|Year : 2015 | Volume
| Issue : 2 | Page : 106-109
Mucoepidermoid carcinoma of parotid gland: A case report
Jeetendra Purohit1, Vela D Desai2, Rajeev Sharma2, Amit K Sharma1
1 Department of Oral and Maxillofacial Surgery, Jaipur Dental College, Jaipur, Rajasthan, India
2 Department of Oral Medicine and Radiology, Jaipur Dental College, Jaipur, Rajasthan, India
|Date of Web Publication||14-Jul-2015|
D-4, Shastri Nagar, Jaipur - 16, Rajasthan
Source of Support: None, Conflict of Interest: None
Mucoepidermoid carcinoma (MEC) is the most common malignant neoplasm of the major salivary glands, accounting for 15.5% of all cases, benign and malignant. The aim of this article is to report a case of MEC in a 73-years-old male patient who presented with a painless firm fluctuant swelling in left preauricular area. The lesion was thoroughly examined preoperatively, and investigations were carried out. Fine-needle aspiration cytology was done for the lesion and report suggested tumor of the parotid gland. Superficial parotidectomy procedure was done, taking care not to injure the lower division of the facial nerve. Post recovery was uneventful with no defect of facial nerve functions. The histologic picture confirmed that the tumor was MEC of parotid gland. Through the literature reviews of MEC the discussions on prevalence, origin, diagnosis, histological finding, investigation and the modes of treatment are made.
Keywords: Mucoepidermoid carcinoma, salivary glands, superficial parotidectomy
|How to cite this article:|
Purohit J, Desai VD, Sharma R, Sharma AK. Mucoepidermoid carcinoma of parotid gland: A case report. Saudi J Oral Sci 2015;2:106-9
| Introduction|| |
Mucoepidermoid carcinoma (MEC), arises from pluripotent reserve cells of excretory ducts that are capable of differentiating into squamous, columnar, and mucous cells.  Although MEC accounts for <10% of all tumors of the salivary gland, it constitutes approximately 30% of all malignant tumors.  Among them, MEC occurs most frequently in the parotid gland. In 1945, Stewart et al. introduced the term mucoepidermoid to define distinct salivary gland tumor characterized by a mixed pattern of two main cell types: Epidermoid and mucus-producing cells. However, third cell type, intermediate cell, which is not mucous or fully epidermoid, is often present. Subsequent metastases of few of the previously benign tumors have led to all mucoepidermoid tumors being considered carcinoma.  Because of the relative rarity of tumors and remarkable variability in their biological behavior, opinions differ about appropriate classification, grading, and treatment. ,,, Several authors have recommended that mucin containing salivary gland carcinoma be classified as an adenosquamous carcinoma rather than MEC if nuclear anaplasia is pronounced. ,, Although surgery generally is accepted as a primary treatment for MEC, the extent of parotidectomy and indications for neck dissection are not clear. ,,
| Case Report|| |
A 73-years-old male patient with a case of painless firm fluctuant swelling of left preauricular area [Figure 1] of 8 months duration is reported. The lesion was thoroughly examined preoperatively, and investigations were carried out. Patient's history included cataract in both the eyes and history of smoking since 40 years, which he left 2 years back. He denied any fever, chills, or night sweats. On physical examination, a firm, 2.5 cm mass was palpated at the left preauricular region. No lymphadenopathy was present, and all facial nerve function was intact. The results of routine blood tests were within normal limits. Findings on fine-needle aspirations were diagnostic.
Microscopic examination of the tumor revealed moderate cellularity, comprising of malignant epithelial cells, arranged in a papillary pattern, clumps and singly. Some cells show squamoid differentiation. Others show eccentric nucleus, intracytoplasmic vacuoles and prominent nucleoli. Many cells with finely vacuolated cytoplasm are also arranged singly. Cells show pleomorphism, anisonucleosis and abundant cytoplasm. Background shows red blood cells.
Computed tomography demonstrated a mildly enhancing, hyperdense, 2.3 cm × 2.5 cm mass involving left parotid gland.
After providing appropriate consent, the patient was posted for a left superficial parotidectomy.
General anesthesia was achieved with rapid sequence intubation and endotracheal intubation. Local Anesthesia (1% lidocaine with 1:80,000 adrenaline) was given. Subcutaneous injection of the anesthetic is administered over the whole operative field.
