Sinonasal Tract Neurofibroma: A Clinicopathologic Series of 12 Cases with a Review of the Literature.

Neurofibroma (NF), a benign peripheral nerve sheath tumor, is very uncommon in the sinonasal tract, with only a few reported cases in the English literature. Cases within the files of the authors' institutions confined to the sinonasal tract were compared to cases reported in the English literature (Medline 1966-2014). The 12 patients included 6 females and 6 males, aged 26-75 years (mean 46.2 years). The patients usually presented clinically with a mass lesion (n = 11), obstruction (n = 4) or pain (n = 3), with an average symptom duration of 42.9 months. Two patients had neurofibromatosis (NF1). Tumors involved the nasal cavity alone (n = 8), maxillary sinus alone (n = 2), or mixed sites (n = 2), with a range of 0.4-4.1 cm (mean 2.2 cm). The tumors were circumscribed, composed of spindled to wavy cells with curvilinear nuclei set in a background of collagenized stroma and mast cells. Nuclear palisading and perivascular hyalinization were not seen. Mitoses were scant. Pleomorphism, necrosis and increased cellularity were absent. By immunohistochemistry, the lesional cells were S100 protein, SOX10 and NFP positive, while CD34 highlighted the perineurium. INI1 was intact, with strong nuclear expression in all cases. All patients had surgical excision without recurrence (mean follow-up 8.6 years). The principle differential diagnoses include schwannoma, perineurioma, fibromatosis, and solitary fibrous tumor. NF of the sinonasal tract occurs in middle-aged patients without a gender predilection, usually with non-specific symptoms present for a long duration. Tumors are relatively large (mean 2.2), and usually affect one site only. Surgery is curative, with only 16.7 % NF1 associated. S100 protein, SOX10 and NFP highlight the Schwann cells, with CD34 highlighting the perineural fibroblasts.