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   Table of Contents      
CASE REPORT
Year : 2017  |  Volume : 3  |  Issue : 3  |  Page : 166-169

Epithelial Myoepithelial Carcinoma of Salivary Glands − A Rare Entity


1 Department of ENT, Northern Railway Central Hospital, New Delhi, India
2 Department of ENT, Maulana Azad Medical College and associated Lok Nayak Hospital, New Delhi, India
3 Royal Pearl Hospital, Trichy, Tamil Nadu, India

Date of Web Publication24-Oct-2017

Correspondence Address:
Divya Gupta
66, Raj Nagar, Pitam Pura, New Delhi 110 034, Delhi
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/mamcjms.mamcjms_46_17

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  Abstract 

Epithelial myoepithelial carcinoma is a rare low-grade salivary gland malignancy of presumed intercalated duct origin comprising <1% of all salivary gland tumors. We report two cases of this carcinoma in middle aged persons, diagnosed as pleomorphic adenoma on cytology but later found out to be epithelial myoepithelial carcinoma on histopathology. More than 24 months post-surgery, patients stay free from tumor.

Keywords: Epithelial myoepithelial carcinoma, pleomorphic adenoma, salivary gland


How to cite this article:
Gupta D, Goyal K, Singh I, Bhatia S. Epithelial Myoepithelial Carcinoma of Salivary Glands − A Rare Entity. MAMC J Med Sci 2017;3:166-9

How to cite this URL:
Gupta D, Goyal K, Singh I, Bhatia S. Epithelial Myoepithelial Carcinoma of Salivary Glands − A Rare Entity. MAMC J Med Sci [serial online] 2017 [cited 2019 Aug 19];3:166-9. Available from: http://www.mamcjms.in/text.asp?2017/3/3/166/217127


  Introduction Top


Epithelial myoepithelial carcinoma is a rare salivary gland tumor that most commonly arises in parotid gland. The initial diagnosis on cytological smears is difficult because of the overlapping morphological and cellular traits, so it is important to be aware of this entity during surgery, because local recurrences are common up to 41% in the absence of taking wide margins during excision.[1] We report here two cases of this uncommon entity to further add to the small pool of existing cases and discuss it in brief for better understanding of its nature.


  Case Reports Top


Case 1

A 55-year-old male, chronic smoker presented to Otorhinolarygology clinic with a complaint of gradually progressing swelling in left parotid region for 20 years with pain. Clinical examination showed a large lobulated well-defined swelling approximately 8 cm × 6 cm in size present in left parotid region with overlying skin stretched. On palpation, swelling was mildly tender with normal temperature, firm-hard in consistency and lobulated with irregular surface. Facial nerve was intact, and there was no significant lymphadenopathy. Fine needle aspiration cytology (FNAC) was suggestive of pleomorphic adenoma. CECT revealed an enlarged left parotid gland with an isodense, homogenously enhancing, mass-involving, superficial lobe [[Figure 1]A]. With the diagnosis of pleomporhic adenoma of parotid gland, patient was taken up for superficial parotidectomy under general anesthesia (GA). Intra-operatively, tumor was found to be involving deep lobe. Because frozen sections could not rule out malignancy, total conservative parotidectomy was performed taking 1.5 cm margins. Postoperatively mild facial paresis was present which recovered subsequently in 5 months. Histopathological examination revealed epithelio-myoepithelial carcinoma (EMC) [[Figure 1]B] and showed positivity with S-100 and cytokeratin. The postoperative period of 2 years is uneventful.
Figure 1: (Case 1) Axial CECT scan (A) showing enlarged left parotid gland with well-defined isodense and near homogenously enhancing mass lesion lateral to retromandibular vein with overlying skin heterogeneity. (B) Histopathological picture showing epithelial myoepithelial carcinoma exhibiting a nodular growth pattern consisting of islands of neoplastic cells separated by fibrous septa. Dark ductal cells (indicated by black arrow) surrounded by cells with abundant clear cytoplasm seen (hematoxylin and eosin stain: 100×)

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Case 2

A 50-year-old female presented to Otorhinolaryngology Outpatient Department with the chief complaint of a progressively increasing painless swelling in right parotid region for 1 year. On examination, a solitary well-defined swelling approximately 3 cm × 2.5 cm was present in the right parotid region pushing the ear lobule upward with normal overlying skin. On palpation, swelling was non-tender, firm, and immobile with hard consistency and smooth surface. There was no cervical lymphadenopathy, and facial nerve was intact. FNAC was suggestive of pleomorphic adenoma. Contrast-enhanced computed tomography (CECT) scan revealed bulky right parotid gland with a hypodense mass involving both deep and superficial lobes [[Figure 2]A and [Figure 2]B]. A diagnosis of pleomorphic adenoma of right parotid gland was made, and the patient underwent a total conservative parotidectomy under GA [[Figure 2]C]. A tumor was found per-operatively adhered to branches of facial nerve; from which it was dissected off, taking 1 cm margins. Postoperatively mild facial paresis was present. Specimen histopathology showed EMC with capsular infiltration and positivity with S-100, cytokeratin and EMA [[Figure 2]D]. The patient is under regular follow-up for the last 2 years after surgery, and her facial nerve functions have recovered completely.
Figure 2: (Case 2) Axial (A) and coronal (B) CECT scans revealed bulky right parotid gland with a hypodense mass involving both deep and superficial lobes, (C) peroperative picture showing tumor dissected from facial nerve branches, and (D) microscopic photograph of specimen showing densely stained ductal cells (indicated by black arrow) surrounded by clear myoepithelial cells (hematoxylin and eosin stain: 400×)

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  Discussion Top


Epithelial myoepithelial carcinoma is a rare salivary neoplasm constituting <1% of all salivary gland carcinomas.[2] Initially recognized by World Health Organisation (WHO) as clear cell monomorphic adenoma, its histopathological myoepithelial component was described first by Donath et al. in 1972 who gave this carcinoma its current terminology.[3]

The histogenesis of EMC is uncertain, and it seems to arise in two different clinical settings: either de novo or in recurrent pleomorphic adenoma, the latter suggesting bidirectional differentiation from a stem cell to form myoepithelial and intercalated ductal epithelial cells. De novo EMC tends to be more aggressive with a shorter history.[4] It may be true in the second case because the history was of very short duration of 1 year.

