Isolated plexiform neurofibroma over left palm: a case report and review of literature.

Plexiform neurofibroma is common over the branches of trigeminal and cervical nerves over the face. Plexiform neurofibroma over palm is rare and affects the individuals with fine motor functions of hand. Here, we report a case of isolated plexiform neurofibroma over the palm with review of literature.

What was known?

1. Plexiform neurofibroma is common over the branches of trigeminal and cervical nerves over the face.

2. Plexiform neurofibroma over palm is rare and affects the individuals with fine motor functions of hand.

Introduction

Neurofibromatosis type 1 (NF 1) (Von Recklinghausen's disease) is a multi-system disease with a frequency of 1 per 2500-3300 births.[1] The inheritance is autosomal dominant with variable penetrance. The gene for NF 1 is located in chromosome 17q 11.2 and encodes for protein neurofibrin.[2] Sporadic cases (new mutations) may occur in 50% of cases.[2] It is characterized by multiple neurofibroma and café-au-lait macules (CALM). CALM are well circumscribed, light-brown macules present in 90% cases of NF 1.[3] Ricacardi[4] has described many clinical types of neurofibromatosis. Other diagnostic features of NF 1 are axillary or inguinal freckling, optic glioma, lisch nodules, sphenoid dysplasia, and NF 1 in a first degree relative.

Case Report

A 19-year-old female presented to skin outpatient department with soft, asymptomatic swelling over middle of left palm of 8 years duration. The onset of the swelling was spontaneous and gradually progressive. As the swelling was asymptomatic, parents neglected the swelling until they started to plan her marriage. There was no past history of trauma or surgery over left palm or similar complaints in family. Examination revealed large 4 × 6 soft skin colored growth over left palm with feel of ‘bag of worms’ on palpation [Figure 1]. CALM were conspicuously absent and there were no other nodules present on the body. The growth was completely excised under local anesthesia and sent for histopathological study. Histopathology of the tumor showed bundles of spindle-shaped cells arranged in whorl pattern in deep dermis, which confirmed the clinical diagnosis of plexiform neurofibroma [Figure 2].

Figure 1

Plexiform neurofibroma - a large skin colored tumor seen over middle of left palm

Figure 2

Plexiform neurofibroma (H and E, ×40) - higher magnification of the tumor showing spindle cells in deep dermis (whorl pattern)

Discussion

NF 1 is an autosomal dominant condition with incidence of 1 in 3000 live births.[5] Type 2 neurofibromatosis has incidence of 1 in 40,000 live births.[1] The NF1 gene is located on the long arm of chromosome 17q11.2, which encodes a 327 kDa protein called neurofibromin.[6] The exact function of neurofibrin is poorly understood.

In 1987, a conference at National Institutes of Health (NIH) had agreed to 7 point diagnostic criteria of patients with NF1. The diagnosis of NF1 is established when two or more of these seven features listed below are present:[7]

Six or more CALM larger than 5 mm in greatest diameter in prepubertal individuals; 15 mm in greatest diameter in postpubertal individuals.

Two or more neurofibromas of any type or one plexiform neurofibroma.

Freckling in the axillary or inguinal regions.

Optic glioma.

Two or more Lisch nodules (iris hamartomas).

A distinctive osseous lesion, such as sphenoid dysplasia or thinning of the long bone cortex, with or without pseudoarthrosis.

A first-degree relative with NF-1 according to the above criteria.

Plexiform neurofibromas are benign peripheral nerve sheath tumors that can be seen in either type of nerufibromatosis. They are diffuse, large, elongated fibromas, histologically similar to discrete neurofibromas and commonly seen on the face and neck and sometimes can lead to massive enlargement of a limb or some other part of body (elephantiasis neuromatosa).[89] Their growth rate is highly variable. Often, overlying hyperpigmentation (“giant café-au-lait spot”) or hypertrichosis can be seen.[10] In this tumor, the nerve is converted into convoluted mass and on palpation feels like “bag of worms”. Isolated cases of plexiform neurofibroma without any association with NF1 have been reported in literature.[11-13]

Plexiform neurofibromas can be of two types, nodular and diffuse. Diffuse type is also known as elephantiasis neurofibromatosa. Plexiform neurofibromas involving the genitourinary tract or the lower limb are rare, with bladder, upper urinary track, and genital involvement reported in decreasing order of frequency.[14]

The management of patients with plexiform neurofibroma is not well defined and is aimed mostly at controlling symptoms. Surgical excision is probably the only therapy available because there is no medication that can prevent or treat plexiform neurofibromas. However, the results of surgical excision can be poor and the procedures can be complicated due to the size, location, vascular status, neural involvement, microscopic extension of the tumor, and the high rate of tumor re-growth.[15]

What is new?

A case of isolated plexiform neurofibroma over the palm is reported here on account of its rarity.