Adenoid cystic carcinoma of buccal mucosa with extensive hyalinization: A unique case report

Abstract

Adenoid cystic carcinoma (ACC) is a malignant tumor of salivary glands, 50% of which affect the minor salivary glands. ACC is known for its prolonged clinical course, multiple recurrence rates, and delayed onset of distant metastasis. The tumor usually shows one of the three histopathological variants which are cribriform, tubular, or solid pattern. Here we present a case of ACC affecting rightbuccal mucosa which histopathologically showed cribriform pattern with abundant hyalinization. Surgical excision was the only treatment done without any additional modalities and patient is free of disease since 10 years.

Keywords: Adenoid cystic carcinoma, buccal mucosa, salivary glands

How to cite this article:
Naik KL, Shetty P, Hegde P. Adenoid cystic carcinoma of buccal mucosa with extensive hyalinization: A unique case report. Ann Trop Med Public Health 2013;6:571-4
How to cite this URL:
Naik KL, Shetty P, Hegde P. Adenoid cystic carcinoma of buccal mucosa with extensive hyalinization: A unique case report. Ann Trop Med Public Health [serial online] 2013 [cited 2017 Nov 14];6:571-4. Available from: https://www.atmph.org/text.asp?2013/6/5/571/133746
Introduction

Adenoid cystic carcinoma (ACC) is a rare tumor accounting for less than 1% of all head and neck malignancies and 10% percent of all salivary gland neoplasms. [1] 60.6% of all ACC occur in an intraoral site among intraoral salivary gland ACCs, 12.9% occur on buccal mucosa. [2] The tumor extends well beyond the visible and palpable limits of the salivary gland region. This infiltrative capacity is hallmark of ACC. [1] It typically presents as a slow growing submucosal mass/swelling with constant low-grade dull pain and is well-known for infiltration of nerves with following perineural invasion causing paresthesia. [3] They behave differently with slow growth and local invasion with recurrences and metastasis seen many years after treatment. [1]

Case Report

A 48-year-old male patient visited to the department of Oral medicine and Radiology, A.B. Shetty Memorial Institute of Dental Sciences with a chief complaint of painful swelling in the right side of the mouth since 1 month. There was no history of secondary changes associated with the swelling like pus discharge, ulcer or decrease in salivary flow. On extraoral examination, facial asymmetry was seen due to the presence of a solitary, diffuse swelling in the right middle 1/3 rd of the face [Figure 1]. Skin over the swelling was normal and pinchable. Swelling was firm in consistency, with mild tenderness. Lymph nodes were not palpable. On intraoral soft tissue examination, a well defined solitary swelling was noted in the right buccal mucosa measuring 5 × 6 cm extending anteroposteriorly from the level of right mandibular first molar to posterior faucial pillars and superoinferiorly from the level of maxillary buccal vestibule to 1cm below the occlusal plane. Mucosa covering the swelling was slightly corrugated [Figure 2]. On palpation, swelling was slightly tender, firm in consistency and fixed to underlying structures. Right parotid gland duct opening was normal. Conventional Radiographs revealed no involvement of the bony structures. Ultrasonographic examination Showed 2.6 × 2.4 cm rounded hypoechoic mass in the right buccinator region with minimal amount of vascularity [Figure 3]. Magnetic Resonance Imaging (MRI) revealed a well-defined oval mass in the right buccal fat pad and infratemporal fossa, anterior to the lateral pterygoid muscle. The lesion measured 5.1 × 3.4 × 2.2 cm, which was inhomogenously hypointense on T1weighted and inhomogenously hyper intense on T2 weighted images. Superiorly, the lesion was reaching upto the infra orbital fissure. Superiomedially, lateral wall of the maxillary sinus was compressed and scalloped with no obvious erosion. Anterio-superiorly it extended below the maxillary sinus. Inferio-laterally, lesion was compressing the lateral pterygoid muscle anterior to the ramus of the mandible extending upto the subcutaneous fat. No intra cranial/intra orbital extension of the lesion was noted [Figure 4]. Slight perineural thickening of facial nerve was evident. Fine needle aspiration cytology (FNAC) revealed round uniform cells in a background of mucoid stroma. The cells showed scanty cytoplasm with round/oval hyperchromatic nucleus [Figure 5]. There were no atypical cells seen. Diagnosis of benign salivary gland lesion was given. The lesion was excised in toto and was received for histopathological examination. Submitted surgical specimen consisted of a single soft tissue mass with attached mucous membrane. The mass was measuring 3 × 3 × 2 cm [Figure 6]. On fixation the mass was whitish yellow in color with areas of hemorrhage. On sectioning, the cut surface was soft and showed whitish yellow mass with brownish yellow colored areas. Histopathological examination of biopsy specimen showed islands of tumor cells with darkly stained basophilic nucleus and scanty cytoplasm arranged in the form of cribriform pattern with dense fibrous connective tissue septae separating these islands. Abundant areas of hyalinization were noted throughout the lesion. Few tumor cells were forming discrete islands and anastomosing cords within these areas of hyalinization [Figure 7]. An area of peri and intraneural invasion was noted [Figure 8]. Histopathology was suggestive of adenoid cystic carcinoma of the minor salivary gland. Since the surgical margins were free of the disease it was decided not to give any adjuvant therapy. Surgical site healed with restoration of normal mouth opening. Patient had mild degree of facial palsy. He was followed up for 10 year with no signs of recurrence or distant metastasis.

