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Year : 2018  |  Volume : 61  |  Issue : 4  |  Page : 564-566
Dedifferentiation of oncocytic epithelial–myoepithelial carcinoma to mucoepidermoid carcinoma in parotid gland: A rare case report

1 Department of Pathology, Maulana Azad Medical College and Associated Lok Nayak Hospital, New Delhi, India
2 Department of ENT, Maulana Azad Medical College and Associated Lok Nayak Hospital, New Delhi, India

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Date of Web Publication10-Oct-2018


Epithelial–myoepithelial carcinomas (EMCs) account for <1% of all salivary gland malignancies. Till now, 23 cases of dedifferentiated EMC have been reported to the best of our knowledge. However, dedifferentiation of oncocytic EMC to mucoepidermoid carcinoma is extremely rare. A 38-year-old female presented with right post aural swelling 4 cm × 2 cm in size for 6 months. Surgical excision was carried out, and we received partly skin-covered tissue 5 cm × 2 cm in size. Sections examined showed features of oncocytic EMC dedifferentiating into mucoepidermoid carcinoma. Myoepithelial component showed oncocytic change which was highlighted by p63.

Keywords: Mucoepidermoid carcinoma, myoepithelial carcinoma, oncocytic

How to cite this article:
Rani P, Singh M, Mehrol C, Gupta AJ, Khurana N, Meher R. Dedifferentiation of oncocytic epithelial–myoepithelial carcinoma to mucoepidermoid carcinoma in parotid gland: A rare case report. Indian J Pathol Microbiol 2018;61:564-6

How to cite this URL:
Rani P, Singh M, Mehrol C, Gupta AJ, Khurana N, Meher R. Dedifferentiation of oncocytic epithelial–myoepithelial carcinoma to mucoepidermoid carcinoma in parotid gland: A rare case report. Indian J Pathol Microbiol [serial online] 2018 [cited 2023 Mar 30];61:564-6. Available from:

   Introduction Top

Epithelial myoepithelial carcinoma (EMC) is a low-grade malignant salivary gland neoplasm accounting for 0.4%–1% of all the salivary gland neoplasms.[1] They are most commonly seen in the parotid gland in approximately 60% cases but can also involve minor salivary glands of larynx, palate, paranasal sinuses, and lower respiratory tract.[2] Histologically, it is a malignant tumor with biphasic morphology, represented by inner layer of duct lining epithelial type cells and an outer layer of myoepithelial cells. Oncocytic change in myoepithelial layer of EMC is rarely seen. The transition of the myoepithelial and/or ductal component of EMC into high-grade carcinoma is known as dedifferentiated EMC. It implies transition into a more aggressive carcinoma. As per extensive literature search, 23 cases of dedifferentiated EMC have been reported.[2],[3],[4],[5],[6],[7],[8] However, oncocytic EMC dedifferentiating into mucoepidermoid carcinoma is extremely rare and has never been reported in literature to the best of our knowledge.

   Case Report Top

A 38-year-old female presented with swelling over the right postaural and parotid region for the last 6 months. It had insidious onset, was painless, and was gradually progressive with no complaints of facial nerve weakness. On examination, the swelling was 4 cm × 4 cm in size, well circumscribed, firm in consistency, smooth surface, and its overlying skin appeared normal. Fine-needle aspiration cytology findings were inconclusive, so surgical resection was carried out, not suspecting malignancy.


We received an already cut open tumor tissue along with skin flap measuring 3 cm × 0.5 cm × 0.3 cm, which on cut section showed gray-white area. No normal salivary gland tissue was identified grossly.

