Adenoid cystic carcinoma of the palate with isolated cutaneous metastasis: a unique case and review of current and future treatment modalities of metastatic disease.

Adenoid cystic carcinoma (ACC) is an aggressive salivary gland neoplasm characterized by high rates of local recurrence, early metastasis, and a poor long-term prognosis. Approximately 20-50% of cases result in distant metastasis, commonly involving the lung, bone, liver, and brain. Cutaneous metastasis is a rare occurrence, with a small number of cases reported previously in the context of multiple metastatic sites of involvement. We present a unique case of ACC of the hard palate with isolated cutaneous metastasis. A 36-year-old woman underwent a subtotal maxillectomy and skull base resection for the treatment of a T4N0 ACC of the right maxilla. One year postoperatively, the patient presented with multiple rapidly growing painful nodules on the skin of the scalp, neck, and chest. Biopsy confirmed metastatic poorly differentiated ACC, and positron emission tomography demonstrated cutaneous metastatic lesions without evidence of other tissue involvement. This case highlights the possible rare and aggressive pathways of metastasis of ACC. Currently there is no consensus for the treatment of disseminated disease, due to the poor efficacy of current treatment modalities. Where isolated metastasis is present, surgical resection can be attempted to control disease progression; however the benefit of metastasectomy on survival is not substantiated. As such, the role of newer targeted systemic therapies needs to be further investigated in the hope of achieving disease control.