Adenocarcinoma is also known as serous cell adenocarcinoma, which was not considered a type of salivary gland tumor until the 1950s, when it was first described and named systematically by Foote and Frazell in 1953. The tumor was named by the WHO as adenoblastoma because of its malignant nature, but the clinical presentation is often recurrent and metastatic. It is now mostly considered to be a low-grade malignant tumor. The cell morphology of the tumor is completely similar to that of the plasma cells of the glandular follicles, so it is believed that adenoidal cell carcinoma occurs in the glandular follicle cells. However, intercalated duct cells are seen in the lesion and there is a transition from intercalated duct cells to alveolar cells, so it is thought that adenoidal cell carcinoma originates from intercalated duct epithelium. Diagnosis Since there is no characteristic clinical manifestation, it is difficult to make a correct diagnosis before surgery, although special examinations such as salivary gland imaging, CT, B-type ultrasound and radioisotope scan are performed, and the diagnosis is usually confirmed after pathological examination. Treatment measures are mainly surgical resection. Because of the thin envelope and often incomplete, and even small tumor growth outside the envelope, extensive resection should be performed, and subtotal resection including the edge of normal parotid tissue, or total parotidectomy with preservation of facial nerve is more suitable. Whether to perform cervical lymph node dissection should be determined according to the clinical and histological type, and selective cervical lymph node dissection is usually required. Postoperative treatment is usually not required, except for radiation therapy when the lesion is extensive and there is suspicion of residual disease. Because of the possibility of distant metastasis, chemotherapy has been advocated. Pathological changes 1. General morphology: The tumor is usually solitary, with envelope, but incomplete, mostly with clear boundaries with surrounding tissues. It is nodular or lobulated with hard texture. The cut surface is solid and slightly convex, gray-white with brownish-red spots, more brittle, without the moist and mucus-like manifestations of benign mixed tumors. Occasionally, cystic changes are seen, and the capsule contains brownish-red liquid. 2. Microscopic examination: the tumor has a thin perithelium, but infiltration of tumor cells is common within the perithelium. The tumor cells are arranged into solid masses, constituting many similar to normal glandular vesicles, trabeculae, tubules and follicles, but without ducts and duct-like structures. Lobular or lamellar structures are also seen, with a small amount of interstitium with blood vessels and lymphatic-like tissue. Sometimes solid or papillary cystic follicles can be seen within the tumor. The tumor cells are round or polygonal in shape, with small nuclei, deviated nucleoli, and inconspicuous nucleoli. In some cases, the cytoplasm is transparent, and there may be clear cytoplasmic cells and vacuolated cells, which should be distinguished from papillary cystadenoma, metastatic renal clear cell carcinoma and mucinous epidermis-like carcinoma. 3. Biological characteristics: Adenoid cell carcinoma grows slowly and has a long course, but is locally infiltrative and may have recurrence and metastasis. Although the consistency and high differentiation of tumor cells cannot be determined as benign, they should be regarded as low grade malignant. Clinical manifestations Adenoid cell carcinoma is a relatively rare salivary gland tumor, accounting for 1% to 3% of salivary gland tumors, 1% to 4% of macrosalivary gland tumors, and 5.1% to 12% of salivary gland malignancies. According to Garder’s report, it accounts for 7%-15% of the malignant tumors of the major salivary glands. The parotid gland is the most frequent site of occurrence and is almost unique to the parotid gland. However, it has been reported in submandibular gland, sublingual gland and small salivary gland. This tumor can develop from adolescence to old age, but it is most common between 40 and 60 years old, and more common in women than men. Glandular follicular cell carcinoma is clinically similar to mixed tumors and is often a painless mass with occasional symptoms of pain and facial nerve involvement. The disease duration is long, ranging from a few months to several decades. The tumors are mostly round, substantial, may be nodular, moderately textured or slightly hard, and a few have cystic changes, are mobile, and do not adhere to the skin. Late stage may metastasize, with cervical lymph node metastasis being the most common. Prognosis The postoperative recurrence rate of adenoid cell carcinoma is 20% to 55%, the lymph node metastasis rate is 3% to 11%, and the distant metastasis rate is 10% to 12%. Although there is a tendency of metastasis and local infiltration, the malignant degree of adenoid cell carcinoma is low among salivary gland tumors, and the prognosis is generally good. 5-year cure rate is above 88%. The recurrence rate was 33%. In China, Zhang Xiaoshan et al. reported that the 5-year, 10-year and 15-year survival rates were 95.83%, 83.35% and 60%, respectively, and the recurrence rate was 37.14%. The causes of tumor recurrence are multiple, and the local recurrence rate of conservative tumor resection and enucleation is 66.7%, among which 22.2% of patients died from tumor recurrence. For total parotidectomy, the local recurrence rate is 9.5%. Complications The recurrence rate of postoperative alveolar cell carcinoma was 20% to 55%, and the lymph node metastasis rate was 3% to 11%, and the distant metastasis rate was 10% to 12%. The causes of tumor recurrence are multiple, and the local recurrence rate of conservative tumor resection and enucleation patients was 66.7%, of which 22.2% died of tumor recurrence.