6] They present as bulky, bosselated, slow-growing tumors that may become large. Occasionally, pain or facial weakness may be present. The mean tumor size is 2-3 cm, with a range from 1 cm to 12 cm in largest dimension. [7] The lesion may be encapsulated, but the capsule is frequently incomplete and tumor nodules often extend through it. The computerized tomography and magnetic resonance imaging finding of the EMC of parotid gland are nonspecific and EMC cannot be differentiated from more common parotid neoplasm on the basis of its imaging characteristics. Most EMCs show a characteristic nodular or multinodular growth pattern and classic biphasic tubular histology of inner ductal cells with cuboidal epithelium and outer clear myoepithelial cell layers which are enveloped by basement membrane as seen in our case. Mitotic figures are not common. The clear areas are glycogen-positive and stain for PAS and sensitive to diastase. [8] Immunohistochemically, epithelial component is selectively well highlighted by pancytokeratin and epithelial membrane antigen. Myoepithelial component is demonstrated by S100, smooth muscle actin, p63 and vimentin. [9] The newer markers like calponin, caldesmon and smooth muscle myosin heavy chain may be useful tools for identifying myoepithelial cells when myoepithelial cell differentiation is not easily identified on routinely stained sections. [10] Rarely, some EMC may be found in combination with other salivary gland tumors forming hybrid carcinoma or show dedifferentiation. Patients with EMC having tumor diameter of 4 cm or more, solid tumors predominantly composed of clear cells, forming nests and sheets, marked cellular pleomorphism, tumor necrosis; angiolymphatic and perineural invasion have poor prognosis. There is a high reported rate of local recurrence, approaching 50%. Therefore, adequate resection with negative soft-tissue margins is the minimum recommended and necessary therapy. If the tumor is >4 cm in diameter, combined radiotherapy and surgery have been recommended. Radiotherapy may be of benefit in preventing local recurrence. Local spread to lymph nodes has been reported. Distant metastases to kidney, lung, and brain have also been reported, and are usually fatal. [2] The pathologic differential diagnosis includes other clear cell salivary tumors such as clear cell carcinoma, mucoepidermoid carcinoma, acinar cell carcinoma, sebaceous carcinoma, metastatic renal cell carcinoma, clear cell oncocytoma, pleomorphic adenoma and canalicular adenoma.

 Conclusion



Though, EMC is very rare salivary gland tumor, it should not be missed, as under treatment may lead to recurrence and can reduce the survival in such patients. Surgical excision with wide margins followed by radiotherapy remains the treatment of choice for this cancer.

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