Lipomatosis of the parotid salivary gland: 2 case reports and review of the literature on fat-containing salivary gland lesions

Two cases of lipomatosis of the parotid salivary gland in two dogs are reported. Both dogs were presented with a slow growing unilateral non-painful mass in the parotid region. The mass measured 12 and 15 cm on the longest axis for case 1 and 2 respectively. Initial incisional biopsies were suggestive of infiltrative lipoma or salivary gland adenocarcinoma. Case 2 underwent head radiographs that showed a soft tissue opacity on the area of the right parotid gland followed by a computed tomography that showed a multi-lobulated infiltrative mass occupying the right parotid gland. Both cases underwent total parotidectomy with an excisional biopsy intent. Surgery on case 1 included total ear canal ablation (TECA). Histology revealed lipomatosis of the parotid gland with a similar admixture of adipocytes and well-differentiated salivary acini on both cases. No recurrence was reported by 4 years for case 1 and by 3 years for case 2. Case 1 developed long-term right-sided facial paralysis and palpebral reflex deficit due to damage of the facial and trigeminal nerve during surgery. The cases are described and the veterinary literature is reviewed in view of the most updated information available in human medicine on fat-containing salivary gland lesions. Considering this literature review, authors recommended these two cases to be classified as lipomatosis of the salivary gland. In conclusion, fat-containing salivary gland lesions should be considered in the list of differential diagnoses in dogs with an enlarged salivary gland and seem to be associated with an excellent prognosis after surgical excision.