Adenoid cystic carcinoma of the sublingual salivary gland: Case report of a rare clinical entity

Adenoid cystic carcinoma of the sublingual salivary gland: Case report of a rare clinical entity

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Case Report

Adenoid cystic carcinoma of the sublingual salivary gland: Case report of a rare clinical entity Swetha Acharya a,∗ , Venkatesh Annehosur b , Kaveri Hallikeri a , Shraddha K. Shivappa a a b

Department of Oral Pathology and Microbiology, S.D.M College of Dental Sciences and Hospital, Dharwad, Karnataka 580009, India Department of Oral and Maxillofacial Surgery, S.D.M College of Dental Sciences and Hospital, Dharwad, Karnataka 580009, India

a r t i c l e

i n f o

Article history: Received 8 May 2015 Received in revised form 15 June 2015 Accepted 24 June 2015 Available online xxx Keywords: Sublingual salivary gland tumor Adenoid cystic carcinoma Invasion

a b s t r a c t Sublingual salivary gland tumors are very rare and most are malignant. We report a case of sublingual salivary gland tumor in a 48-year-old female presenting with a swelling in the floor of the mouth. Magnetic resonance imaging (MRI) findings suggested it to be a neoplastic mass involving left sublingual salivary gland. Fine needle aspiration cytology (FNAC) features based on matrix material and cells were indicative of Adenoid Cystic Carcinoma (ACC). Surgical excision of the lesion was done and postoperative adjuvant radiotherapy was recommended owing to positive surgical margins and capsular invasion. Microscopy confirmed the diagnosis as ACC displaying diverse patterns, along with neural and capsular invasion. © 2015 Asian AOMS, ASOMP, JSOP, JSOMS, JSOM, and JAMI. Published by Elsevier Ltd. All rights reserved.夽

1. Introduction Salivary gland tumors are uncommon, representing 3–10% of all neoplasms of the head and neck region. Sublingual salivary gland malignancies are extremely rare and account for only 0.3–1% of all epithelial salivary gland tumors [1]. It accounts for only 0.4–2.6% of all salivary gland tumors [2]. Sublingual salivary gland tumors occur most frequently in patients during the sixth decade of life, without gender predilection. Clinically, these tumors present as an asymptomatic mass located in the floor of the mouth, which can be misdiagnosed as intraoral minor salivary gland tumors or as other benign and malignant lesions located in this region [1]. Most of the sublingual salivary gland tumors are malignant; Adenoid Cystic Carcinoma (ACC) and Mucoepidermoid Carcinoma (MEC) are most common [3]. Although ACC and MEC are the most common sublingual tumors, only 2% of all ACCs and 1.6% of MECs are sited in sublingual gland. A large case series of ACCs without a single case in the sublingual gland has been reported [1]. The ACC is a relatively rare epithelial tumor of the major and minor salivary glands, accounting for about 1% of all malignant tumors of the oral and maxillofacial regions [4]. Although it may

夽 Asian AOMS: Asian Association of Oral and Maxillofacial Surgeons; ASOMP: Asian Society of Oral and Maxillofacial Pathology; JSOP: Japanese Society of Oral Pathology; JSOMS: Japanese Society of Oral and Maxillofacial Surgeons; JSOM: Japanese Society of Oral Medicine; JAMI: Japanese Academy of Maxillofacial Implants. ∗ Corresponding author. Tel.: +91 9449621202; fax: +91 0836 2467612. E-mail address: [email protected] (S. Acharya).

arise in any site where mucous glands exist, half of these tumors occur in glandular areas other than the major salivary glands, principally in the hard palate, but they also arise in the tongue and in other areas that are the site of minor salivary glands. Unusual locations include the external auditory canal, nasopharynx, lacrimal glands, breast, vulva, esophagus, cervix, and Cowper glands [4]. The clinical and pathological findings typical of this tumor include slow growth, perineural invasion, potential local recurrence and distant metastasis [4–6]. Histopathologically, ACC presents three patterns: cribriform, tubular, and solid. It is recognized that most ACCs do not occur in “pure” cribriform, tubular, or solid types. Rather, all three patterns can be observed in the majority of the tumors. Generally, tumors are classified according to the histologic pattern that predominates [7]. We report a rare case of cribriform type of ACC involving the left sublingual gland, presenting as a mass in the floor of the mouth.

