Adenocarcinoma is a malignant tumor originating from the salivary gland epithelium, with variable structures but no residual components of pleomorphic adenoma. It accounts for 9% of salivary gland epithelial tumors and is one of the more aggressive types among salivary gland malignancies.

bubble_chart Pathological Changes

(1) Gross Morphology The tumor is round or oval in shape, mostly without a complete capsule. The texture is moderately firm, and the cut surface appears grayish-white.

(2) Microscopic Examination Tumor cells exhibit significant atypia and variable structures. Some are arranged in solid masses or small cord-like patterns, while others show glandular lumen formation or tubular or gland-like structures. Generally, those with glandular lumen-like structures are considered to have a higher degree of differentiation and lower malignancy. The amount of connective tissue between small cords and clusters varies; when abundant, it resembles scirrhous carcinoma, whereas cases with sparse stroma and abundant cancer cells may be termed medullary carcinoma.

(3) Biological Characteristics Adenocarcinoma is highly invasive and exhibits destructive growth patterns. It tends to invade blood vessel and lymphatic walls, leading to a higher incidence of hematogenous and lymphatic metastasis.

bubble_chart Clinical Manifestations

Adenocarcinoma mainly occurs in the parotid gland and minor salivary glands of the palate, and is more common in middle-aged and elderly patients.

Adenocarcinoma grows relatively quickly and has a short disease course. The tumor exhibits invasive growth, often with unclear boundaries from normal tissue, poor mobility, or even fixation. In advanced stages, it may invade the skin, muscles, nerves, and bone tissue, leading to symptoms such as ulcers on the tumor surface, pain, and difficulty opening the mouth. When occurring in the parotid gland, it may adhere and fixate to the external auditory canal, temporal bone, and mandible; when occurring in the submandibular gland, it may fixate to the floor of the mouth and mandible.

Due to the infiltrative growth pattern of adenocarcinoma, extensive wide excision should be performed. The lymph node metastasis rate of adenocarcinoma is relatively high, reaching up to 36-47%, so radical or selective neck dissection should be performed simultaneously with the removal of the primary lesion. Regarding the management of the facial nerve, whether facial nerve paralysis has occurred or not, sacrificing the facial nerve is necessary to ensure complete tumor resection. Intraoperative frozen section pathology should be used to examine the surgical margins for residual tumor cells.

Adenocarcinoma is not sensitive to radiation, so radiation therapy alone is not suitable, but postoperative adjuvant therapy may improve outcomes. For advanced-stage cases where surgery is not feasible, palliative radiotherapy can provide some control, though it cannot achieve curative results. Postoperative adjuvant chemotherapy may also be employed.

bubble_chart Prognosis

Adenocarcinoma has a high rate of lymph node metastasis, is prone to recurrence, and has a poor prognosis. Lin Guochu reported 68 cases of adenocarcinoma, with 5-year and 10-year cure rates of 43.9% and 29.0%, respectively.