Abstract

Blue nevi are characterized by a dermal proliferation of pigmented dendritic spindled melanocytes with associated pigmented macrophages. They most commonly occur in the skin as blue-grey solitary nodules or plaques, but they can also affect mucosal surfaces like the oral cavity. However, it is extremely rare for blue nevi to arise in the sinonasal cavity. An 88-year-old male presented to the Otolaryngology clinic for bilateral endoscopic sinus surgery for the resection of bilateral mucoceles. During the procedure, a small area of dark discoloration was incidentally discovered on the medial wall of the maxillary sinus. A biopsy of the area was taken, and the histologic sections showed sinonasal mucosa with an underlying proliferation of spindled dendritic melanocytes with surrounding melanophages. Immunohistochemical stains were performed in which the melanocytes stained positive for S-100, HMB-45, SOX-10, and MART-1. These microscopic features rendered the diagnosis of a blue nevus. Increased awareness of this rare entity is pivotal to avoid potential misdiagnosis of a sinonasal malignant melanoma.