Huge Recurrent Mucoepidermoid Carcinoma of Parotid - a Rare Presentation

Abstract

Mucoepidermoid carcinoma is the commonest primary malignant salivary gland tumor in both children and adults and constitutes around 2.8–16% of all salivary gland tumors. There is a wide age range of 3 to 95 years with a mean age of 47 years. We reported a case of 85 years old female patient, who presented to the department of Surgical Oncology, Srinivasan Medical College and Hospital, Trichy, with history of right parotid swelling for past 25 years, who had undergone Superficial parotidectomy 10 years back, followed by recurrence of tumor with huge increase in size, around 20 cm in greatest dimension. Right Completion Radical Parotidectomy with Modified Radical neck dissection type 1 with Cervical Rotation Flap cover was done and histopathological examination of the surgical specimen confirmed as high grade Mucoepidermoid carcinoma. Following surgery, the patient’s outcome is better, uneventful with periodic regular follow-up.

Introduction

         Mucoepidermoid carcinoma is one of the common malignant salivary gland tumor in both children and adults. It is defined by WHO as “a distinctive salivary gland malignancy composed of mucinous, intermediate and squamoid tumor cells forming cystic and solid patterns.”

         About half of Mucoepidermoid carcinoma arises from major salivary glands with 85–88% occurring in parotid gland, 8-13% occur in submandibular gland and 2–4% involve the sublingual gland [1]. The largest tumor reported in the literature was 12 cm in greatest dimension in major glands [2]. It may occur secondary to radiation or chemotherapy during childhood with a latency period of 8 years [3].

         It accounts for 10 to 15% of all salivary gland tumors. There is a wide age range of 3 to 95 years with a mean age of 47 years. Most common presentation of MEC is painless swelling with pressure and discomfort. The diagnosis of MEC is based on H&E staining of tumors or combination of both histopathological and immunohistochemical analysis.

         The largest tumor reported in the literature was 12 cm in greatest dimension in major

salivary glands [2]. We herein presented a case of 85 years old female with a huge parotid swelling and histopathological examination showed as high grade MEC. The post operative condition of the patient was uneventful and is under periodic follow up.

Case Report

          A 85 years old female with good performance status, presented to Srinivasan Medical college and Hospital, Samayapuram, Trichy, with history of right parotid swelling for 10 years duration, insidious in onset, increased in size for the past 4 years (Fig. 1). Previous FNAC done in the past shown as benign mixed Parotid tumor, followed which Superficial Parotidectomy was done and histopathological reports were not available.

Fig. 1.

Clinical presentation and surgical procedures

          After 6 months, the patient developed recurrence of tumor. Due to old age with risk for surgical complications, patient was on regular follow-up with conservative management. Swelling become huge increase in size in the last 4 years and patient could not able to bear the weight of the tumor.

         On examination - swelling of size- 20 × 16 × 7 cm, involving the right parotid region, irregular in shape with bosselated surface, fixed to the underlying structure, firm to hard in consistency and patient had the features of facial palsy suggestive of facial nerve involvement. CECT Face, head and neck was done, showed an ill-defined excrescent heterogeneously enhancing soft tissue density lesion involving the right parotid, posterior cervical and masticator spaces of the neck, infiltrating right Sternocleidomastoid, Masseter, Buccinator and Medial Pterygoid and reaching up to the base of the skull abutting Jugular foramen region and auditory canal. Bone lysis involving the mastoid air cells (Fig. 2).

Fig. 2.

CECT head and neck – ill-defined excrescent heterogeneously enhancing soft tissue density lesion involving the right parotid.

         By these history and radiological findings, clinical diagnosis made was Recurrent Mucoepidermoid carcinoma- Right parotid with clinical stage of T_4aN₀ M₀. Patient was done all routine investigations, with the haematological parameters were within the normal limits. Fine needle aspiration cytology shown increased cellularity with clusters and singly dispersed squamoid cells, mucus cells (Fig. 3) and intermediate cells in a background of blood mixed mucinous material.

Fig. 3.

Smears show round to polyhedral cells with well-defined finely vacuolated cytoplasm- Mucus cells.

         Surgery done was Right completion Radical parotidectomy with modified Radical Neck dissection type 1 with Cervical Rotation flap cover.

Surgical Procedure

         Under GA, patient was put on head and neck position, Elliptical skin incision was made which includes the involved part of skin and maximum uninvolved part of skin over the tumor

was preserved. The tumor dissection was started from inferior aspect at the cervical region, IJV & ICA control had taken. The dissection was performed all around the tumor, IJV and ICA separated from the tumor up to the base of skull and around 5 mm infiltrated tumor tissue was left over the IJV at the level of jugular foramen. MRND Type-I (SAN and SCM removed) was done. The tumor was removed and defect around 10 × 10 cm was closed with redundant part of skin and cervical rotation flap (Fig. 1).

Outcome and follow-up

          After surgery, the postoperative period was uneventful, patient recovered well and was discharged on 15th post operative day. The patient is on regular periodic follow-up.

Following surgery, the specimen was sent to Department of Pathology, fixed in 10% formalin overnight. Cut surface of the mass shows a grey-white solid tumor with focal cystic areas filled with blood mixed mucinous material and areas of necrosis seen (Fig. 4). The sections were stained with routine Hematoxylin & Eosin technique.

Fig. 4.