2. Case report A 48-year-old female presented to our institution with a history of swelling in the left anterior floor of the mouth since 5 months. The swelling was initially small in size and gradually increased to the present size. The swelling was associated with throbbing type of pain since 2 months and burning sensation on eating hot and spicy food. There was no history of difficulty in speech, deglutition, tongue movements, and change in the size of the swelling on having food. The patient had a history of surgery of a swelling in the left mammary gland 25 years back.

http://dx.doi.org/10.1016/j.ajoms.2015.06.006 2212-5558/© 2015 Asian AOMS, ASOMP, JSOP, JSOMS, JSOM, and JAMI. Published by Elsevier Ltd. All rights reserved.夽

Please cite this article in press as: Acharya S, et al. Adenoid cystic carcinoma of the sublingual salivary gland: Case report of a rare clinical entity. J Oral Maxillofac Surg Med Pathol (2015), http://dx.doi.org/10.1016/j.ajoms.2015.06.006

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On extraoral examination, facial asymmetry and deviation in the midline were noted. Left submandibular lymph nodes were palpable and tender. On intraoral examination, a well-demarcated, solitary, sessile swelling in the left anterior floor of the mouth was noted measuring approximately 4 cm × 3 cm, which was oval in shape. The lesion extended anteroposteriorly from 41 to 36, occupying the entire left lingual vestibule (Fig. 1). Mucosa overlying the

Fig. 2. Intraoral photograph depicting the position of the swelling with tongue in movement.

Fig. 1. Intraoral photograph showing a well-demarcated, solitary, sessile swelling in the floor of the mouth.

swelling appeared stretched with an area of bluish discoloration. On palpation, the swelling was firm and non-tender with no discharge. The swelling moved with tongue movements (Fig. 2]). Based on the history, duration, and the clinical presentation, the case was provisionally diagnosed as a ranula of the floor of the mouth, and neoplasm arising from sublingual gland or minor salivary glands of the floor of the mouth was considered as differential diagnosis. Occlusal radiograph was taken to rule out the presence of sialolith. An ultrasound examination revealed hypoechoic soft tissue lesion in the floor of the mouth abutting the tongue. The lesion approximately measured 33 mm × 25 mm, showing internal vascularity of low resistance type and also few cystic components. Fine needle aspiration cytology (FNAC) was employed for further evaluation. On FNAC, smears were cellular and consisted of round to ovoid basaloid

cells arranged in branching structures. Smear revealed branching structures and/or delicate clusters that characterize the cribriform pattern. Small basaloid cells in spherules and cylinders or in cribriform groups were noted (Fig. 3). The cells were uniform with round to oval, angulated nuclei, scant cytoplasm, with high nuclear cytoplasmic ratio. Basaloid cells had scant pale staining cytoplasm and oval to angulated dark nuclei. Basaloid cells surround stromal spheres and cylinders. Stromal fragments were larger, variably sized, acellular and sharply demarcated with smooth edges. Amorphous, hyaline globoid structures were characteristic and the tumor cells were intimately associated with this material (Fig. 4). Matrix-containing tumors were considered such as ACC, Pleomorphic Adenoma (PA), basal cell adenoma/adenocarcinoma, and polymorphous low-grade adenocarcinoma (PLGA). The most important differential is between PA and ACC since the implications for clinical management and prognosis are critical. Fibrillar matrix material with frayed edges with embedded myoepithelial cells and predominance of myoepithelial cells are features of PA. Absence of these features and presence of small basaloid cells arranged as solid clusters/spherules/cylinders with hyalinized, acellular, large stromal fragments, well-defined stromal edges and sharp stromal–epithelial interface were suggestive

Fig. 3. Smear revealed branching structures and or delicate clusters that characterize the cribriform pattern [H&E, 40×]; (A) smear consisting of round to ovoid basaloid cells arranged in branching structures [H&E, 20×]; (B) small basaloid cells in spherules and cylinders or in cribriform groups [H&E, 40×].

