Primary adenocarcinoma of the base of tongue: a case report and review of the literature.

Introduction
Primary malignant tumors of the base of the tongue are predominantly squamous cell carcinomas, strongly associated with tobacco and alcohol exposure, and more recently with human papillomavirus (HPV) infection [1]. In contrast, primary adenocarcinomas in this location are exceptionally rare, representing only a very small fraction of oropharyngeal neoplasms [2, 3]. Most cases originate from the numerous minor salivary glands embedded within the lingual base mucosa, although nonsalivary epithelial origins have also been described [4, 5].
Reported variants include polymorphous adenocarcinoma, acinic cell carcinoma, and cribriform adenocarcinoma, the latter increasingly recognized as a distinct clinicopathological entity with a predilection for the tongue base [6–9]. Due to their rarity and heterogeneous biological behavior, clinical presentation is frequently nonspecific, typically involving progressive dysphagia, odynophagia, or referred otalgia, which may lead to delayed diagnosis [8–10].
Accurate diagnosis requires endoscopic evaluation and advanced cross-sectional imaging to define lesion extent and cervical lymph node involvement [10]. Definitive identification relies on histopathology supported by immunohistochemistry (IHC). Cytokeratin profiling, particularly CK7 and CK20 expression patterns, plays a key diagnostic role in distinguishing primary adenocarcinoma from metastatic lesions of gastrointestinal or thyroid origin [4, 11]. HPV surrogate markers such as p16 are also relevant, as HPV-driven oropharyngeal carcinomas display distinct behavior and prognosis [1].
Given the scarcity of available data, optimal treatment strategies are not standardized. However, most published cases favor surgical resection with clear margins as the cornerstone of management, often combined with neck dissection and postoperative radiotherapy in the presence of nodal disease or high-risk histologic features [3, 5, 12–15]. Long-term outcomes remain uncertain due to the limited number of reported cases, emphasizing the value of continued case documentation.
Here, we describe a rare case of primary adenocarcinoma of the base of the tongue in a 59-year-old woman treated with transmandibular resection and bilateral neck dissection followed by adjuvant radiotherapy, and we present a narrative review of the literature to highlight diagnostic challenges, immunohistochemical considerations, and therapeutic strategies.

Case presentation

Patient information
A 59-year-old Moroccan woman, without significant medical or surgical history, presented to our otolaryngology department with a 2-month history of progressive dysphagia predominantly for solids, accompanied by intermittent right-sided referred otalgia. She denied dysphonia, dyspnea, odynophagia, weight loss, fever, or other constitutional symptoms. There was no history of smoking, alcohol consumption, radiation exposure, or familial malignancy.

Clinical findings
Oral cavity examination was unremarkable, with no visible lesions on the mobile tongue or oropharyngeal mucosa. Flexible nasofibroscopy revealed an exophytic, firm, erythematous mass arising from the right base of the tongue and partially occupying the vallecula, with well-defined but infiltrative margins. No extension to the mobile tongue, epiglottis, aryepiglottic folds, or tonsillar fossa was observed. Palpation identified a firm, mobile, tender lymph node in the right level II cervical region, with no other cervical masses or cranial nerve deficits (Fig. 1).

Diagnostic assessment
Magnetic resonance imaging (MRI) demonstrated a 28 × 19 mm heterogeneously enhancing mass originating from the right base of the tongue and extending superiorly into the ipsilateral vallecula, without invasion of the mobile tongue or deep extrinsic muscles. Multiple right-sided level II lymph nodes were noted, the largest measuring approximately 12 mm in short axis, suggestive of metastatic involvement. No distant metastasis was identified. A complete metastatic workup was performed, including a computed tomography (CT) scan of the chest, abdomen, and pelvis, as well as positron emission tomography (PET)-CT, all of which showed no evidence of a distant primary tumor or metastatic disease. (Fig. 2).
Panendoscopy performed under general anesthesia confirmed a sessile exophytic lesion confined to the right lingual base. Biopsies revealed an undifferentiated invasive adenocarcinoma. Immunohistochemistry showed strong CK7 and CK20 positivity and p16 negativity, supporting a primary glandular origin unrelated to HPV-driven pathways.
Complete staging classified the tumor as T2N2bM0 according to the AJCC 8th edition.

