Rare tumor of salivary glands

Rare tumors of the salivary glands (Orphanet code 276142) encompass a heterogeneous group of uncommon neoplasms arising from the major salivary glands (parotid, submandibular, and sublingual) or the minor salivary glands distributed throughout the oral cavity, pharynx, and upper aerodigestive tract. These tumors can be benign or malignant and include a wide spectrum of histological subtypes such as acinic cell carcinoma, adenoid cystic carcinoma, mucoepidermoid carcinoma, epithelial-myoepithelial carcinoma, polymorphous adenocarcinoma, salivary duct carcinoma, secretory carcinoma, and other exceptionally rare entities. Because of their diversity, clinical presentation varies but commonly includes a painless or slowly growing mass in the affected gland region, facial nerve dysfunction (particularly with parotid tumors), pain, numbness, or difficulty swallowing depending on tumor location and size. Salivary gland tumors collectively account for approximately 3–6% of all head and neck neoplasms, but individual rare subtypes are exceedingly uncommon. The parotid gland is the most frequently involved site, followed by the submandibular and minor salivary glands. Malignant salivary gland tumors may metastasize to regional lymph nodes, lungs, bone, or liver. Diagnosis typically requires imaging (ultrasound, CT, or MRI), fine-needle aspiration cytology, and definitive histopathological examination of surgical specimens, often supplemented by immunohistochemistry and molecular testing to identify subtype-specific genetic alterations (e.g., MYB-NFIB fusion in adenoid cystic carcinoma, ETV6-NTRK3 fusion in secretory carcinoma). Treatment depends on the specific tumor type, stage, and location. Surgical resection remains the cornerstone of therapy for most salivary gland tumors, with adjuvant radiation therapy recommended for high-grade or advanced-stage malignancies. Chemotherapy has a limited role but may be considered in recurrent or metastatic disease. Emerging targeted therapies, including TRK inhibitors for NTRK fusion-positive tumors and androgen receptor-directed therapy for salivary duct carcinoma, represent promising advances. Given the rarity and complexity of these tumors, management at specialized centers with multidisciplinary head and neck oncology teams is strongly recommended. Prognosis varies widely depending on histological subtype, grade, and stage at diagnosis.

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