|Year : 2017 | Volume
| Issue : 3 | Page : 166-169
Epithelial Myoepithelial Carcinoma of Salivary Glands − A Rare Entity
Divya Gupta1, Kavita Goyal2, Ishwar Singh2, Shilpee Bhatia3
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 Publication||24-Oct-2017|
66, Raj Nagar, Pitam Pura, New Delhi 110 034, Delhi
Source of Support: None, Conflict of Interest: None
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 2020 Jan 20];3:166-9. Available from: http://www.mamcjms.in/text.asp?2017/3/3/166/217127
| Introduction|| |
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. 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|| |
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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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|| |
Epithelial myoepithelial carcinoma is a rare salivary neoplasm constituting <1% of all salivary gland carcinomas. 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.
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. 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%). 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.
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. 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.
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. 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.
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. Neck node dissection may be considered in patients with lymph node positivity in advanced or surgically non-resectable cases along with radio-chemotherapy.,
| Conclusion|| |
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.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]