Volume 1, Issue 1 (1-2016)                   J Res Dent Maxillofac Sci 2016, 1(1): 17-21 | Back to browse issues page


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Tootoonchian A, Sezavar M, Kahali Asl R, nematollahi Z. Basal Cell Adenoma of the Parotid Gland: A Case Report and Review of the Literature. J Res Dent Maxillofac Sci 2016; 1 (1) :17-21
URL: http://jrdms.dentaliau.ac.ir/article-1-80-en.html
1- Assistant Professor , Oral and Maxillofacial Surgery Dept, Dental Branch of Tehran, Islamic Azad University, Buali Hospital, Tehran, Iran.
2- Assistant Professor , Oral and Maxillofacial Surgery Dept, Dental Branch of Tehran, Islamic Azad University, Buali Hospital, Tehran, Iran. , roozbehkahali@gmail.com
3- Member of Cranio maxillofacial Research center, Islamic Azad Dental University, Tehran, Iran.
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Abstract

Salivary gland tumors are the pathologies of head and neck that can cause many challenging issues in diagnosis and treatment. Most benign tumors occur in parotid glands.  Among them Pleomorphic adenoma is the most common type. Basal cell adenomas are one of the subtypes of monomorphic adenoma that have rare occurrences. Proper diagnosis and clinical evaluation via radiographic views can lead physician to best management of this neoplasia. Many surgical treatment modalities were described in literature from total parotidectomy to just dissecting the tumoral area alone. Extensive surgery will have malfunctional and unaesthetic results due to resecting the parotid gland. One of the best approach for treating the well circumscribed pathologies which are encapsulated with well histologic capsule that provide the best surgical plan for dissection is the extracapsular dissection without invasion to the major gland itself. It has so low morbidities and also is remedy for these pathologies. A rare case of 47 years old female with basal cell adenoma of parotid will describe here.
 
Keywords: Basal cell adenoma, Salivary gland neoplasms, Parotid neoplasms
 

Introduction

Monomorphic adenoma (MA) of salivary glands is a pathologic condition related to salivary glands and differs from pleomorphic adenoma (PA) in clinical and histologic behaviors. Basal cell adenoma (BCA) is one of the subtypes of MA and was first described by Kleinsasser and Klein in 1967, excluding the word MA by WHO in 1991 by “Salivary Glands Tumor Histological Classification” (1). BCA accounts about 2% of all salivary tumors (2), and about 54% of all MA.(3) It is considered as a low-grade malignant tumor with high recurrence rate and good prognosis. The most frequent location is parotid and the other sites are possible like upper and lower lip, palate, buccal mucosa and ever nasal septum.(3,4) BCAs arise 80% arise in major salivary glands and about 70% occur in parotid in average age of 5-7th decades with predominance in women twice men.(1,4-6) Most clinical presentation is painless swelling, detected in self body evaluation by patient. Differential diagnosis of this tumor include PA and adenoidcystic carcinoma (ACC) that makes specific considerations because of various prognosis and treatment plans.
Basal cell adenoma of the salivary gland in an uncommon type of monomorphous adenoma and only few proven cases of basal cell adenoma of the parotid gland have been previously reported. Here we describe case with review of literature and discuss the diagnosis and management of this rare entity.
Case presentation
In April 2012, A 47 year old white female admitted to oral and maxillofacial ward of Buali Hospital, Tehran, Iran complaining of abnormal painless swelling has begun in last 1 year and it is progressively get enlarged in last 3 mouth (Figure 1). Review of her systems did not reveal any systemic disorders. In extraoral evaluation there was a 3 x 3 cm painless mobile non-fluctuant mass below the right earlobe. The superficial skin was quite intact and normal in appearance and did not presented any heat or redness. All facial movements in right side were intact and symmetric. Examination of the parotid duct performed by milking the parotid gland while examining Stenson’s duct intraorally which showed normal secretory function of the gland. No signs or symptoms of infection were present.

Figure 1: A 47 year old patient with painless swelling below the right ear lobe.
In CT-scan evaluation there is a solid single unilateral mass in the superficial of parotid gland (Figure 2). It seems encapsulated and have not any relationship with the parotid itself.
Figure 2: CT-scan evaluation of the patient reveals a solid mass in the superficial part of the parotid gland. Left: Axial view, Right: Coronal view.
Because the patient was afraid of having cancer and spread of the tumor in her body by performing fine needle aspiration (FNA) biopsy, she did not agreed to have FNA biopsy and was determined for the complete excision of the lesion. Our radiologic and clinical evaluation revealed that the tumor is distinct from parotid gland itself and is attached with the gland via a small pedicle (Figure 3).
Figure 3: MRI evaluation revealed that the tumor is distinct from parotid gland. Left: Axial view, Right: Coronal view.
The patient transferred to the operating room for incisional / excisional biopsy according to the intraoperative findings. A curvilinear skin flap raised in a plane immediately above the parotid fascia to periphery of tumor by about 1 cm. Because intraoperative findings showed a capsulated tumor with distinct periphery from the adjacent tissues, the surgeon decided to completely excise the tumor. Blunt dissection around the capsular view of tumor carried out with Metzenbaum scissor and finger dissection (Figure 4). The tumor capsule itself was never opened.
Figure 4: A curvilinear skin flap raised in a plane immediately above the parotid fascia to the periphery of tumor.
Tumor delivered with its total entity and a small vessel leading to tumor was ligated with a 3-0 silk tie suture. The parotid capsule evaluated and was intact (Figure 5). Two layer closure was taken out and pressure bandage dressing was applied immediately after operation.
Figure 5: Tumor delivered with its total entity and a small vessel leading to tumor was ligated with a 3-0 silk tie suture.
The specimen transferred to the pathology laboratory for histopathologic evaluations. The pathologist described the specimen as an encapsulated well-defined creamy gray mass with elastic and rubbery consistency measuring 2.5 x 2.5 x 2 cm. Microscopic evaluation revealed encapsulated benign neoplasm composed of relatively uniform epithelial cells arranged in solid nests with peripheral palisading of nuclei surrounded by thick hyaline bands, tubules and trabeculae (Figure 6). No significant mitotic activity reported. The diagnosis was basal cell adenoma which was negative for malignancy.
Figure 6: Microscopic evaluation revealed benign neoplasm composed of relatively uniform epithelial cells arranged in solid nests with peripheral palisading of nuclei surrounded by hyaline bands, tubules and trabeculae.

