Canalicular adenoma: A systematic review

Canalicular-Like Pleomorphic Adenoma of the Parotid Gland: A Recently Classified Tumor Highlighting the Use of Frozen Section Analysis and Surrogate IHC for Gene Rearrangement Defined Subtypes

Canalicular-like pleomorphic adenomas are a relatively recently described entity, that possess features of both canalicular adenomas and pleomorphic adenomas. The presence of unusual HMGA2-fusion partners (most commonly HMGA2::WIF1 gene fusions) has established canalicular-like pleomorphic adenoma as a distinct entity. The use of intraoperative frozen section analysis and surrogate HMGA2 IHC are 2 tools that can provide the surgical team with valuable insight into intraoperative decision making and final classification of rare tumors of the parotid gland, respectively. We present a case of canalicular-like pleomorphic adenoma and characterize its appearance on frozen section analysis. HMGA2 IHC staining was retroactively performed, assisting in the confirmation of the tumor subtype.

Canalicular Adenoma in the Parotid Gland: A Rare Case Study

Canalicular adenoma (CA) is a rare benign tumor of the salivary glands, predominantly affecting elderly females, with a strong predilection for the upper lip. While CA commonly arises in the minor salivary glands, its occurrence in the parotid gland is exceptionally rare. In this report, we present a unique case of CA in the parotid gland, adding to the scant literature with only 8 documented instances. The patient, a 57-year-old Asian male, presented with a painless swelling in the left parotid gland that had been persisting for 8 years. Clinical examination and imaging studies identified a lobulated mass, prompting surgical intervention. The patient underwent a superficial parotidectomy, and pathological examination of the excised tissue confirmed the diagnosis of CA, with no signs of malignancy. This case illustrates the diagnostic and management challenges associated with CA, particularly given its rare presentation in the parotid gland. Accurate diagnosis is reliant on surgical biopsy, and careful surgical planning is imperative, especially considering the proximity of the facial nerve. Our case underscores the need for heightened awareness of CA's unique presentations, particularly within the Asian population. Given the potential for recurrence, long-term follow-up is essential. Further research is needed to elucidate the biological behavior of CA and to refine management strategies for optimal patient outcomes.

An Extremely Rare Case of Synchronous Low-Grade Polymorphous Adenocarcinoma With Canalicular Adenoma of the Minor Salivary Gland of the Palate

Tumors of the salivary gland are a group of complex, heterogeneous lesions that are located either in the parotid gland, submandibular gland, sublingual gland, or minor salivary glands. These tumors have a wide range of etiology, pathophysiology, treatment, and prognosis. Multiple salivary gland tumors are extremely rare and usually occur more commonly in major salivary glands than in minor glands. A 61-year-old man with a chief complaint of swelling in the upper jaw for the past eight years reported to the department of oral and maxillofacial surgery. Incisional biopsy revealed a canalicular adenoma (CA) of the minor salivary gland of the palate. Wide local excision was done with closure using a buccal pad of fat and a collagen sheet. Surprisingly, the excisional biopsy was suggestive of synchronous low-grade polymorphous adenocarcinoma (PAC) with CA of the minor salivary gland of the palate. This appears to be the first reported case of PAC with CA found in the palate.

A rare case of canalicular adenoma in the parotid gland: Highlighting diagnostic limitations of fine-needle aspiration

BACKGROUND

Canalicular adenoma is a rare, benign tumor of primarily salivary gland origin that presents mostly in the upper lip. However, there are only six reports in the English literature detailing canalicular adenoma of the parotid gland, none of which discuss discrepancy between preoperative cytology and surgical pathology. In this report, we present a rare case of parotid gland canalicular adenoma where preoperative ultrasound-guided fine-needle aspiration (USFNA) suggested malignancy. The patient was treated with deep lobe parotidectomy due to the FNA results and her multiple comorbidities. However, her tumor may have been treated with observation alone if canalicular adenoma had been suspected prior to surgery.

MAIN FINDINGS

A 59-year-old female with a history of heart and lung disease presented with a 1.6 cm well defined, enhancing lesion involving the superficial portion of the right parotid gland. This lesion was incidentally noted on CT angiography (CTA) of the neck and chest. The well-defined characteristics of this lesion on CT imaging suggested benign neoplasm. However, USFNA results were suggestive of a malignant parotid lesion. The patient subsequently underwent right deep lobe parotidectomy with facial nerve dissection and superficial musculoaponeurotic system (SMAS) rotational flap reconstruction. Surgical pathology and immunohistochemistry yielded a final diagnosis of benign canalicular adenoma.