A modified Blair incision was given. The incision was made in the preauricular crease including the lesion in a circular fashion around the lesion. The skin flap was raised to the superior, anterior and inferior borders of the gland. The flap was raised under the periparotid fascia. The fascia was included in the skin flap and the gland tissues are exposed. Blunt dissection with hemostat was done, and anterior border of the gland was exposed [Figure 2].
Dissection of the facial nerve and resection of the gland
Stensen's Duct was used as a landmark for the identification of the buccal branches of the facial nerve. The skin flap is pulled by a retractor to expose the protrusion of the anterior border of the gland, where Stensen's duct emanates from the gland onto the masseter muscle, the retromandibular vein was used as a landmark for the identification of the marginal mandibular branch, and the zygomatic arch for the zygomatic branch of the facial nerve.
Once the nerve branch was identified [Figure 3], dissection was done using fine-tipped hemostats to create tunnels in the tissue immediately above the nerve. The bridges of parotid tissue over the nerve are gently cut with a scalpel blade. The dissection displaced the parotid upwards and downwards, and hence, avoiding too deep and narrow tunneling. Great care was exercised to avoid inadvertent entry into the tumor during preservation of the facial nerve. As the bifurcation and main trunk of the facial nerve was exposed, the gland was resected at the posterior border. The parotidectomy was excised with the tumor "en bloc" [Figure 4]. The specimen was sent for histopathological examination.
After removal of the superficial parotid gland and the tumor, the cut surface of the parotid remnant was sutured by absorbable sutures. This achieves hemostasis, and also prevents the development of a salivary fistula. The wound was irrigated with saline and the integrity of the facial nerve was checked. Closed suction drainage was placed and suction tube placed away from the dissected facial nerve to prevent damage to the nerve. The skin flap was replaced, the platysma muscle and subcutaneous tissues were closed with absorbable sutures. Finally, the skin incision was closed using 5-0 nonabsorbable sutures. Closed suction drainage with external pressure by gauze was maintained for 48-72 h [Figure 5].
|Figure 5: Intermediate-grade mucoepidermoid carcinoma with an increased number of epidermoid cells and mild nuclear atypia (h and e)|
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Thereafter, a thin layer of gauze was placed on the wound. The sutures were removed 1-week after operation.
Regular postoperative follow-up of the patient was done, but the patient's survival was not >6 months.
| Discussion|| |
Mucoepidermoid carcinoma is the most frequently diagnosed malignancy of the salivary gland. Among the major salivary glands, the parotid gland is most commonly involved. ,,, MEC has no distinctive cytological characteristic. The tumor is composed of epidermoid and mucin producing cells, which take origin from the duct epithelial lining. The epidermoid cells proliferate in sheets or islands, and keratinizing may occur. When the epidermoid constituent predominates, the histological appearance of the tumor may closely resemble that of squamous cell carcinoma, and it is thus classified as a high-grade MEC tumor [Figure 6] conversely, the presence of mucin-producing cells within a predominantly cystic architecture is regarded as low-grade MEC tumors. The morphological appearance of MEC share similarities to metastatic clear cell renal adenocarcinoma and clear cell bronchogenic squamous carcinoma.  Hence, appropriate work-up of the patient must also include imaging of the lungs and kidneys. One of the most important criteria for measuring the biological behavior and aggressiveness of MEC is cell proliferation. The proliferating cell nuclear antigen expression increases with the grade of malignancy.  Furthermore, mucin expression patterns can be useful for diagnostic and prognostic purposes. Membrane-bound mucins are expressed on the cell surfaces of MEC. Studies have shown that the presence of MUC-1 is related to aggressive tumor, while MUC-4 conferred greater cellular differentiation and better prognosis. , Cytokines have also been studied where over-stimulation of cell growth have been implicated in tumor growth.
| Conclusion|| |
Mucoepidermoid carcinoma can present widely diverse biological behaviors based on the myriad of histological characteristics. MEC is a unique carcinoma as it demonstrates a broad spectrum of aggressiveness from indolent tumors that are cured by surgery alone to aggressive neoplasms that are prone to local invasion, recurrence, and metastasis. Parotid MEC appears to be a highly curable disease. Whatever the treatment modality, MEC patients should be closely followed-up for life to rule out late recurrence. 
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]