To explore the diagnostic features of clear cell type oxyphilic adenoma of salivary gland in retroauricular lymph nodes.

The clinical and pathological data of a patient with clear cell type oxyphilic adenoma of salivary gland in retroauricular lymph node admitted to the Department of Otorhinolaryngology, the 928th Hospital of the Joint Support Force on January 21, 2022 were retrospectively analyzed, and the diagnostic characteristics were summarized combined with literature.

A 15-year-old female patient presented with a mass behind her left ear 3 years ago, whose size initially was like a " peanut" and subsequently enlarged to the size of a " quail egg". Physical examination found that the neoplasm was under the subcutaneous layer of the left ear, medium in texture, clear in boundary, and average in motion. Color Doppler ultrasound showed a solid mass, about 3.3 cm×2.8 cm in size, with clear boundary and uneven internal echo. There were no abnormalities in the bilateral parotid glands and thyroid glands. Chest and abdominal CT examinations showed no abnormalities. During the operation, it was found that the mass was located in the subcutaneous lymph node group behind the ear, about 0.5 cm away from the left parotid gland. Postoperative pathological examination showed that the tumor size was 4.0 cm×3.2 cm×2.6 cm, with a gray-red and yellow-white surface, irregular oval, complete capsule, a gray-yellow and gray-white section, and soft texture. HE staining showed eosinophilic epithelial cells with dense acinar proliferation, clear cells and foamy cells within the fibrous capsule, with residual lymphoid tissue space at the edge of the capsule. The nuclei of the tumor cells were centrally located, with few nucleoli and rare mitotic figures. The cytoplasm was abundant. Immunohistochemical staining showed positive for broad-spectrum cytokeratin (CK), a small amount of high weight molecular cytokeratin (HCK), and low weight molecular cytokeratin (LCK), while negative for P63, S-100, smooth muscle actin (SMA), Vimentin, renal cell carcinoma (RCC) marker, thyroglobulin (TG), P53, estrogen receptor (ER), progesterone receptor (PR), carcinoembryonic antigen (CEA), discovered on GST-1 protein (Dog-1), human epidermal growth factor receptor 2 (Her-2), carbohydrate antigen 125 (CA125), thyroid transcription factor-1 (TTF-1). The Ki-67 nucleoprotein positive rate was 1%-2%. The pathological diagnosis was a clear cell type oxyphilic adenoma of salivary gland in retroauricular lymph nodes.

The oxyphilic adenoma can occur in the lymph nodes located behind the ear, which may be related to heterotopic salivary glands in lymph nodes. It displays younger age and cell hyaline degeneration when compared to primary oncocytoma in the salivary gland. The clinical signs, histological traits, and immunohistochemical properties of this tumor must be meticulously coupled to make a diagnosis.