Therapeutic Intervention
Given the tumor’s location, size, and nodal involvement, a multidisciplinary tumor board recommended primary surgical management. The patient underwent transmandibular surgical resection of the tumor with wide margins, combined with bilateral neck dissection (levels I–IV) and prophylactic tracheostomy. Intraoperative frozen sections confirmed clear surgical margins. A transmandibular approach was selected due to the tumor’s deep posterior extension toward the vallecula, which required wide three-dimensional exposure to ensure complete resection with adequate oncologic margins. A transoral robotic approach (TORS) was not feasible given the depth of the lesion and local technical constraints (Fig. 3A–C).
Postoperative nutritional support was initiated through a nasogastric tube with a high-protein regimen. The patient was decannulated on postoperative day 5, and oral feeding was progressively resumed, with the nasogastric tube removed after 21 days.
Histopathological analysis confirmed complete tumor excision with negative margins. Given the nodal involvement and the high-grade features, adjuvant radiotherapy (total dose: 66 Gy) was administered.

Follow-up and outcomes
The postoperative course was uneventful, with no aspiration episodes or airway complications. The patient experienced gradual improvement in swallowing function and speech clarity with supervised rehabilitation. At 6-month follow-up, clinical examination and imaging demonstrated no evidence of locoregional recurrence or distant metastasis. Functional recovery was satisfactory, with full return to normal oral intake and preserved speech function.

Methods—Narrative review
A literature search was conducted in PubMed, Scopus, and Google Scholar from inception to January 2024.

Search terms
“adenocarcinoma” AND “base of tongue”;
“lingual adenocarcinoma”;
“minor salivary gland tumor” AND “tongue base”;
“cribriform adenocarcinoma tongue”.

Inclusion criteria

Primary adenocarcinoma arising from the base of the tongue

Case reports, case series, or reviews

English or French language

Histologic and immunohistochemical confirmation

Exclusion criteria

Squamous cell carcinoma

Metastatic adenocarcinoma (thyroid, gastrointestinal, lung)

Unknown primary or purely tonsillar origin

Given the rarity of this entity, a qualitative narrative synthesis was performed. A Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)-adapted diagram will be provided in the final submission version.

Discussion
Primary adenocarcinoma of the base of the tongue (BOT) is exceptionally rare, as squamous cell carcinoma remains the predominant histologic subtype in this region [1]. Adenocarcinomas represent only a small fraction of oropharyngeal malignancies [2, 3], and their scarcity contributes to the absence of standardized diagnostic and therapeutic guidelines. Most reported cases arise from the numerous minor salivary glands embedded within the lingual base mucosa [4, 5], although nonsalivary epithelial adenocarcinomas—recently categorized as primary adenocarcinomas of the base of the tongue (PABOTs)—have also been described [16].
Given the undifferentiated morphology of our tumor and its CK7+/CK20+ immunophenotype, the lesion is best classified as a high-grade salivary gland carcinoma, not otherwise specified (NOS). However, its immunohistochemical profile and anatomical location also place it within the spectrum of recently recognized nonsalivary PABOTs, highlighting the diagnostic overlap between these entities.
Histologically, several patterns have been reported, including polymorphous adenocarcinoma, acinic cell carcinoma, and cribriform adenocarcinoma of minor salivary gland origin (CATMSG) [6–9, 17]. First described in 1999 [6], CATMSG was later confirmed as a distinct clinicopathologic entity with consistent architectural and immunohistochemical features [7, 17]. Although considered low-grade, CATMSG demonstrates a notable propensity for cervical lymph node metastasis, reported in up to half of cases [7, 8, 13, 18]. Recent systematic reviews further support this lymphotropic behavior while noting overall favorable disease-specific survival when adequately treated [17, 19, 20].
A summary of previously reported cases, including subtype, IHC profiles, treatment strategies, and outcomes, is presented in Table 1.

