Mandibular salivary gland plasma cell tumor in a dog

•Salivary gland plasma cell tumors (PCT) are extremely rare in dogs.•A canine mandibular salivary gland extramedullary PCT is described.•MUM1 immunohistochemistry is sensitive and specific in identifying canine PCT.•Prolonged survival and excellent quality of life was afforded by surgical excision. An 8-year-old, intact male, Jack Russell Terrier dog was admitted with a 10-day history of an enlargement in the right submandibular area. Clinical examination revealed a subcutaneous, solid, firmly attached and painless mass (3 × 2 cm) located in the area of the right mandibular salivary gland, in an otherwise seemingly healthy dog. Fine-needle-aspiration cytology suggested a round cell neoplasia, most consistent with a plasma cell tumor. Histopathologic and immunohistochemical (MUM1) examination, following surgical excision of the mass, confirmed the diagnosis of a plasma cell tumor embedded in the right mandibular salivary gland. Clinical staging reasonably excluded a disseminated plasma cell tumor. The dog remains healthy and in complete remission 23 months following surgical excision of the mass. Albeit rare, extramedullary plasma cell tumors can affect the salivary glands of dogs.