Please cite this article in press as: Acharya S, et al. Adenoid cystic carcinoma of the sublingual salivary gland: Case report of a rare clinical entity. J Oral Maxillofac Surg Med Pathol (2015), http://dx.doi.org/10.1016/j.ajoms.2015.06.006

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Fig. 4. (A) Basaloid cells with scant pale staining cytoplasm and oval to angulated dark nuclei [Pap, 40×]; (B) amorphous, hyaline globoid structures are intimately associated the tumor cells [H&E, 4×].

of cribriform and tubular subtypes of ACC. The patient was subjected to magnetic resonance imaging (MRI)-NECK (plain and contrast) to determine the location, extension of the lesion, and nodal status. The MRI findings revealed a well-defined, oval-shaped soft tissue mass in the left sublingual region. The mass was predominantly hypointense on T1W images and hyper intense on T2W images. The mass showed heterogeneous enhancement on contrast study. Hemorrhage, cystic areas, and septations were seen within the mass. The lesion appeared arising from left sublingual gland and the size of the mass was 3 cm (Cranio-Caudal) × 3.3 cm (Anteroposterior) × 2 cm (medio-lateral). There was mild dilatation of the left submandibular gland duct (Fig. 5). The findings favored left sublingual gland neoplastic mass. Submandibular glands space, right sublingual gland, and the floor of the mouth appeared normal on MRI. No cervical lymph nodes were seen. The clinical TNM staging for this neoplasm was categorized as stage II (T2N0M0).

Surgical excision of the lesion with 3 mm modest margin was done under general anesthesia. Frozen tissue sections revealed positive anterior margins. On gross examination, the tumor measured approximately 4 cm × 3 cm × 2 cm, creamish brown in color, firm in consistency, and encapsulated. The tumor appeared as a welldefined mass within the substance of the involved sublingual gland. Interspersed translucent, dark and light areas were noted on sectioning (Fig. 5) were noted on sectioning. Cut surface showed tumor infiltration into and beyond the capsule at areas. Microscopy showed isomorphic tumor cells characterized by dark, deeply basophilic nuclei and scant cytoplasm. The tumor cells were arranged in nests of variable size and shape containing many circular or ovoid spaces imparting the Swiss cheese pattern/Cribriform pattern were evident predominantly (Fig. 6A and B). The spaces contained either faintly basophilic mucinous substance or hyalinized eosinophilic zones. Fibrous to hyalinized

Fig. 5. (A) MRI findings revealed a well-defined soft tissue mass in left sublingual region. Mass appears arising from left sublingual gland with a mild dilatation of the left submandibular gland duct; (B and C) mass showed heterogeneous enhancement on contrast study. Hemorrhage, cystic areas and septations are seen within the mass; (D) gross picture depicting the cut surface of a partially encapsulated tumor showing interspersed translucent, dark and light areas.

Please cite this article in press as: Acharya S, et al. Adenoid cystic carcinoma of the sublingual salivary gland: Case report of a rare clinical entity. J Oral Maxillofac Surg Med Pathol (2015), http://dx.doi.org/10.1016/j.ajoms.2015.06.006

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Fig. 6. Histopathological features of adenoid cystic carcinoma arising in sublingual gland. (A and B) Tumor cells are arranged in nests of variable size and shape enclosing many circular or ovoid pseudo cystic spaces imparting the cribriform pattern [H&E, 4×, 20×]; (C) ductal structures formed by layers of isomorphic, basaloid cells characterize the tubular pattern. Tubules contain an eosinophilic mucoid substance [H&E, 20×]; (D) cystic spaces of varying size and shape containing hyalinized eosinophilic material [H&E, 20×]; (E and F) Small cords of isomorphic tumor cells in a densely hyalinized stroma depicting a single file pattern [H&E, 20×, 40×].

