Ⅰ. INTRODUCTION
Papilloma is a benign tumor commonly found in the oral cavity. It presents as an exophytic, finger-like growth of stratified squamous epithelium. Lesions that histologically show an endophytic or inverted growth pattern are rare, and those that originate in the salivary ducts include intraductal papilloma, inverted ductal papilloma, and sialadenoma papilliferum1-3).
Intraductal papilloma is a relatively rare benign lesion that arises from the ductal system and shows a characteristic papillary growth of ductal epithelium4-6). The lesion presents as a well-defined, painless submucosal nodule. Although cases originating from the major salivary glands have been reported, this lesion most commonly occurs in the minor salivary glands, particularly in the lips and buccal mucosa. 3,5,6).
This report presents a rare case of a 46-year-old female patient who developed intraductal papilloma in the left retromolar trigone.
Ⅱ. CASE REPORT
A 46-year-old woman visited Kyungpook National University Dental Hospital with a chief complaint of an exophytic mass in the left retromolar trigone. The left mandibular third molar was extracted four years ago, and the patient noticed the mass after extraction, but the lesion was not significant at that time. Since then, she had no discomfort or other symptoms. Approximately one year ago, the lesion increased in size when she was in poor physical condition, and touching the lesion caused pain. At her first outpatient visit, a well-defined, oval-shaped nodular lesion was observed in the posterior area of the left mandibular second molar, measuring approximately 2 x 1.5 cm. The central area of the mass appeared bluish in color with a smooth surface (Fig. 1B). On palpation, the mass was slightly tender. The panoramic image did not show any abnormal findings or osteolysis (Fig. 1A). Based on clinical features, hemangioma was considered a provisional diagnosis. Surgical excision was performed under general anesthesia. The mass was carefully excised to preserve anatomical structures (Fig. 1C). The mass was split into two, and the cystic cavities were filled with mucinous material (Fig. 2A). The specimen was sent for histopathological evaluation. On histologic examination, the cystic lumen was lined by cuboidal or columnar epithelium, with numerous arborizing papillary projections extending into the lumen. Based on these findings, the lesion was finally diagnosed as intraductal papilloma (Fig. 2B–D). The postoperative healing was uneventful, and no recurrence of the lesion was observed after 24 months of follow-up (Fig. 1D).
Ⅲ. DISCUSSION
Intraductal papilloma is a rare benign lesion of the salivary duct. The lesion tends to occur in elderly and middle- aged adults but is rare in children. Gender distribution has remained essentially even4,5). Reports in the literature indicate 14 cases in the major salivary glands and 36 cases in the minor salivary glands. Among the major salivary gland lesions, the parotid gland is the most common, and among the minor salivary gland lesions, the lip is the most frequent, followed by the buccal mucosa5,7,8). Additionally, some cases have been reported in the larynx9).
Clinically, intraductal papilloma presents as a solitary, painless, small mass. It is difficult to diagnose based on appearance alone. Radiological imaging such as CT or MRI can aid in diagnosis by confirming the location and extent of the lesion. In addition, ultrasonography or fine-needle aspiration (FNA) can be used. However, it is unclear whether radiologic imaging or FNA is helpful for small lesions10). Histologic diagnosis by surgical excision or removal is essential for diagnosis of the mass. A combination of pathology and immunohistochemistry can lead to an accurate diagnosis and prevent misdiagnosis.
Lesions with histologic features similar to intraductal papilloma include inverted ductal papilloma and sialadenoma papilliferum2,4). They are categorized under the term “ductal papilloma”, and the characteristic microscopic feature is the papillary growth of ductal epithelium11). Sialadenoma papilliferum presents as an exophytic papillary mass with a well-defined sessile base. The exophytic papillomatous component consists of keratotic squamous epithelium, while the underlying component shows a proliferation of ducts forming tortuous clefts, often with papillary projections. The ducts are lined by a double row of basilar cuboidal and luminal columnar cells3,12,13). Inverted ductal papilloma appears as a nodular submucosal mass with a papillary or wrinkled surface. It is thought to arise at the junction of the excretory duct and the surface mucosal epithelium. Histologically, it exhibits an unencapsulated, well-demarcated endophytic epithelial mass14,15). Intraductal papilloma is believed to originate from the salivary gland duct epithelium, most likely the excretory duct. Histologically, it is a unilocular cystic lesion with a single intraluminal papillary projection of neoplastic ductal epithelium. The lumen contains branching papillary elements and fibrovascular cores lined by columnar epithelium. Mucin-containing goblet cells are also present on the papillary surface7,8,15-17).
Intraductal papilloma is generally considered a benign tumor, but recent studies have reported malignant cases exhibiting papillary features 17,18). As this is an uncommon lesion, the causality of malignant transformation has not yet been established. Surgeons should consider this possibility and perform precise and thorough surgical management. Continuous postoperative monitoring and evaluation of the patient's overall condition are essential for improving prognosis and facilitate early detection of potential complications.
