Biopsy was undertaken.

MICROSCOPIC DESCRIPTION: The sections show fragments of cellular tumour infiltrating bone, cartilage and sinonasal mucosa. The tumour consists of sheets of moderately discohesive cells with a plasmacytoid appearance, large markedly pleomorphic nuclei with coarse chromatin and prominent nucleoli. There is frequent binucleation and a small amount of cytoplasmic brown pigment. Mitoses including atypical forms are frequent. By immunohistochemistry the tumour cells are Melan-A positive, HMB45 positive (focal), S100 negative, cytokeratin AE-13 negative, CAM 5.2 negative, Cd45 negative.

DIAGNOSIS: 1. Nasal mass, biopsy: Malignant melanoma.