septae divided the tumor into compartments. Single ductal structures formed by layers of isomorphic, basaloid cells characterized the tubular pattern (Fig. 6C). The lumina contained mucinous substance that was faintly eosinophilic. Cystic spaces of varying size and shape containing hyalinized eosinophilic material were noted (Fig. 6D). Small cords of isomorphic tumor cells in a densely hyalinized stroma were noticeable at the periphery of the tumor showing a single file pattern (Fig. 6E and F). Solid growth pattern were noted at areas (Fig. 7A and B). The tumor demonstrated capsular invasion at areas (Fig. 7C). Perivascular (Fig. 7D) and neural invasion were also observable (Fig. 7E and F). Based on the above histologic findings, the case was diagnosed as adenoid cystic carcinoma, cribriform type arising from the left sublingual gland. The most important differential considered was PLGA. Qualities of ACCs that are common with PLGAs included an array of morphologic patterns identified as cribriform, tubular, and solid. The cells were small and basophilic with only minimal pleomorphism and mitotic activity.

But the nuclei of ACC are usually more hyperchromatic and more angular than those of PLGA. Cribriform areas with accumulation of pools of glycosaminoglycans, which are frequent in ACC, are not typical of PLGA. Cytoplasmic staining of PLGA is eosinophilic to amphophilic, whereas that of ACC is very pale to clear staining. PLGA has been established as a distinct type of minor salivary gland adenocarcinoma with characteristic clinicopathologic findings. Owing to the positive frozen anterior margins, capsular and perineural invasion, patient was subjected to adjuvant radiotherapy, and is under follow-up. 3. Discussion Neoplasms of the sublingual salivary glands are very rare and comprise only between 0.5% and 1% of all epithelial salivary tumors and approximately 1.5% of all carcinomas of the major salivary glands. Despite their rarity, approximately 80–90% of sublingual

Please cite this article in press as: Acharya S, et al. Adenoid cystic carcinoma of the sublingual salivary gland: Case report of a rare clinical entity. J Oral Maxillofac Surg Med Pathol (2015), http://dx.doi.org/10.1016/j.ajoms.2015.06.006

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Fig. 7. Histopathological features of adenoid cystic carcinoma arising in sublingual gland. (A and B) Nest of basaloid tumor cells describing a solid growth pattern [H&E, 4×, 20×]; (C) tumor demonstrating capsular invasion [H&E, 4×]; (D) tumor depicting perivascular invasion [H&E, 4×]; (E and F) tumor illustrating perineural and intraneural invasion [H&E, 20×, 40×].

gland tumors are frankly malignant [3]. Clinically, a malignant sublingual salivary gland tumor presents as an asymptomatic submucosal nodule in the floor of the mouth, more exactly in the sublingual space, which can cause some inconvenience [1]. In the present case, the swelling was associated with throbbing pain. Symptoms like pain, difficulties with dental prosthesis adaptation, and tongue numbness are also being reported [3]. Other glandular lesions, neoplastic or nonneoplastic, can also present at the floor of the mouth, such as ranula, inflammatory conditions, benign entity associated with salivary duct system and minor salivary gland tumors [1,3]. Depending on the localization, salivary gland tumors can be diagnosed before surgery by incisional or fine needle aspiration biopsies with high index of accuracy [8], helping the surgeon in the planning of the surgical procedure as done in the present case. When presented with a submucosal mass in the floor of the mouth, imaging to determine its consistency, extent and association with

related structures is prudent prior to biopsy. Imaging studies such as computerized tomography (CT) or MRI are helpful to evaluate the extent of the primary tumor and possible nodal metastasis [3]. To establish the site of origin of a submucous nodule in the floor of the mouth, it is important to distinguish between lesions arising in the sublingual or in the minor salivary glands. Frequently, it is not easy to determine the tumor’s origin based only on clinical features, and it is necessary to correlate with CT computerized tomography and MRI, as well as surgical and histopathologic findings [1], as correlated in this report. On T2 weighted MRI, it is well known that the signal intensity of ACC depends on the histological type, namely that low signal intensity corresponds to the solid type with a poor prognosis and high signal intensity corresponds to either the cribriform or tubular subtypes with better prognosis [2]. On the other hand, some studies reported that the signal intensity of the tumor was not useful in determining malignancy in the salivary gland tumors, whereas

