Chapter 46: Neurofibroma

INTRODUCTION

Neurofibromas (NFs) are benign, soft, pink, neuromesenchymal tumors that can be solitary or multiple (Fig. 46.1). Solitary tumors are not associated with systemic findings. Multiple NFs are associated with neurofibromatosis types I and II, both neurocutaneous disorders with important systemic manifestations including malignancies. Plexiform NFs are seen in patients with neurofibromatosis type I.

EPIDEMIOLOGY

Incidence: common

Age: young adults

Race: none

Sex: equal

Precipitating factors: multiple NFs are seen in association with neurofibromatosis I and II. There are no precipitating factors for solitary NFs

PATHOGENESIS

The pathogenesis of solitary lesions is unknown. Multiple germline and somatic mutations have been identified for patients with neurofibromatosis types I and II.

PATHOLOGY

NF is characterized by a well-circumscribed, unencapsulated dermal and subcuticular collection of small nerve fibers and loosely arranged spindle cells possessing wavy nuclei in an eosinophilic matrix. Mast cells are commonly seen. Mitoses are absent.

PHYSICAL LESIONS

NFs present as skin colored to pink to brown soft or rubbery, papules or nodules (Fig. 46.2). The ability to easily invaginate the lesion with pressure, known as “buttonholing,” is a characteristic physical finding. They range in size from a few millimeters to a few centimeters. Plexiform NFs are characterized by large, bag-like masses that may have associated hyperpigmentation.

DIFFERENTIAL DIAGNOSIS

Dermal nevi; congenital nevi; dermatofibromas; neuromas; and fibromas

LABORATORY EXAMINATION

A solitary NF does not merit a workup. Biopsy may be indicated of a clinically atypical NF. Multiple NFs merit referral to neurologic, ophthalmologic, genetics, and orthopedic specialists to assess for neurofibromatosis I or II. Complete skin and eye examination of the patient and immediate relatives is indicated as well. Skin examination should assess for axillary freckling, café au lait macules, plexiform NFs, juvenile xanthogranulomas, and Lisch nodules.

COURSE

They tend to grow indolently and painlessly. Plexiform NF require continuous monitoring for potential malignant change.

KEY CONSULTATIVE QUESTIONS

• Number of lesions

• Family history

• Central nervous system (CNS) abnormalities

• Scoliosis

• Eye abnormalities

• Bone defects

• Loss of hearing

MANAGEMENT

There is no medical indication to treat NFs unless they produce pain or are cosmetically disfiguring or are changing in growth. Many patients, however, request treatment for improvement of cosmetic appearance.

TREATMENT