What is your diagnosis? Submandibular mass in a dog

Abstract

A 14-year-old Chow Chow presented to NC State University Veterinary Hospital for evaluation of a right submandibular mass, present for approximately 3 months. The mass was initially noted due to the regional matting of hair, but the patient had also developed stertor and coughing. Physical examination revealed a firm 2.1 × 2.4 × 3.3 cm mass in the area of the right submandibular salivary gland.Ultrasound of the right mandibular salivary gland revealed multiple heterogeneous to hypoechoic nodules with fluid-filled cavitations. A computed tomography (CT) scan confirmed a mass surrounded by small peripheral vessels and a small amount of normal appearing salivary tissue. There were also small, mineral attenuating foci in the right parotid salivary gland as well as a left parotid duct sialodocholith. The left mandibular salivary gland and regional lymph nodes were normal. No overt evidence of metastatic disease was seen on thoracic radiographs or CT imaging.Four milliliters of cloudy straw-colored fluid, along with several aspirates of solid tissue, were acquired from the mass using ultrasound guidance, and samples were submitted for cytologic examination (Figure 1A, B). Three needle biopsies were also obtained for histopathology. A BF I G U R E 1 Photomicrographs of (A) a fine-needle aspirate from a salivary gland mass and (B) a cytocentrifuged preparation of fluid from the mass in a Chow Chow dog. Modified Wright-Giemsa stain, ×100 objectiveThe tissue aspirate revealed many variably cohesive basophilic clusters of epithelial cells on an amphophilic background with amorphous basophilic mucoid material ( Figure 1A). Loosely cohesive clusters had indistinct cytoplasmic borders and many stripped nuclei embedded in a background of cytoplasm. Most of the cells exhibited mild anisocytosis and anisokaryosis and were characterized by ovoid nuclei, occasional single to multiple prominent nucleoli, and small amounts of basophilic cytoplasm. Occasional large cells with large nuclei and increased nuclear:cytoplasmic ratios were noted. Rare aggregates of more typical salivary cells were seen with small round nuclei and abundant foamy cytoplasm, and few scattered small lymphocytes, plasma cells, and macrophages were noted.Direct and cytocentrifuged preparations of the fluid were moderately cellular on a pale eosinophilic background with protein crescents and cholesterol crystals, with few aggregates of amorphous eosinophilic mucoid material ( Figure 1B). Cells consisted primarily of nondegenerate neutrophils, macrophages, and lymphocytes with rare salivary epithelial cells both individualized and in clusters. In the background, and occasionally in macrophages, were numerous,