Microscopic examination

Sections showed a well-circumscribed tumor which was partially capsulated [Figure 1]. The tumor was present in biphasic pattern blending imperceptibly with each other [Figure 2]a. One of the patterns was comprised of inner cuboidal cell layer and outer myoepithelial layer. Only myoepithelial layer was showing oncocytic change and that was the predominant component comprised of lobules of polygonal cells present in sheets with abundant eosinophilic granular cytoplasm, round nucleus, and single prominent nucleolus [Figure 2]b. These oncocytic cells revealed focal mild-to-moderate pleomorphism surrounded by prominent lymphoplasmacytic infiltrate. Clear cell-type myoepithelial cells were not seen. Both epithelial and myoepithelial components were infiltrating the stroma. Necrosis was absent and occasional mitosis was seen. Capsule was breached at a few places. Other pattern was comprised of nests of squamous cells with presence of interspersed cells having cytoplasmic vacuoles and clearing [Figure 3]a. On special stains, the vacuolated cells were positive for mucicarmine [Figure 3]b and Alcian blue [Figure 3]c suggesting intracytoplasmic mucin, that is, they represented mucinous component of mucoepidermoid carcinoma. Normal salivary gland tissue was present focally at the periphery.
Figure 1: Normal salivary gland parenchyma on the right side, underlying tumor on the left side with capsular invasion (H and E, ×40)

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Figure 2: (a) Tumor showing biphasic pattern. Epithelial islands in small ducts and surrounding myoepithelial cells showing oncocytic change (H and E, ×200). (b) Luminal epithelial cells which are low cuboidal with bland nuclei and outer myoepithelial layer replaced by oncocytic cells showing abundant, granular, and eosinophilic cytoplasm (H and E, ×600)

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Figure 3: (a) Tumor shows nests of squamoid cells with abundant eosinophilic cytoplasm and vesicular nuclei with open chromatin, feature of mucoepidermoid carcinoma. (b) Mucicarmine stain highlighting the mucous cells with pale foamy cytoplasm, distinct cell membrane component of mucoepidermoid carcinoma. (c) Alcian blue stain highlighting the mucous cells of mucoepidermoid carcinoma

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Immunohistochemistry highlighted the biphasic pattern of the tumor. The tumor cells showed cytoplasmic reactivity for smooth muscle actin and vimentin [Figure 4]a and nuclear reactivity for p63 [Figure 4]b in oncocytic cells therefore considered myoepithelial in origin. Epithelial cells did not express these immunostains. However, cytokeratin was positive in the epithelial cells [Figure 4]c, squamous cell nests, and mucinous cells while negative in myoepithelial cells.
Figure 4: (a) Smooth muscle actin showed positivity for myoepithelial cell layer and negative for epithelial layer. (b) p63 nuclear positivity in myoepithelial cell layer which is showing oncocytic change and epithelial cells are negative. (c) Immunohistochemistry picture of cytokeratin positivity in epithelial cell layer and faint positivity in myoepithelial cell layer

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Hence, on the basis of morphology, special stains, and immunohistochemistry, a diagnosis of oncocytic EMC dedifferentiating to mucoepidermoid carcinoma was given.

   Discussion Top

EMC is a rare entity accounting for only 1%–2% of all and 2%–5% of malignant salivary gland tumors.[9] It is a rare low-grade malignant tumor involving mainly the parotid gland in 60%–75% cases but can also involve minor salivary glands.[2] This tumor occurs commonly in sixth to seventh decade with predilection more for females. It is a moderately aggressive tumor with a recurrence of about 40% after excision. Metastasis can occur to lymph nodes, lung, and liver, although distant metastasis is rare. It has several morphological variants, oncocytic, apocrine, double clear, sebaceous EMC, and EMC ex-pleomorphic adenoma. Oncocytic and apocrine EMC together contributes to 8% of all EMC.[10]

EMC can progress in two types. One is progression to high-grade tumor with more solid pattern, more mitosis, and more atypia, while the second is dedifferentiation to another tumor. Dedifferentiation traditionally means transformation to higher-grade malignancy. It can dedifferentiate to acinic cell carcinoma, intraductal carcinoma, polymorphous low grade adenocarcinoma, adenoid cystic carcinoma, poorly differentiated adenocarcinoma, and mucoepidermoid carcinoma. Till now, 23 cases of dedifferentiated EMC have been reported to the best of our knowledge.[7],[8] Dedifferentiation usually occurs a decade later than conventional EMC, mostly involves parotid gland, and usually occurs in epithelial than the myoepithelial component.[7]

Our case is extremely rare because of the following findings: dedifferentiation occurred at a very young age, that is 38 years[2] and oncocytic change was present in myoepithelial cells of EMC.[3] Dedifferentiation of EMC into mucoepidermoid carcinoma is extremely rare.

