Malignant neoplasms of the paranasal sinuses involving the skin.

Malignant neoplasms of the mucosa and minor salivary glands of the paranasal sinuses may involve the skin by direct extension. When a tumor appears on the overlying skin, these sinuses should be considered as a possible site of origin. Adenoid cystic carcinoma of the paranasal sinuses arise from minor salivary glands. They can infiltrate overlying skin and easily be confused with a primary cutaneous adenoid cystic carcinoma. Malignant melanomas of the paranasal sinuses are clinically very aggressive. They are often amelanotic, and this may lead to an incorrect histopathologic diagnosis. Hence, physical and radiological examination of the nose, mouth, and paranasal sinuses should be performed whenever a tumor appears in the overlying skin that does not have a clear cutaneous origin or whenever the primary site of a metastatic malignant melanoma is unknown.