Palisaded encapsulated neuroma (solitary circumscribed neuroma of skin) of the eyelid: report of two cases and review of the literature.

Palisaded encapsulated neuroma of the skin (PEN) is an uncommon benign neural tumour that occurs on the head and neck, including the eyelid, but is unfamiliar to many ophthalmic clinicians. For the first time in the ophthalmic literature, the clinical and histopathological features of two patients with PEN of the eyelid are described. Two cases of PEN were identified in the archives of the Department of Pathology, Institute of Ophthalmology, London. Clinical details were derived by a case note review and the histopathological features defined using standard methods including immunohistochemistry. Two cases of PEN are described, from the eyelids of patients aged 43 and 70 years. The tumours were virtually identical in nature, being painless solid masses composed of a mixture of S100 positive Schwann cells and scattered neurofilament positive nerve fibres. An incomplete thin fibrous capsule, which contains EMA positive perineural cells, partially surrounded each lesion. The lesions were distinguishable from other more common eyelid lesions only on histopathological examination. Both tumours were completely excised with no evidence of recurrence. Neither patient had signs of any associated systemic disease. PENs are usually solitary, firm, non-pigmented, dome-shaped lesions that are found on the face of patients usually over the age of 40 years. Most often these lesions are diagnosed clinically as basal cell carcinomas, dermal naevi, or skin adnexal tumours. Histologically, PENs must be differentiated from other neural tumours that may be associated with systemic syndromes, such as neurofibromas or mucosal neuromas.