Cut surface of tumor- grey-white, solid with cystic areas (yellow arrow)

Histopathological Findings

         Sections studied show an infiltrating tumor arranged in anastomosing irregular solid islands, trabeculae, few tubules, nests and in sheets. The tumor composed of polygonal epidermoid cells having moderate nuclear atypia with coarse chromatin, inconspicuous nucleoli, moderate amount of eosinophilic cytoplasm (Fig. 5) admixed with Intermediate cells with round nuclei and large, columnar goblet-shaped mucous cells in a mucinous background. Few macro and micro-cystic spaces lined by epidermoid and mucous cells containing mucinous secretions are noted. In focal areas, spindling of tumor cells are seen. Lymphovascular invasion, perineural invasion and necrosis seen. MF- 8/10 HPF seen.

Fig. 5.

Nests of polygonal epidermoid cells having nuclear atypia, eosinophilic cytoplasm and distinct cell borders (yellow arrow).

         On correlation of these histopathological findings with Brandwein grading system, with total score of 16, the final diagnosis arrived was Mucoepidermoid carcinoma grade 3 with Pathological staging of the lesion was pT₃pN₀.

Possible Differentials

          Since the tumor has epidermoid cells, it mimics Squamous cell carcinoma. But SCC is very rare in primary salivary glands with overt keratinization and intercellular bridges which were absent in our case.

          Sometimes, pleomorphic adenoma with squamous differentiation occurring post FNA changes create confusion with MEC. But PA is a triphasic tumor showing epithelial cells, myoepithelial cells and chondromyxoid matrix which were absent in our case.

         Necrotizing Sialometaplasia have squamous metaplastic cells and necrotic acini looked similar to MEC. But the lobular configuration was maintained in NS but not in MEC and NS lacked cystic pattern with intermediate cells.

Discussion

         MEC was first described by Stewart et al. [4]. It constitutes around 2.8-16% of all salivary gland tumors with age incidence of 0.44 per 100,00 persons [5]. About half of MECs occur in major salivary glands with 85–88% occurring in Parotid gland, 8–13% involving the submandibular gland and 2–4% involving the sublingual gland [1]. Age of presentation of MEC spans from first to ninth decades, peaking at 4th decade of life. There is a slight female predominance with female to male ratio of 3:2 [2].

          It is one of the Radiation induced salivary gland carcinoma seen in atomic bomb survivors of Hiroshima and Nagasaki [6]. This tumor occurs with high frequency among children, who received radiotherapy for leukemia [7]. High grade MEC is associated with facial nerve palsy [8]. The most common symptom is slowly enlarging painless mass for several years. High grade tumors infiltrate into adjacent tissues and associated with distant metastasis. The usual sites of metastasis are the bone and lung.

         MEC arises from the pluripotent reserve cells of excretory ducts capable of differentiating into mucous, intermediate and epidermoid cells. Histopathologically, it is classified into low, intermediate and high grades, more common being the low grade tumors (48%), followed by high grade tumors (38.7%) and least common is the intermediate grade (13.3%).

         Brandwein grading system stratifies MEC into three different grades [9] that includes the parameters like aggressive pattern of invasion, intracystic component < 25%, pronounced nuclear atypia, Lymphatic/vascular space invasion, Bony invasion, Mitosis > 4/10 HPF, Perineural spread and necrosis and graded the tumors using a score of + 2 and + 3 for each parameters with grade 1 tumors having score of zero (none of the parameters), grade 2 tumors have total score of 2–3 (presence of 1 parameter) and grade 3 tumors have total score of ≥ 4 (presence of 2 or more parameters).

          Low grade tumors have many macrocysts and microcysts, many mucinous cells with bland cytological features and few mitosis. High grade MECs have few cysts, few mucinous cells, significant cellular atypia with highly infiltrative growth.

          MEC harbours CRTC1 and MAML2 fusion with about 55% of cases have positive outcome. Fusion positive cases are observed in young patients with decreased recurrence rates. Its frequency is higher in intermediate and low grade tumors than in high grade tumors [10]. Recent studies have shown that gene fusion status do not form an independent prognostic factor [11]. High grade tumors have higher TP53 mutation, HRAS mutations [12] and PIK3CA mutations.

          Tumor cells positive for Cytokeratin, p40/p63. High p40/p63 expression by MEC helps in distinction from mimickers like Oncocytoma and Acinic Cell Carcinoma [13]. Actin and calponin (myoepithelial markers) are negative. MEC also express various membrane-bound mucins like MUC1, MUC4, MUC5AC, MUC5B. High MUC1 expression associated with high histological grade, high recurrence and metastasis rate, reverse is for MUC4 [14].

          High grade MEC of parotid is one of the most common malignant tumours of parotid with good prognosis in patient undergoing R0 resection, even the R2 resection shows better prognosis with post-op adjuvant radiation. So aggressive tumour resection with good flap cover will shows better outcome in these patients.

Conclusion

         We presented a case of High grade MEC with massive size causing pressure symptoms. The five-year survival rate for low grade MEC is 92%, for intermediate grade MEC is 70–83% and for high grade MEC is 22–44%. Mucoepidermoid carcinoma of parotid have better prognosis. So aggressive tumour resection and good flap cover is mandatory for post-op radiation. In huge parotid tumours with skin involvement maximum uninvolved part of skin should be preserved for better coverage of the defect.

Statements and Declarations

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Competing Interests

Nil.