Although classical EMCs are indolent tumors, dedifferentiation results in poor prognosis. Definitive treatment of dedifferentiated EMC is wide local excision, with or without radiotherapy; however, chemotherapy has no role. Hence, early diagnosis of dedifferentiated component is required.

   Conclusion Top

EMCs are rare low-grade carcinomas of the salivary gland. Dedifferentiation in EMC is again rare with only 24 cases reported till date including our case.

Herein, we are presenting this case because of its exclusive features which have never been reported before. Oncocytic EMC dedifferentiating into mucoepidermoid carcinoma is an extremely rare entity and detecting a dedifferentiated component in EMC has a huge prognostic and therapeutic relevance.

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.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

Gnepp D. Diagnostic Surgical Pathology of the Head and Neck. Philadelphia, PA: WB Saunders; 2001.  Back to cited text no. 1
Seethala RR, Barnes EL, Hunt JL. Epithelial-myoepithelial carcinoma: A review of the clinicopathologic spectrum and immunophenotypic characteristics in 61 tumors of the salivary glands and upper aerodigestive tract. Am J Surg Pathol 2007;31:44-57.  Back to cited text no. 2
Alos L, Carrillo R, Ramos J, Baez JM, Mallofre C, Fernandez PL, et al. High-grade carcinoma component in epithelial-myoepithelial carcinoma of salivary glands clinicopathological, immunohistochemical and flow-cytometric study of three cases. Virchows Arch 1999;434:291-9.  Back to cited text no. 3
Yang S, Chen X. Epithelial-myoepithelial carcinoma with high grade transformation. Int J Oral Maxillofac Surg 2012;41:810-3.  Back to cited text no. 4
Nagao T, Sugano I, Ishida Y, Asoh A, Munakata S, Yamazaki K, et al. Hybrid carcinomas of the salivary glands: Report of nine cases with a clinicopathologic, immunohistochemical, and p53 gene alteration analysis. Mod Pathol 2002;15:724-33.  Back to cited text no. 5
Kainuma K, Oshima A, Suzuki H, Fukushima M, Shimojo H, Usami S, et al. Hybrid carcinoma of the parotid gland: Report of a case (epithelial-myoepithelial carcinoma and salivary duct carcinoma) and review of the literature. Acta Otolaryngol 2010;130:185-9.  Back to cited text no. 6
Baker AR, Ohanessian SE, Adil E, Crist HS, Goldenberg D, Mani H, et al. Dedifferentiated epithelial-myoepithelial carcinoma: Analysis of a rare entity based on a case report and literature review. Int J Surg Pathol 2013;21:514-9.  Back to cited text no. 7
Aydın S, Taskin U, Ozdamar K, Yücebas K, Sar M, Oktay MF, et al. Case study of a parotid gland adenocarcinoma dedifferentiated from epithelial-myoepithelial carcinoma. Case Rep Otolaryngol 2014;2014:629054.  Back to cited text no. 8
Ellis GL, Auclair PL. Tumors of the Salivary Glands, Atlas of Tumor Pathology. 4th ed. Washington: ARP press; 2008.  Back to cited text no. 9
Seethala RR. Oncocytic and apocrine epithelial myoepithelial carcinoma: Novel variants of a challenging tumor. Head Neck Pathol 2013;7 Suppl 1:S77-84.  Back to cited text no. 10

Correspondence Address:
Meeta Singh
K-171, Sarita Vihar, New Delhi - 110 076
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/IJPM.IJPM_64_17

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  [Figure 1], [Figure 2], [Figure 3], [Figure 4]


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