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An Official Publication of the Indian Association of Oral and Maxillofacial Pathologists

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Year : 2023  |  Volume : 27  |  Issue : 5  |  Page : 52-55

Basal cell adenoma of the floor of the mouth masquerading as ranula- A rare case in an unusual location

1 Department of Oral and Maxillofacial Surgery, SMBT Institute of Dental Sciences and Research, Dhamangaon, Ghoti, Nashik, Maharashtra, India
2 Department of Oral Pathology and Microbiology, MGV's KBH Dental College and Hospital, Nashik, Maharashtra, India

Date of Submission24-Aug-2022
Date of Acceptance11-Oct-2022
Date of Web Publication04-Feb-2023

Correspondence Address:
Nilima Prakash
Department of Oral Pathology and Microbiology, MGV's KBH Dental College and Hospital, Nashik, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jomfp.jomfp_356_22

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A 65-year-old female patient with a history of wearing a denture for 15 years reported with a complaint of pain in the floor of the mouth. On examination, a swelling measuring about 2.2 X1.2 cms was noted in the floor of the mouth on the left side. The lesion was excised under local anesthesia. Histopathology revealed a cystic lesion with basaloid cells arranged in tubules, nests and cribriform pattern. A diagnosis of basal cell adenoma was made and confirmed by immunohistochemistry. We report a rare case of Basal Cell Adenoma of the floor of the mouth which mimicked a ranula. The predominantly cystic nature of this basaloid tumor posed a diagnostic challenge. Histopathological and immunohistochemical analysis to arrive at a definitive diagnosis aid in treatment planning and prognostication.

Keywords: Basal cell adenoma, cystic, floor of mouth

How to cite this article:
Gadkari SN, Harnekar S, Mahajan AM, Prakash N. Basal cell adenoma of the floor of the mouth masquerading as ranula- A rare case in an unusual location. J Oral Maxillofac Pathol 2023;27, Suppl S1:52-5

How to cite this URL:
Gadkari SN, Harnekar S, Mahajan AM, Prakash N. Basal cell adenoma of the floor of the mouth masquerading as ranula- A rare case in an unusual location. J Oral Maxillofac Pathol [serial online] 2023 [cited 2023 Mar 21];27, Suppl S1:52-5. Available from: https://www.jomfp.in/text.asp?2023/27/5/52/369179

   Introduction Top

Basal cell adenoma (BCA) of the salivary glands are rare benign tumors occurring mainly in the parotid gland (80%)[1] followed by locations like the upper lip, buccal mucosa, lower lip, and palate.[2]

Basal cell adenomas pose a diagnostic dilemma because of their similarity with other lesions containing basaloid cells. The first case of basal cell adenoma in American Literature was reported by Batsakis in 1972.[3] There is only one reported case of this tumor on the floor of the mouth[4] and this article reports the second case in this unusual location.

   Case Report Top

A 65 year old female patient came with a complaint of pain below the tongue on the left side for the last 3-4 months. The patient was a denture wearer for 15 years. The pain was intermittent on chewing with dentures [Visual Analog Scale (VAS)- 6]) and was relieved on denture removal. The patient denied a history of trauma to the same region. Examination revealed a solitary diffuse fluctuant swelling present in the floor of the mouth of the same color as normal mucosa with a blue hue which was non-pulsatile and non -compressible. There was mild tenderness on palpation (VAS 2), and no local rise in temperature. The submental and submandibular lymph nodes did not show any enlargement on clinical and radiological examination. The patient was a known case of hypothyroidism, diabetes, and hypertension for the last 10–12 years and was on medication for the same.

The ultrasonography findings revealed a well-defined swelling with a thin cystic wall measuring 2.2 × 1.2 cm within the submandibular triangle on the left side with a single septum and low-level echoes within. The submandibular gland appeared normal.

A provisional diagnosis of ranula appeared likely.

Differential diagnosis was benign or malignant salivary gland neoplasm arising from minor salivary glands or epidermoid cysts.