Clinically, BOT adenocarcinomas often present with nonspecific symptoms such as dysphagia, odynophagia, and referred otalgia, contributing to diagnostic delay [8–10]. MRI is preferred for assessing BOT tumors due to its superior soft-tissue resolution [10]. Consistent with published data, ipsilateral nodal involvement was present in our patient [7, 12, 13, 15, 18].
IHC is essential in distinguishing primary BOT adenocarcinoma from metastatic lesions. Cytokeratin expression—particularly CK7 and CK20—plays a key role in differentiating primary glandular tumors from metastatic adenocarcinomas of gastrointestinal or thyroid origin [4, 11]. Although CK7+/CK20+ expression may occur in urothelial, pancreaticobiliary, or upper gastrointestinal tumors, this possibility was rigorously excluded in our case through CT of the chest–abdomen–pelvis and PET-CT, both showing no evidence of a distant primary tumor.
The patient’s CK7+/CK20+ phenotype and p16 negativity supported a primary glandular origin and effectively ruled out HPV-related squamous carcinoma [1]. Recent literature emphasizes the importance of integrating IHC with molecular studies when evaluating challenging oropharyngeal adenocarcinomas [17, 18].
Given the absence of universal guidelines, treatment is generally extrapolated from salivary gland and oropharyngeal malignancies. Surgical resection with clear margins remains the primary therapeutic modality [3, 5, 12–15, 19]. For deep or posteriorly extending lesions, a transcervical or transmandibular approach may be required to provide adequate exposure and ensure oncologic clearance [10]. In our case, the transmandibular approach enabled complete access to the vallecular extension and allowed safe oncologic resection. Although transoral robotic surgery has been reported in selected cases, evidence remains limited for BOT adenocarcinomas [18].
Neck dissection is indicated when nodal disease is present or suspected, given the high incidence of cervical metastasis [7, 12, 13, 18]. Adjuvant radiotherapy is commonly recommended for high-risk features—such as nodal involvement, high-grade histology, or perineural invasion—and has been associated with improved locoregional control [3, 5, 14, 19]. Chemotherapy is generally reserved for unresectable or metastatic disease due to limited supporting evidence.
Prognosis varies according to histologic subtype and tumor grade. Low-grade salivary-type adenocarcinomas such as CATMSG typically show favorable outcomes [7–9, 13, 19, 20], whereas high-grade variants may display unpredictable behavior requiring close long-term surveillance [8, 13, 15, 16, 18]. Our patient remains disease-free at 6 months following multimodal treatment, consistent with published outcomes for aggressive therapy in node-positive disease [21].
This case underscores the importance of early recognition of BOT symptoms, comprehensive IHC evaluation, and multimodal treatment in achieving good oncologic outcomes.

Conclusion
Primary adenocarcinoma of the base of the tongue is an exceptionally rare malignancy with poorly defined clinical and pathological characteristics. This case highlights the importance of maintaining a high index of suspicion when evaluating persistent oropharyngeal symptoms and underscores the critical role of endoscopic assessment, advanced imaging, and immunohistochemistry in establishing an accurate diagnosis.
Given the potential for locoregional spread, particularly in high-grade tumors, an aggressive multimodal treatment approach combining surgery, neck dissection, and adjuvant radiotherapy is justified. Our patient’s favorable early outcome reflects the effectiveness of this strategy. However, due to the limited number of reported cases and lack of long-term data, continued surveillance remains essential.
Further accumulation of well-documented cases is needed to refine diagnostic criteria, better understand tumor biology, and develop evidence-based therapeutic guidelines.
Learning Points/Key Clinical Messages.Persistent dysphagia and referred otalgia should prompt early endoscopic evaluation of the base of the tongue.

Immunohistochemistry is essential to distinguish primary adenocarcinoma from metastatic lesions.

Aggressive multimodal therapy (surgery + neck dissection + radiotherapy) may achieve excellent local control in node-positive disease.