Figure 1: Extraoral photograph showing the swelling in right middle part of the face

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Figure 2: Intraoral photograph showing swelling in the right buccal mucosa

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Figure 3: Ultrasonographic image showing hypoechoic mass in the right buccinator region

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Figure 4: Magnetic resonance imaging (MRI) revealing a well-defined oval mass in the right buccal fat pad which is showed with an arrow

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Figure 5: Photomicrograph of fine needle aspiration cytology revealing round uniform cells in a background of mucoid stroma (Papanicolaou (PAP) stained section, original magnification ×10)

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Figure 6: Photograph of excised surgical specimen showing single soft tissue mass with a part of attached mucous membrane

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Figure 7: Photomicrograph showing tumor cells in cribriform pattern with abundantareas of hyalinization (hematoxylin and eosin (H and E) stained section, original magnification ×5)

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Figure 8: Photomicrograph showing area of peri- and intraneural invasion by the tumor cells (H and E stained section, original magnification ×5)

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Discussion

The World Health Organization defines ACC as a basaloid tumor consisting of epithelial and myoepithelial cells in various morphological configurations, including tubular, cribriform and solid patterns. [4] Present lesion occurred in minor salivary gland of 48 year old man and is similar with previous reports despite of slight female predilection (3:2). [3] ACC clinically presents as a slow growing, firm, unilobular mass. Pain is usually a common and important associated symptom, occasionally occurring before clinical evidence of the disease. Pain is often continuous and dull aching in nature. [5] Ultrasonography and MRI help in assessing the margins and extent of the lesion. Cytological presentation in aspirate characteristically show spherical clusters (balls) of small tumor cells filled with hyaline material. [6] In the present case FNAC was inconclusive as there were no typical features that were suggestive of ACC (including hyaline globules). ACCs are graded according to histological patterns as Grade I, Grade II, Grade III, with Grade I being a combination of cribriform and tubular, Grade II a mixture of cribriform, tubular and solid patterns, and Grade III having only solid pattern. [3],[5] Present case showed cribriform pattern with abundant hyalinization. There was no solid pattern hence classified as Grade I. It also showed perineural invasion which is highly characteristic feature of ACC. The common clinical feature of pain in these patients may be due to perineural invasion. However, it is not a pathognomonic feature of the disease. [2],[5] Histogenesis and morphogenesis of ACC were extensively studied. The component cells such as the ductal and myoepithelial cells might originate from the pluripotent reserve/stem cells. These myoepithelial cells produce the basement membrane material and form psuedocysts which gives rise to the characteristic cribriform pattern, which is most common histological pattern of ACC. Histologically these areas of basement membrane are seen as hyalinized areas. [7] However there are no studies to relate amount of hyalinized areas with the behavior of ACC. From the present case it can be thought that abundant areas of hyalinization in ACC can be a feature of tumor differentiation and can be a indicator of a favorable prognosis. Present lesion was differentiated from polymorphous low-grade adenocarcinoma (PLGAC) by presence of well-developed ductal and cribriform structures and lack of spindle cells and concentric arrangement of individual cells around blood vessels and nerves. The nuclei of ACC were usually more hyperchromatic and more angular than those of PLGAC. Because of presence of abundant hyalinized stroma in the present lesion, the possibility of mixed tumor was ruled out by the absence of myxochondroid derived stromal elements. [8] The present case did not show any features of metastasis, although literature reveals metastasis to lungs, bones, liver, and brain. [1] According to WHO the influence of perineural invasion on survival has been contradictory. It was stated to have no prognostic significance in some studies. Whereas some authors mention that it is a negative survival predictor because of greater tendency for distant metastasis. [2],[4] Various treatment modalities that have been proposed in ACC cases which include surgery, radiotherapy, chemotherapy, and combined therapy. Surgical excision with wide margins is the treatment of choice. [2],[5] We have followed a similar treatment protocol as histopathologically surgical margins were free of tumor. It is a malignancy that reinforces the point that tumor growth rate and metastatic capabilities are independent tumor properties. [1] ACC typically has a prolonged clinical course with distant metastasis occurring late in the disease despite adequate locoregional control. [5],[9] One study discovered that the median time between diagnosis of the primary lesion and detection of distant metastasis was 60 months with a range of 18-120 months. Unlike other malignancies, they usually do not lead to death in the short term but have low long term survival rates. [2]

Conclusion

ACC affecting the minor salivary gland of buccal mucosa is reported. The case showed typical clinical features of ACC. The patient is free of the disease for ten years without any recurrence or distant metastasis despite the tumor being Grade I malignancy. Surgical excision with wide margins is the treatment of choice provided the surgical margins are clear microscopically. Present case showed histopathologically cribriform pattern with abundant hyalinization. Importance of hyalinization as a predictive factor for prognosis and severity of the disease will be better understood when similar cases are studied in a large scale.

References
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8. Sternberg SS. Tumors of salivary gland. In: Diagnostic Surgical Pathology. 3 rd ed. Philadelphia: Lippincott Williams & Wilkin; 1997. p. 867.
9. Giannimi PJ, Shetty KV, Horan SL, Reid WD, Litchmore LL. Adenoid cysic carcinoma of the buccal vestibule: A case report and review of the literature. Oral Oncol 2006;42:1029-32.

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/1755-6783.133746

Figures

[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]

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