Please cite this article in press as: Acharya S, et al. Adenoid cystic carcinoma of the sublingual salivary gland: Case report of a rare clinical entity. J Oral Maxillofac Surg Med Pathol (2015), http://dx.doi.org/10.1016/j.ajoms.2015.06.006

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the intensity is useful in delineating the tumor margin and estimating the tumor volume [2,9]. In the present case, the mass was predominantly hypointense on T1W images and hyperintense on T2W images. The mass shows heterogeneous enhancement on contrast study. Hemorrhage, cystic areas, and septations were noted within the mass. It could not suggest or give clue toward the tumor type, but could specify the origin, location, and extent. In general, high-grade malignant neoplasms of the salivary gland show ill-defined margins, whereas low-grade malignant and benign neoplasms have well-defined margins [2]. On MRI images, most of malignant salivary gland tumors lacked clearly visible capsules [2]. In this case, the tumor was a well defined oval shaped soft tissue mass in the left sublingual region, giving an impression of sublingual neoplastic mass. On gross examination, the tumor was well encapsulated, cut surface of specimen showed capsular invasion and microscopy revealed destruction of mucous acini laying beyond the capsule, possibly the infiltration of the tumor from major sublingual gland into minor sublingual glands. As the sublingual gland anatomically is not a unit organ, it comprises a large segment (the major sublingual gland) and a group of 8–30 small, independent, and aggregated glands (the minor sublingual glands) [3]. ACC occurs mainly in the intraoral salivary glands, particularly in the palate, and parotid, followed by submandibular, extraoral, and sublingual glands [10]. By reviewing 312 ACCs in major salivary glands, Tomich reported that only seven occurred in the sublingual gland [7]. da Cruz Perez et al., in a study of prognostic factors in head and neck ACCs, reported that out of 129 cases 54 cases were related to intraoral minor salivary glands and 48 cases were involving major glands, of which only 3 cases involved sublingual glands [10]. Microscopically, ACC is a biphasic (composed of ducts and basal/myoepithelial cells) salivary gland malignancy characterized by tubular, cribriform and/or solid growth patterns [11]. Generally, the tumors are classified according to the histologic pattern that predominates [7]. Szanto et al. have defined a three tier grading system which takes into account the histomorphologic pattern and percentage of the solid component. This has been regarded as a useful prognostic indicator. Grade 1 ACCs are well differentiated and composed of tubular and cribriform patterns without solid components; grade 2 ACCs are characterized by a pure cribriform pattern or mixed with less than 30% of the solid areas; and grade 3 ACCs are tumors with marked predominance of the solid pattern [12]. In the present case, predominance of cribriform pattern with small areas depicting tubular, single file and solid were observed. Thus the case reported here was classified as grade II. The optimal therapy for ACC of the head and neck has not been established [5,10]. The choice of therapy is affected by site, stage, histologic grade, and biologic behavior of the ACC [5]. Possible treatments of ACC include four modalities: surgical therapy, radiotherapy, chemotherapy, and combined therapy. Surgical excision with wide margins is the treatment of choice [4]. Postoperative radiotherapy is indicated for tumor close to the base of the cranium with presence of cervical node metastasis, tumors associated with perineural spread, solid histologic type (grade), positive resection margins, local recurrence, and distal metastasis [4]. Regardless of grade, all ACCs are treated with surgery plus irradiation because locally they are aggressive and are all considered “high risk” in terms of local recurrence [11]. Local recurrences are frequent because of the infiltrative growth and perineural spread associated with these tumors [13]. Perineural invasions are characteristic of ACCs and occur in up to 60% of the cases [14]. Surgery is the treatment of choice for malignant sublingual gland tumors, but the type of surgical intervention depends on the extent of the primary tumor itself [3]. The treatment choices become quite complex due to the proximity of the tumor to the

