Case #41 Discussion

Summary: This adolescent patient complains of a soft tissue enlargement in the area of the right parotid gland.  The lesion is persistent, progressive, well-circumscribed, firm, nontender, and approximately 2 x 4 cm in diameter.  The lesion is a subepidermal soft tissue enlargement that is fixed to underlying structures but not to the epidermis.  The patient is unsure of the duration of the lesion, which may indicate that the lesion has been growing slowly and progressively and has not previously concerned the patient.  Clear saliva can be expressed from all the major salivary gland ducts.  Lesions to Exclude from the Differential Diagnosis: The lesion is described as a soft tissue enlargement.  Reactive soft tissue enlargements can be excluded because the lesion in this case is persistant, progressive, nontender, and localized. Within the category of tumors, high-grade malignant tumors are excluded because the lesion in this case is localized, has a slow growth rate and is nontender.  Squamous cell carcinoma and basal cell carcinoma  can be excluded because the lesion in this case has normal epidermis, indicating that the lesion is arising in tissue beneath the surface epidermis.  Soft tissue cysts may be excluded because they are fluctuant.   Within the category of benign tumors, epithelial tumors are eliminated because the lesion in this case has a normal surface.  From the category of mesenchymal tumors, the following can be excluded. Epulis fissuratum, peripheral ossifying fibroma, peripheral giant cell granuloma and congenital epulis can be excluded based on location.  Hemangioma, lymphangioma, and congenital epulis can be excluded because these present during infancy.  Pyogenic granuloma can be excluded because these lesions are rapidly growing, compressible and vascular in appearance.  Lipoma can be excluded because they are compressible.  Neuroma can be excluded because these have a history of trauma and are painful to palpation.  Lesions to Include in the Differential Diagnosis:  Even though the lesion is fixed to the underlying structures, benign and low-grade malignant salivary gland tumors and some benign mesenchymal tumors are included in the differential diagnosis.  Benign tumors originating in major salivary glands, such as the parotid gland in this case, can be fixed to surrounding structures when they grow to a large size.  The differential diagnosis includes pleomorphic adenoma, monomorphic adenoma, papillary cystadenoma lymphomatosum (although usually present in older patients) and low-grade adenoid cystic carcinoma and acinic cell carcinoma.  Irritation fibroma, leiomyoma, rhabdomyoma, schwannoma and neurofibroma are included in the differential diagnosis, although they would be less likely than salivary gland tumors.  Initial Management and Final Diagnosis: An incisional biopsy was performed, and the lesion was microscopically diagnosed as pleomorphic adenoma (mixed tumor). Management:  A complete excision of the lesion, sometimes with a rim of surrounding salivary gland tissue, would provide a good prognosis.