Intra-operative findings- The Patient was administered Inj. Amoxicillin and clavulanic acid 1.2 gm IV, Inj. Paracetamol 500 mg IV, Inj. Pantoprazole 40 mg IV and IV fluids in the perioperative period. Surgical excision of the lesion was carried out under local anesthesia uneventfully [Figure 1].
Figure 1: Intraoperative view of the lesion

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A gross examination of the tissue revealed two cystic cavities filled with chocolate brown material and separated by a fibrous septum [Figure 2]. H & E stained section showed large cystic spaces filled with eosinophilic material and numerous RBCs and foamy macrophages. The cystic spaces were lined by 2–3 layers of cuboidal cells which showed focal thickening at places. The tumor cells were arranged in tubules, strands, islands, and cribriform patterns surrounded by a hyalinized connective tissue stroma. The neoplastic cells were cuboidal with hyperchromatic nuclei and minimal amphophilic cytoplasm suggestive of basaloid cells. These cells were surrounded by thick basement membrane-like material. In a cribriform pattern, eosinophilic coagulum was seen in pseudocysts spaces. Areas of squamous differentiation in the form of whorls and eddies are seen. Numerous blood vessels of varying shapes and sizes were noted. Moderate chronic inflammatory cells infiltrate chiefly lymphocytes and plasma cells seen and cholesterol clefts were noted [Figure 3], [Figure 4], [Figure 5]. The lesional tissue was surrounded by a fibroadipocytic capsule. To arrive at a definitive diagnosis, IHC was performed. Reactivity with Calponin showed focal cytoplasmic positivity in the peripheral cells. Ki67 was weakly positive suggestive of a non-proliferative tumor and ruled out malignancy [Figure 6]. Thus, confirming the diagnosis of Basal cell adenoma.
Figure 2: Gross examination revealed two cystic cavities filled with chocolate brown material separated by a fibrous septum

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Figure 3: (a): Cystic cavity filled with eosinophilic material surrounded by a fibroadipocytic cystic wall. (H&E stain x40); (b): Cystic cavity lined by basaloid cells and tumor islands within capsule arranged in jigsaw pattern. (H&E stain x100)

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Figure 4: (a): Cystic cavities lined by 2-3 layers of basaloid cells showing focal thickenings at places (H&E stain x100); (b): Pseudocystic spaces lined by basaloid cells and containing eosinophilic material. (H&E stain x400)

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Figure 5: Tumour nests surrounded by acellular hyalinized stroma – membranous type (H&E stain x400)

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Figure 6: (a) Focal cytoplasmic positivity for Calponin in the peripheral cells.(IHCx100); (b) Weakly positive for Ki 67 suggestive of non-proliferative tumour (IHCx100)

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   Discussion Top

According to the IARC WHO Classification of tumors, BCAs account for 1 -3.7% of all salivary gland tumors and are most frequently seen in elderly adults with the average patient age at presentation ranging from 57 years to >70 years, with a slight female predilection.[5]

The majority of BCA cases arise in the major salivary glands, but minor salivary gland origin is rare. The most common site of occurrence is the superficial lobe of the parotid gland, while the minor salivary gland is a rare location. The upper lip, buccal mucosa, lower lip, and palate are the sites for the minor salivary gland origin of this tumor.[6] A thorough review of the literature has revealed only five cases of BCA in the submandibular gland,[1] rarely in the sublingual gland[7] and one in the floor of the mouth.[4]

Cytologically small basaloid-type epithelial cells with bland oval nuclei, fine chromatin, indistinct nucleoli arranged in sheets, trabeculae, and nests along with bare nuclei are seen. Two cell populations may be seen- cells with larger nuclei and moderate cytoplasm and a second population with dark nuclei and scant cytoplasm.[8]

It has been proposed that this tumor could form part of a continuum of benign salivary gland tumors, also including pleomorphic adenoma and myoepithelioma since it is composed of a variable admixture of basal, ductal, and myoepithelial cells.[9]

These tumors show a mixture of solid, trabecular, tubular, and membranous patterns and are composed of basaloid cells with scant cytoplasm, indistinct cell borders, and round to oval nuclei, and may show peripheral palisading. Large cells with paler-staining nuclei may be present in the center of the basaloid nests.[5] The membranous pattern features prominent hyaline material, with intercellular coalescing droplets within tumor nests which were noted in the present case.