 
Discussion

The average incidence per 100,000 person is 4.7 for benign and 0.9 for malignant variants of salivary gland tumors .(7) Ansari studied 130 cases in Iran, pointed out that the common site for benign minor salivary tumor is anterior part of oral floor and palate is for the malignant types. He had cases of MA(2%), all of them in parotid (Canalicular adenoma or BCA).(7) With this rare prevalence of this tumor in the whole population and Iran respectively we decide to report the case and treatment modalities.
BCA has solid, trabecular, tubular and membranous subtypes. The most common subtype is solid. This slow growing capsulated tumor does not exceed more than 3-cm of diameter, firm, mobile and usually without any signs. For diagnosis, biopsy is the most accurate. Some advocated for fine needle aspiration.(3) Origin of BCA is epithelial, probably in the cells of terminal duct.(1) Mesenchymal component or chondromyxoid stroma unlike PA is absent.(4,8) There is an association between the BCA and existence of cutaneous cylindroma, trichoepithelioma or eccrine spiradenoma of scalp.(1,4) Also there was a report of synchronous ipsilateral sebaceous lymphadenoma and membranous BCA of parotid in a 46-year-old man.(9) Unlike to BCA, infiltrative growth, more than 4 mitotic count / 10 HDP and 5% Ki 67 of staining of cells are observed in basal cell carcinoma (BCC). Whirlpool of epithelial cells, dark external cells in stockade fashion and thick basal membrane are observed in ACCs.(4) Basal cell adenocarcinoma (BCAC) differs from BCA by having invasive behavior, more mitotic activity a neural and vascular invasion. Malignant changes to BCAC is rare but reported in 4.3% of BCA (Nagao et al., 1997). Membranous subtype of BCA, accounted for 25% to 37% of all BCA, a hereditary and recurrent, because of multifocal nature impairs complete removal in surgery.(1,6,10) In Immunohistochemical study (IHC), presence of S-100 protein. Smooth muscle actin (SMA) and vimentin can be realized in most of BCA.(10)
 In a European report more of salivary gland tumors are superficial, All of them unilateral.(5) Less than 10 bilateral cases reported in English literatures.(6) BCA was considered to have ‘sharp margins’ means well demarcated from the rest of the parotid gland. Main differential diagnosis for BCA based on MRI are Warthin’s tumor, PA and BCAC.(11) On T2-weighted MRI, intensity of signal is higher than muscle whereas on T1-weighted  tumor is heterogeneously isointense to muscle.(12) Dynamic CT findings are important for identifying benign and malignant parotid tumors. Intensity enhancement was shown in early phase of BCAs which decrease gradually in later phases like Warthin’s tumor. Unlike of BCA, enhancements are shown in delayed phase of CT in PA and malignant tumors.(11) In comparison of BCA with PA, reports show that the Hounsfield unit (H.U) in BCA show more numeric values in which BCA shows mean 46.8 and 91.43 H.U in unenhanced and contrast enhanced CT respectively and PA had 34.35 and 66.06 H.U. A significant difference exists in mean CT attenuation of BCA and PA on either unenhanced or contrast-enhanced images. Strong enhancement after contrast injection and hemorrhagic components in BCA can be in correlation with vascular architecture.(8) Chiu et al. reported the 2 cases with capsular invasion without any CT image positive findings.
More than 93% of benign cases can be identified clinically alone. Most important assessment is made whenever skin flap elevated with palpation and checking its mobility.(13) Three treatment modalities introduced: superficial or total parotidectomy,  partial parotidectomy or extracapsular dissection. In parotidectomy, some complications occur due to damage of seventh Cranial nerve (CN VII=facial nerve). Other disadvantages are sunken defect due to volume loss of soft tissue and Frey syndrome (synd.) as high as 10% in superficial and 30% after total parotidectomy. Extracapsular dissection means removing of only tumor-bearing area of parotid parenchyma and preserving gland. Orabona in 2012 cited that limited extracapsular dissection does not have increased incidence of tumor recurrence and have low morbidities. The advantages are minimal manipulation of CN VII, eliminate the risk of Frey synd., low incidence of tumor spillage and parotidectomy with minimal risk for CN VII can be done if indicated in future.(13-15) No recurrence has been reported up to 10 years follow-up.(14)  Indicated in single and mobile benign superficial mass in lateral lobe. If tumor diameter is more than 3 cm or located parapharyngeally or deep portion of parotid the parotidectomies are taken out. Key of the extracapsular dissection is maintaining retraction of elevated flap.(13,14) High Hypotensive anesthesia is not required because the surgeon is responsible for hemostasis not the anesthesiologist.(13)


Conclusion

Extracapsular dissection of BCA is an alternative and good method to superficial or total parotidectomy in case of superficially located small mobile tumor mass with visually intact capsule.
 
 
Type of Study: Original article | Subject: Oral medicine

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