Deep lobe parotid gland pleomorphic adenoma

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Case Report

Deep lobe parotid gland pleomorphic adenoma involving the parapharyngeal space Yadavalli Guruprasad, Dinesh Singh Chauhan Department of Oral and Maxillofacial Surgery, AME’S Dental College Hospital & Research Centre, Raichur, Karnataka, India

ABSTRACT

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Pleomorphic adenomas are slow growing, well-demarcated benign neoplasms that constitute more than 80% of benign parotid tumours. Deep lobe parotid pleomorphic adenomas are rare tumors that present a diagnostic and therapeutic challenge. Approximately 10-12% of pleomorphic adenomas of the parotid are thought to arise from the deep lobe of parotid. Due to anatomical relations and restrictive boundaries of the deep lobe, parapharyngeal extensions may remain asymptomatic until reaching a very large size. These tumors have a variety of distinct clinical presentations, most commonly arising from the portion of the gland deep to the facial nerve lateral to the mandible. We present a case of deep lobe parotid gland pleomorphic adenoma involving the parapharyngeal space in a 38 year old female.

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DOI: 10.4103/0975-2870.97518

along with the particular location, increase the difficulty in selecting the best surgical approach to maximize visibility, ensure complete removal of the tumour, and reduce morbidity.[2]

Keywords: Parapharyngeal space, pleomorphic adenoma, salivary gland tumour

Introduction Pleomorphic adenoma is the most common salivary gland neoplasm, accounting for 63% of all parotid gland tumours. Most tumours originate in the superficial lobe but, more rarely; these tumours may involve the deep lobe of the parotid gland,[1] growing medially and occupying the parapharyngeal space. It is generally considered to be a benign tumour, even if this lesion presents several histological features due to the different compounds with a myxoid or chondroid matrix.[1,2] The main characteristics are the high recurrence rate and not infrequent malignant conversion. Symptoms are usually rare or not significant; in fact, in most cases, the only sign is asymptomatic swelling, that slowly grows in the parotid region without involving the facial nerve, the function of which remains unchanged. Often, onset of a facial nerve deficit, changes in consistency, more rapid growth as well as pain are signs of malignant transformation. The histological variety of this tumour

Tumours located in the parapharyngeal space are relatively rare, and experience in diagnosis and treatment is very limited. Parapharyngeal space is shaped like an inverted pyramid, the base of which is formed by the base of the cranium (small portion of petrosal bone), and the apex defines the joint between the posterior hyoid bone. Here, the styloid process and the associated musculature are also found, as well as the internal carotid artery, the sympathetic chain and the IX and XII cranial nerve pairs.[2,3] We present a case of deep lobe parotid gland pleomorphic adenoma involving the parapharyngeal space in a 38 year old female diagnosed by using MRI scan and cytopathology.

Case Report A 38 year old female patient was referred to department of oral and maxillofacial surgery with a chief complaint of swelling in the left side of the jaw from past one year which had been increasing in size over the last 2 months [Figures 1 and 2]. On further examination, a swelling of around 6 × 3 cm in diameter, of solid consistency, non-mobile, and not painful when palpated, was found in the left mandibular angle and submandibular region. The patient underwent

Address for correspondence: Dr. Yadavalli Guruprasad, Department of Oral and Maxillofacial Surgery, AME’S Dental College Hospital & Research Centre, Raichur – 584 103, Karnataka, India. E-mail: [email protected] 62

Medical Journal of Dr. D.Y. Patil University | January-June 2012 | Vol 5 | Issue 1

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Figure 1: Extraoral view showing swelling over the left mandibular angle and submandibular region

Figure 2: Intraoral view showing swelling in the oropharyngeal region causing dysphagia

Figure 3: MRI coronal scan showing swelling located in the left parapharyngeal space displacing the tongue medially

Figure 4: MRI saggital scan showing swelling located in the left parapharyngeal space displacing the tongue medially thus obliterating oropharynx

Figure 5: MRI axial scan showing extension of swelling from deep lobe of parotid into the left parapharyngeal space displacing the tongue medially and thus obliterating oropharynx

Figure 6: Cytopathhology shows admixed epithelial, myoepithelial and mesenchymal components (H&E ×100)


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MRI which showed a large growth in the deep parotid lobe, extending medially to the parapharyngeal space, provoking medial displacement of the muscles [Figures 3-5]. Extra oral FNAC was performed blindly under local anesthesia which showed admixed epithelial, myoepithelial and mesenchymal components consistent with pleomorphic adenoma [Figure 6].

Discussion Pleomorphic adenoma is the most frequent parotid gland tumour, presenting a high rate of recurrence even if it resembles a benign neoplasm. Due to the few symptoms complained of by the patient and the possibility of extension into a hidden site, such as the parapharyngeal space, they can grow for a long time before being diagnosed, and the potential risk of malignant transformation increases over the years with an incidence of 1-7%. They are generally discovered, during routine physical examination, as an asymptomatic mass. Usually, they appear as a cervical swelling, as in our first two cases, or as an intra-oral mass, as in the third patient. Indeed, they remain silent for a long time and the slow growth does not lead to symptoms even if the tumour is in contact, or displaces, vital structures located in the parapharyngeal space, such as vessels or nerves.[3,4] Diagnostic imaging, such as computed tomography (CT) or MRI, are mandatory: MRI is preferred, on account of its better definition of soft tissue, and provides precise information concerning tumour margins as well as the relationship with the surrounding structures. Much controversy exists regarding the use of FNAC in the diagnostic procedures due to localization of these lesions and their relationship with the vascular and nervous structures, which can be damaged by this kind of examination in that case MRI guide FNAC can be done to avoid complications.[4] In our opinion, FNAC is a reliable procedure that can guide the surgeon and be useful in choosing the right surgical approach,[5,6] even though it would not be the first choice diagnostic tool, but it should be performed following diagnostic imaging in order to exclude a vascular lesion. Depending upon the location of the lesion, it can be performed intra-orally or percutaneously, some authors report that the former is more sensitive and prefer the external approach, guided by imaging to avoid vital structures.[7] In the cases described in the present report, reliable results were obtained also performing FNAC intra-orally. Open neck or trans-oral biopsies should be avoided, since opening the tumour capsule increases the risk of recurrence. The elective treatment of para-pharyngeal space tumours is surgery. Many different approaches have been described in the literature.[8,9] All Authors agree on the need to perform surgery requiring adequate exposure to identify and protect vital structures 64

