Indian Journal of Pathology and Microbiology

CASE REPORT
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


Poonam Rani1, Meeta Singh1, Chetna Mehrol1, Amita Jain Gupta1, Nita Khurana1, Ravi Meher2,  
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

Correspondence Address:
Meeta Singh
K-171, Sarita Vihar, New Delhi - 110 076
India

Abstract

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.



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;61:564-566


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 2019 Jul 15 ];61:564-566
Available from: http://www.ijpmonline.org/text.asp?2018/61/4/564/242999


Full Text



 Introduction



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



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.

Gross

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}{Figure 2}{Figure 3}

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}

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

 Discussion



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



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

Nil.

Conflicts of interest

There are no conflicts of interest.

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