A frequent overlap of microscopic features among various salivary gland neoplasms and sometimes even between benign and malignant lesions causes a diagnostic dilemma that sometimes may even not be resolved by immunohistochemical studies.[10] It is important to distinguish this lesion from others containing basaloid cells. The features that distinguish this tumor from basal cell adenocarcinoma are an infiltrative growth pattern, cellular atypia, areas of necrosis, profuse mitoses, and neural or vascular invasion[11] all of which were not present in this patient. Furthermore, this lesion was a basal cell adenoma with cystic degeneration.

Ki67 and p63 are expressed intensely in case of basal cell adenocarcinoma, basaloid squamous cell carcinoma, and Adenoid cystic carcinoma,[12] however, in this case, Ki-67 expression was weakly positive thereby ruling out malignancy.

Further, our case showed good circumscription, lack of infiltrative properties, and absence of myoepithelial marker -calponin in the cells around the cribriform spaces which are the most reliable points for differential diagnosis of BCA from Adenoid cystic carcinoma.[13]

The prognosis is usually very good, with a very low recurrence rate, except for the membranous type, which has a recurrence rate of ~25%. Basal cell adenocarcinoma transformation of BCA occurs rarely, with a higher frequency in the membranous type.[5]

   Conclusion Top

This report describes a rare case of Basal cell adenoma in the floor of the mouth which was predominantly cystic in nature. The occurrence of this tumor in the minor salivary glands is infrequent and its occurrence on the floor of the mouth is even rarer. The clinical presentation of this case was similar to a ranula; however, histopathology and immunohistochemistry aided in its diagnosis as a Basal cell adenoma. It is imperative to correctly diagnose this tumor since basal cells containing tumors vary widely in their prognosis.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.

   References Top

Lambade PN, Rajkhokar D, Lambade D. Basal cell adenoma of submandibular salivary gland: A case report and literature review. J Maxillofac Oral Surg 2015;14:999-1003.  Back to cited text no. 1
Bhagat Singh AD, Majumdar S, Ghosh AK, Gandi L, Choudaha N, Sharma I, et al. Basal cell adenoma clinicopathological, immunohistochemical analysis and surgical considerations of a rare salivary gland tumor with review of literature. Niger J Surg 2015;21:31-4.  Back to cited text no. 2
Seifert G. The World Health Organization's histological classification of salivary gland tumors: A commentary on the second edition. Cancer 1992;70:379-85.  Back to cited text no. 3
Prabhu R, Kumar N, Sadhu S, Shenoy R, Vaidya K. Basal cell adenoma of the salivary gland: Cribriform type, a rare case with review of literature. Arch Clin Exp Surg 2016;5:246-9.  Back to cited text no. 4
El-Naggar AK, Chan JKC, Grandis JR, Takata T, Slootweg PJ. WHO Classification of Head and Neck Tumours 4th Edition, Volume 9. Lyon: International agency for research on cancer; 2017. (World Health Organization Classification of Tumours).  Back to cited text no. 5
Das P, Niyogi S, Bhuyan SK, Bhuyan R. Basal cell adenoma of the buccal mucosa masquerading as irritation fibroma: A rare case report. Oncol J India 2018;2:55-7.  Back to cited text no. 6
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Sirohi R, Malhotra S, Wadhwan V, Malik S. Basal cell adenoma of sublingual salivary gland: A rare entity. J Oral Maxillofac Pathol 2020;24:404.  Back to cited text no. 7
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Bhat A, Rao M, Geethamani V, Shetty AC. Basal cell adenoma of the parotid gland: Cytological diagnosis of an uncommon tumor. J Oral Maxillofac Pathol 2015;19:106.  Back to cited text no. 8
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  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]


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