Clinicopathological features of peripheral nerve sheath tumors involving the eye and ocular adnexa.

Peripheral nerve sheath tumors (PNSTs) are known to occur in the orbit and comprise 4% of all orbital tumors, but have not been well studied in contemporary literature. Ninety specimens involving the eye and ocular adnexa (1979-2015) from 67 patients were studied. The mean age was 32.5years. Locations included orbit (58.9%), eyelid (60.0%), and other ocular adnexa. Most specimens were neurofibromas (70.0%), followed by schwannomas (11.1%), neuromas (11.1%), granular cell tumors (n=4), nerve sheath myxomas (n=2), and malignant PNST (n=1). Fifty-six (88.9%) neurofibroma cases were neurofibromatosis 1 associated. Among neurofibromas, 31.7% were localized, 38.1% were plexiform, 25.4% were diffuse, and 4.8% were diffuse and plexiform. These tumors involved skin (31.7%), soft tissue (11.1%), skeletal muscle (22.2%), peripheral nerve (63.0%), lacrimal gland (20.6%), and choroid (n=1). Other histologic findings included pseudo-Meissner corpuscles (27%), Schwann cell nodules (4.8%), prominent myxoid component (7.9%), melanin-like pigment (3.2%), and inflammation (14.3%). Available immunostains included S100 (+ in 15/15 cases), EMA (+ in 2/4 cases), CD34 (+ in 4/4 cases), and Ki-67 (<1% in 4/4 cases). Among 10 schwannomas, 8 were conventional and 2 were plexiform. Observed features included capsule (n=5), hyalinized vessels (n=5), Verocay bodies (n=7), and Antoni B pattern (n=5). Immunostaining included S100+ in 4 of 4 cases, and collagen IV+ and Ki-67 <1% in 3 of 3 cases. Neurofibromas are the most common PNST involving the eye and ocular adnexa, and the majority are associated with neurofibromatosis 1. Plexiform and diffuse patterns and the presence of pseudo-Meissner corpuscles are relatively frequent in this area.