Palisaded Encapsulated Neuroma in a Zosteriform Distribution.

Sir,

Palisaded encapsulated neuroma (PEN) is a distinctive benign neural tumor, which typically presents as small, solitary, asymptomatic, rubbery, skin-colored or pink papule or nodule. It is nearly always present on the face or on the mucocutaneous junction.[1] Cases of multiple mucosal neuromas have been reported in association with multiple endocrine neoplasia (MEN) 2b syndrome but very rarely, multiple cutaneous palisaded encapsulated neuromas have been found in adult patients without features of MEN2b.[2] Here, we present a rare case of zosteriform cutaneous palisaded encapsulated neuroma on the neck in a patient without neurofibromatosis or MEN 2b.

A 48-year-old female presented with pruritic, multiple, discrete, skin-colored nodules on the neck along the distribution of the cervical spinal nerve (C2, 3) for an unknown period [Figure 1]. The patient had no mucosal lesions, axillary frecking, or café-au-lait macules. Her medical history was unremarkable. There was no accompanying history of hearing defect or other neurological disorders. None of the family members were affected with a similar skin lesion. A biopsy from the lesion revealed encapsulated dermal nodules where the tumor cells had eosinophilic cytoplasm, and wavy, basophilic nuclei with no pleomorphism which are positive for S100 protein [Figure 2]. The clinical and histological findings were consistent with palisaded encapsulated neuroma. After the diagnosis, the patient was sent to the plastic surgery department for complete excision.

Figure 1

There are multiple, zosteriform, discrete, flesh colored, soft to firm, papules and nodules on the neck

Figure 2

Skin biopsy specimen revealed a normal epidermis. In the dermis, there was a partially encapsulated, well-circumscribed nodules composed of fascicles of small spindle cells with wavy nuclei interlaced with small slits and clefts which are positive for S100 protein. There was no nuclear pleiomorphism or mitoses. (H and E, ×500 μm (a), x1000 ìm (b), x100 ìm (c), S100 protein (d))

Palisaded encapsulated neuroma (PEN) of the skin was first described by Reed et al. in 1972.[1] A typical lesion is a solitary, small, asymptomatic, skin colored papule that arises mostly on the face or on the mucocutaneous junctions.[2] It is a rare, benign cutaneous neural tumor, often misdiagnosed as neurofibroma, basal cell carcinoma, melanocytic nevus, epidermal cyst, or skin appendage tumor, and has a histological appearance between that of a neurofibroma and a schwannoma.[13] Differentiation from neurofibromas is essential, because the latter is often associated with neurofibromatosis, and has a propensity for malignant transformation.[4] Histopathologically, the tumor is a well circumscribed nodule situated in the dermis and is composed of a partially encapsulated mass of schwann cells arranged in interlacing fascicles separated by small clefts, interspersed with a variable amount of tiny axons.[5] On the other hand, neurofibromas lack a capsule, contain mucopolysaccharide ground substance, and have fewer axons with myelin sheaths.[5] Schwannomas are located subcutaneously, contain Antoni A and B type tissue with Verocay bodies, and do not have axons.[4]

Our case is rare because presentation with multiple palisaded encapsulated neuroma is not well documented and pattern of the distribution is zosteriform. To the best of our knowledge, there have been nine reported cases of multiple lesions.[5] Most of cases showed wide distribution or linearly arranged. Only one case was similar zosteriform presentation arranged on the face along the distribution of the ophthalmic division of the trigeminal nerve.[4] Some of these occurred in patients with features of MEN while others occurred in the absence of other syndromic features.[5] Treatment of solitary or multiple lesion is excision. It is curative with a minimum possibility of recurrence.[4]

Awareness of the multiple variant is important and by itself should not preclude a diagnosis of palisaded encapsulated neuroma.