Mucinous adenocarcinoma of minor salivary glands: a high-grade malignancy prone to lymph node metastasis

Salivary gland mucinous adenocarcinoma (MAC) is a rarely encountered and poorly understood tumor. We describe two additional cases presenting as a lip lesion of older women. The prognosis was dismal with one death and one patient with recurrent/metastatic disease. Combining these with 19 cases in the literature unveiled that intraoral MAC occurred primarily in the palate (43%) of elderly individuals (average 65 years) with slight male preponderance (59%). Tumor evolved slowly (>2 years) and most (60%) were diagnosed at an advanced stage. Local recurrences were common (33%) and cervical lymph node and distant metastases were frequent (63% and 29%, respectively). About half the patients (47%) died of tumor within 6 years. Both histologically and immunohistochemically, MAC lacked acinar, myoepithelial, and neuroendocrine phenotypes. Cytokeratins 7 and 20 and estrogen and progesterone receptors, in some combination, may assist to distinguish primary versus metastatic mucinous carcinoma. Minor salivary gland MAC belongs to a high-grade category with a significant risk of local recurrence, lymph node metastasis, and fatal outcome.