It is slightly more prevalent in women and occurs in older age group because it has been present in both of our patients, usually in the sixth decade of life. The study of 61 cases by Seethala et al. revealed parotid gland to be the most common site for EMC (62.1%) followed by sinonasal mucoserous glands (10.3%), palate (8.6%) and submandibular gland (8.6%).[5] The history consists of swelling enlarging gradually over months or years. Pain and facial palsy may or may not be present. Radiological appearance of EMC is non-specific and cannot be used to differentiate from other neoplasms.

Diagnosis of EMC on FNAC often yields incorrect diagnosis like in both our cases because of the myriad pattern of cells that makes interpretation difficult and hence, is usually misdiagnosed. It is important to evaluate such cytology smears keeping in mind the differential diagnosis of myoepitheloma, pleomorphic adenoma, monomorphic adenoma, adenoid cystic carcinoma, and polymorphous low-grade adenocarcinoma. The characteristic cytological feature of EMC includes (1) three dimensional cellular aggregates, (2) clear cytoplasm in the peripheral cells, and (3) presence of acellular hyaline material.[6]

EMC is characteristically recognized by its constant featuring of a double layer ductal lining of inner small epithelial cells and outer clear myoepithelial cells on histopathology. On electron microscopy, the inner cells have microvilli along with zymogen granules in considerable numbers. The outer cells form a single layer immediately within the external lamina, archetypal of myoepithelial cells, and contain abundant glycogen and a peripheral band of smooth muscle myofilaments.[7] At times, they appear morphologically indistinct when they can be identified by immunohistochemistry with the myoepithelial component showing coloring to S-100, muscle specific actin antiserum, and the ductal cells showing positivity to low molecular weight cytokeratins.[1]

The relative rarity of this tumor makes it difficult to establish consistent prognostic markers. Histological features of solid growth pattern, nuclear atypia, deoxyribonucleic acid aneuploidy and a high proliferative activity may foretell a worse prognosis.[8] Although the neoplasm is said to run a relatively indolent course, and the histological features appear to be benign, locoregional recurrence is reported to occur in half of the cases, though hematological metastasis occurs very late.[4]

Surgical excision with wide margins is the treatment of choice. Radiation therapy may be considered for tumors where resection involves significant cosmetic or functional deficit. Patients have 5 and 10 years survival rate of about 87.1 and 67.5%, respectively.[1] Neck node dissection may be considered in patients with lymph node positivity in advanced or surgically non-resectable cases along with radio-chemotherapy.[9],[10]


  Conclusion Top


EMC should be considered a malignant tumor with a potential for locoregional recurrence as well as distant metastasis. It is important to excise it completely taking good margins, and a long-term regular follow-up is crucial for younger patients.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Fonseca I, Soares J. Epithelial-myoepithelial carcinoma of salivary glands. A study of 22 cases. Virchows Arch A Pathol Anat 1993;422:389-96.  Back to cited text no. 1
    
2.
Batsakis JG, El-Naggar AK, Luna MA. Epithelial myoepithelial carcinoma of salivary glands. Ann Otol Rhinol Laryngol 1992;101:540-2.  Back to cited text no. 2
[PUBMED]    
3.
Donath K, Seifert G, Schmitz R. Zur Diagnose and ultrastruktur des Tubularen Speichelgangkarzinoms. Epithelial-myoepithelial Schaltstuckkarzinom. Virchows Arch 1972;356:16-31.  Back to cited text no. 3
    
4.
Simpson RH, Clarke TJ, Sarsfield PT, Gluckman PG. Epithelial-myoepithelial carcinoma of salivary glands. J Clin Pathol 1991;44:419-23.  Back to cited text no. 4
[PUBMED]    
5.
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. 5
[PUBMED]    
6.
Carillo R, Poblet E, Rocamora E, Rodriguez-Peralto JL. Epithelial-myoepithelial carcinoma of salivary glands: Fine needle aspiration cytologic findings. Acta Cytol 1990;34:243-7.  Back to cited text no. 6
    
7.
Luna MA, Ordonez NG, Mackay B, Batsakis JG, Guillamondegui O. Salivary epithelial-myoepithelial carcinomas of intercalated ducts: A clinical, electron microscopic and immunocytochemical study. Oral Surg Oral Med Oral Pathol 1985;59:482-90.  Back to cited text no. 7
    
8.
Kasper HU, Mellin W, Kriegsmann J, Cheremet E, Lippert H, Roessner A. Epithelial-myoepithelial carcinoma of the salivary gland − A low grade malignant neoplasm? Report of two cases and review of literature. Pathol Res Pract 1995;195:189-92.  Back to cited text no. 8
    
9.
Yamazaki H, Ota Y, Aoki T, Kaneko A. Lung metastases of epithelial-myoepithelial carcinoma of the parotid gland successfully treated with chemotherapy: A case report. J Oral Maxillofac Surg 2013;71:220-6.  Back to cited text no. 9
    
10.
Politi M, Robiony M, Avellini C, Orsaria M. Epithelial-myoepithelial carcinoma of the parotid gland: Clinicopathologic aspect, diagnosis and surgical consideration. Ann Maxillofac Surg 2014;4:99-102.  Back to cited text no. 10
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