CONCLUSIONS

USFNA diagnosis of CA is extremely difficult due to its low-grade neoplastic cells mimicking neoplastic cells in other benign and malignant tumors of the head and neck. FNA remains a useful tool for assessing malignancy risk, but the results always have some level of uncertainty and do not provide sufficient detail. Therefore, FNA results should be interpreted in concert with imaging and patients' medical history. Cytopathologists can also report salivary gland FNA results in a more uniform and detailed manner by utilizing the Milan System for Reporting Salivary Gland Cytopathology (MSRSGC).

Canalicular adenoma: palatal presentation of an uncommon lesion

Canalicular adenoma is a unique, rare, benign salivary gland neoplasm whose reported prevalence varies in different studies. According to literature, this neoplasm has a marked predilection to occur in the upper lip of elderly women. Histological features are usually distinctive and diagnostic. This neoplasm has good prognosis after conservative surgical management but the propensity of multifocal nature and recurrence of this lesion mandates regular follow-up. This case report illustrates the case of a canalicular adenoma in the palate in a 71-year-old male patient. Here, we discuss the differential diagnosis with a brief review of literature.

Canalicular adenoma of the tongue: report of a unique case

Canalicular adenoma (CA) is a rare, unique benign salivary gland neoplasm, which usually involves the minor salivary glands of the upper lip, buccal mucosa and palate. It is usually seen in middle-aged or older individuals, has a female predilection, and commonly presents as a painless, slow-growing, non-ulcerated nodule or swelling. Its treatment involves surgical excision or enucleation. This case report describes a case of CA of the ventrum of the tongue diagnosed in a 41-year-old male patient, which could possibly be the first reported case of this lesion involving the tongue.

Synchronous Multifocal Canalicular Adenomas

Canalicular adenoma (CAD) is an uncommon benign tumor of minor salivary glands with predilection for the upper labial mucosa. An 80-year-old female presented with nine submucosal nodules of the upper labial mucosa and bilateral buccal mucosa. Histopathologic examination revealed multifocal circumscribed tumor islands with a tubular growth pattern within a loose hypocellular myxoid background stroma. Interconnecting rows of columnar tumor cells imparted a canalicular morphology. In addition to the characteristic histopathologic findings, a comprehensive immunohistochemical panel supported a final diagnosis of multifocal CAD. Synchronous multifocality in CAD is an infrequent finding and this sine qua non clinicopathologic correlation article exemplifies such a case.

Canalicular adenoma with unicystic morphology. A rare entity

Background

Canalicular adenoma (CA) is a benign salivary gland tumor (SGT) almost exclusively affecting the minor salivary glands, predominantly of the upper lip, and exhibiting characteristic histopathologic features. As observed in several other SGTs, a commonly encountered finding is the presence of prominent cystic morphology. Even though a multicystic appearance is usually noticed, solitary cystic CAs may rarely occur.

Case Report

Two female patients (74 and 78 years old respectively) presented for the evaluation of submucosal asymptomatic masses of the oral cavity. In the 1st case a solitary nodule was noticed in the upper lip, while the 2nd patient exhibited two symmetrical lesions of the buccal mucosae. All three excised specimens displayed cystic morphology upon gross examination. Histopathologically, a solitary cystic formation lined by monomorphic cuboidal or basaloid cells arranged in solid or trabecular patterns was observed in the 1st case. With a differential diagnosis of CA vs basal cell adenoma immunohistochemical examination was performed. Positivity for S-100, CK7 and CD117 (c-kit) and negative reaction for GFAP, p63 and SMA rendered the diagnosis of CA. In the 2nd case both lesions displayed well-circumscribed proliferations by monotonous cuboidal or columnar cells arranged in single cords and occasionally forming beading patterns, while central solitary areas of marked cystic degeneration were noticed. Diagnosis of multifocal unicystic CA was disclosed.

Discussion

To our knowledge, only 11 additional cases of unicystic CA have been reported in the English-language literature. Although the exact clinical significance of unicystic morphology in CA is unknown, a tendency for occurrence within the context of multifocal tumors has been detected.

Key words:Canalicular adenoma, monomorphic adenoma, unicystic morphology, multifocal tumors, minor salivary glands.

Prevalence of mucoepidermoid carcinoma among intraoral minor salivary gland tumors: A systematic review and meta-analysis