and ensure complete removal. Approaches involving lateral neck dissection are indicated for large tumours involving the para-pharyngeal space without reaching the deep parotid lobe, but full surgical exposure is impeded by the presence of the mandible. The most frequent is the cervical-transparotid approach, which allows exeresis of the benign lesion with good control on the vascular and nervous structures following dissection of the superficial parotid lobe. Various techniques involving osteotomy of the ramus, the angle or the body of the mandible and some modified techniques have been described.[10] Median mandibulotomy increases surgical exposure, preserves mandibular nerve function and provides adequate control both of the neoplasm and of the cervical vessels. Some authors disagree with this approach as aesthetics are compromised by the labiotomy incision, and it also requires entering the oral cavity and involves salivary contamination of the wound.[10] Imaizumi et al. evaluated the usefulness of using the parotid duct, in addition to the retromandibular vein, for differentiating between superficial and deep lobe parotid tumors on MR images, and showed that the parotid duct criterion is useful for determining the location of parotid tumors.[11] FNAC is a safe, cost effective, quick and easy diagnostic procedure that causes little discomfort to the patient. Fine needle aspiration cytology is a valuable adjunct to preoperative assessment of parotid masses as save, noninvasive procedure, almost without contraindications.[12] The high rate of specifity of FNAC presents low possibility that benign cytological diagnosis of parotid tumors become malignant in final histopathological diagnosis. Preoperative recognition of malignant tumors may help prepare both the surgeon and patient for appropriate surgical procedure.[13] In summary, an exhaustive pre-operative diagnostic algorithm is required before approaching this lesion: MRI provides important information about the location and margins and can guide the surgeon in planning the right approach. FNAC, in our opinion, is mandatory to avoid any histological surprise.

References 1. 2. 3. 4. 5.

Berdal P, Hall JG. Parapharyngeal growth of parotid tumours. Acta Otolaryngol Suppl 1969;263:164-6. Carr RJ, Bowerman JE. A review of tumours of the deep lobe of the parotid salivary gland. Br J Oral Maxillofac Surg 1986;24:155-68. Yousem DM, Sack MJ, Scanlan KA. Biopsy of parapharyngeal space lesions. Radiology 1994;193:619-22. Olsen KD. Tumors and surgery of the parapharyngeal space. Laryngoscope 1994;104 Suppl 63:S1-28. Rodriguez-Ciurana J, Rodado C, Saez M, Bassas C. Giant



parotid pleomorphic adenoma involving the parapharyngeal space: Report of a case. J Oral Maxillofac Surg 2000;58:1184-7. 6. Ruiz-Laza L, Infante-Cossio P, Garcia-Perla A, HernandezGuisado JM, Gutierrez-Perez JL. Giant pleomorphic adenoma in the parapharyngeal space: Report of 2 cases. J Oral Maxillofac Surg 2006;64:519-23. 7. Bass RM. Approaches to the diagnosis and treatment of tumors of the parapharyngeal space. Head Neck Surg 1982;4:281-9. 8. Batsakis JG, Sneige N. Parapharyngeal and retropharyngeal space diseases. Ann Otol Rhinol Laryngol 1989;98:320-1. 9. Morita N, Miyata K, Sakamoto T, Wada T. Pleomorphic adenoma in the parapharyngeal space: Report of three cases. J Oral Maxillofac Surg 1995;53:605-10. 10. Sergi B, Limongelli A, Scarano E, Fetoni AR, Paludetti G. Giant deep lobe parotid gland pleomorphic adenoma involving the parapharyngeal space. Report of three cases and review of the diagnostic and therapeutic approaches. Acta Otorhinolaryngol

Ital 2008;28:261-5. 11. Imaizumi A, Kuribayashi A, Okochi K, Ishii J, Sumi Y, Yoshino N, et al. Differentiation between superficial and deep lobe parotid tumors by magnetic resonance imaging: Usefulness of the parotid duct criterion. Acta Radiol 2009;50:806-11. 12. Ciecior E, Sowa P, Adamczyk-Sowa M, Wolny A, Mrowka-Kata K. Huge pleomorphic adenoma of deep lobe origin in the parotid gland. Otolaryngol Pol 2009;63:87-8. 13. Attilio CS, Paolo C, Pierantonio B, Marco C. Usefulness of fine-needle aspiration in parotid diagnostics. Oral Maxillofac Surg 2009;13:185-90.


How to cite this article: Guruprasad Y, Chauhan DS. Deep lobe parotid gland pleomorphic adenoma involving the parapharyngeal space. Med J DY Patil Univ 2012;5:62-5. Source of Support: Nil. Conflict of Interest: None declared.

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