inner cortex of the mandible and submandibular salivary gland. In general, excision of this area along with supraomohyoid neck dissection would be the best approach along with postoperative radiation therapy in selected patients with either close margins or perineural spread [3]. For small tumors restricted to the floor of the mouth, a wide surgical resection has been suggested, including the involved sublingual and also the ipsilateral submandibular salivary gland, because the ductal system is often affected even with limited resection [1]. In tumors larger than 2.0 cm, a more aggressive approach has been recommended [1]. Surgery is the cornerstone of treatment, generally requiring excision with widest possible margins. This is because the tumor cells extend well beyond the clinical and radiographic margins and that the tumor undergoes not only perineural invasion but also perineural spread [15]. But based on the clinical presentation and MRI findings suggesting it as left sublingual gland neoplastic mass without involvement of nearby structures, the treatment in this case was restricted to surgical excision of left sublingual gland with 3 mm modest margin. Regarding the adequacy of resection margins, the presence of lesional tissue within 5 mm of the inked surgical margin places a patient at a nearly equal risk for local recurrence. For a tumor of oral cavity, wider margins (1.0 cm) are optimal [16]. Several authors have recommended postoperative radiation when the resection margins are positive or uncertain [17]. As the tumor was in the sublingual space, the possibility of an intraductal spread of malignant tumor is also possible, even if the lesion demonstrates the features of encapsulation [2]. In the present case, the patient was subjected to postoperative radiotherapy owing to the findings such as positive surgical margins, capsular invasion at areas and neural invasion. Garden et al., in a study on the influence of positive margins and nerve invasion in ACC of the head and neck treated with surgery and radiotherapy, concluded that excellent local control rates were obtained in patients using surgery and postoperative radiotherapy [13]. Some authors also recommend postoperative radiation for all patients with ACC, independently of tumor stage, histologic subtype, perineural invasion, and margin status [17]. The prognosis depends mainly on the histologic type of the tumor and adequate primary surgical treatment [1]. Although the tumors of the sublingual salivary gland are rare, they pose a diagnostic challenge, as they are asymptomatic and mostly malignant. They mimic the tumors arising from the minor or submandibular salivary glands, as all of them can present as a swelling occupying the floor of the mouth. Role of the funding source None. Conflict of interest None. References [1] da Cruz Perez DE, Ramoa Pires F, de Abreu Alves F, de Almeida OP, Kowalski LP. Sublingual salivary gland tumors: clinicopathologic study of six cases. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2005;100:449–53. [2] Saito M, Nishiyama H, Maruyama S, Oda Y, Saku T, Hayashi T. Adenoid cystic carcinoma of sublingual gland involving the submandibular duct. Dentomaxillofacial Radiol 2008;37:421–4. [3] Rinaldo A, Shahab AR, Pellitteri PK, Bradley PJ, Ferlito A. Management of malignant sublingual salivary gland tumors. Oral Oncol 2004;40:2–5. [4] Gondivkar SM, Gadbail AR, Chole R, Parikh RV. Adenoid cystic carcinoma: a rare clinical entity and literature review. Oral Oncol 2011;47:231–6. [5] Bradley JP. Adenoid cystic carcinoma of the head and neck: a review. Curr Opin Otolaryngol Head Neck Surg 2004;12:127–32.

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Please cite this article in press as: Acharya S, et al. Adenoid cystic carcinoma of the sublingual salivary gland: Case report of a rare clinical entity. J Oral Maxillofac Surg Med Pathol (2015), http://dx.doi.org/10.1016/j.ajoms.2015.06.006