This study aimed to synthetize and critically appraise available evidence regarding mucoepidermoid carcinoma (MEC) prevalence among intraoral minor salivary gland tumors (MiSGT). Five main electronic databases and three grey literature databases were searched. The risk of bias (RoB) was assessed using the Joanna Briggs Institute Critical Appraisal Checklist for Studies Reporting Prevalence Data. Proportion meta-analyses were performed. From 1321 studies identified, 82 were included in qualitative synthesis and 80 in meta-analyses. Sixteen were classified as high, 33 as moderate, and 33 as low RoB. A total of 12 774 MiSGT were found, of which overall MEC prevalence was 16.5% (95% Confidence Interval [95% CI] = 14.8%-18.4%). Most MiSGT were found in the palate (n = 7115), although MEC pooled prevalence in this anatomic location was only 13.6% (95% CI = 11.7%-15.6%). The retromolar area presented the highest pooled prevalence (58.9%; 95% CI = 47.0%-70.3%), followed by gingiva (28.8%; 95% CI = 22.7%-35.4%) and tongue (27.2%; 95% CI = 21.2%-33.6%). Regarding geographic location, Middle East presented the highest pooled prevalence (20.8%; 95% CI = 14.8%-27.6%), followed by America (20.0%, 95% CI = 17.2%-23%) and Europe (15.6%; 95% CI = 9.2%-23.5%). Among MiSGT, the MEC overall prevalence was approximately 16.5%. Although most MiSGT were found in the palate, the retromolar area was proportionally more affected by MEC.

Fine-Needle Aspiration Cytology of Cellular Basaloid Neoplasms of the Salivary Gland

Context.—

Cellular basaloid neoplasms of the salivary gland represent a diverse group of benign and malignant neoplasms with significant cytomorphologic overlap on fine-needle aspiration cytology. All are marked by the presence of monotonous and usually bland basaloid epithelium. Distinction between basaloid neoplasms on fine-needle aspiration cytology is based on the presence or absence of additional features, including a second cell population (eg, myoepithelial cells), an acellular stromal component, and/or cytologic atypia within the basaloid epithelium. This review highlights the cytomorphologic features of the most common cellular basaloid neoplasms of the salivary gland, with an emphasis on classification and subclassification within the Milan System.

Objective.—

To provide a comprehensive review of the cytologic features of basaloid epithelial neoplasms of the salivary gland, with an emphasis on classification within the Milan System for Reporting Salivary Gland Cytopathology.

Data Sources.—

Peer-reviewed literature, recent textbooks, and personal experiences of the author.

Conclusions.—

Some basaloid neoplasms, in particular pleomorphic adenomas and adenoid cystic carcinomas, may have characteristic findings on fine-needle aspiration that allow for definitive diagnosis. In other cases, however, fine-needle aspiration can confirm a neoplastic basaloid process, but specific classification of a benign or malignant neoplasm cannot be rendered. The Milan System for Reporting Salivary Gland Cytopathology acknowledges this difficulty, and recommends benign or malignant classification only when definitive diagnostic features of a specific neoplasm are present. For indeterminate cases, the subcategorization of salivary neoplasm of uncertain malignant potential is recommended.

Analysis of the Clinical Relevance of Histological Classification of Benign Epithelial Salivary Gland Tumours

INTRODUCTION

A vast increase in knowledge of numerous aspects of malignant salivary gland tumours has emerged during the last decade and, for several reasons, this has not been the case in benign epithelial salivary gland tumours. We have performed a literature review to investigate whether an accurate histological diagnosis of the 11 different types of benign epithelial salivary gland tumours is correlated to any differences in their clinical behaviour.

METHODS

A search was performed for histological classifications, recurrence rates and risks for malignant transformation, treatment modalities, and prognosis of these tumours. The search was performed primarily through PubMed, Google Scholar, and all versions of WHO classifications since 1972, as well as numerous textbooks on salivary gland tumours/head and neck/pathology/oncology. A large number of archival salivary tumours were also reviewed histologically.

RESULTS

Pleomorphic adenomas carry a considerable risk (5-15%) for malignant transformation but, albeit to a much lesser degree, so do basal cell adenomas and Warthin tumours, while the other eight types virtually never develop into malignancy. Pleomorphic adenoma has a rather high risk for recurrence while recurrence occurs only occasionally in sialadenoma papilliferum, oncocytoma, canalicular adenoma, myoepithelioma and the membranous type of basal cell adenoma. Papillomas, lymphadenoma, sebaceous adenoma, cystadenoma, basal cell adenoma (solid, trabecular and tubular subtypes) very rarely, if ever, recur.

CONCLUSIONS

A correct histopathological diagnosis of these tumours is necessary due to (1) preventing confusion with malignant salivary gland tumours; (2) only one (pleomorphic adenoma) has a considerable risk for malignant transformation, but all four histological types of basal cell adenoma can occasionally develop into malignancy, as does Warthin tumour; (3) sialadenoma papilliferum, oncocytoma, canalicular adenoma, myoepithelioma and Warthin tumour only occasionally recur; while (4) intraductal and inverted papilloma, lymphadenoma, sebaceous adenoma, cystadenoma, basal cell adenoma (apart from the membranous type) virtually never recur. No biomarker was found to be relevant for predicting recurrence or potential malignant development. Guidelines for appropriate treatment strategies are given.