Diffuse cutaneous neurofibroma

Diffuse cutaneous neurofibromas are a rare neurofibroma variant, similar to plexiform neurofibromas which may be co-existent. Both neurofibromas and plexiform neurofibromas are discussed separately.

Terminology

There are variable uses and some confusion about the distinction between plexiform neurofibroma and diffuse cutaneous neurofibroma, with some sources not clearly distinguishing between the two. Generally, plexiform neurofibromas are deeper lesions affecting nerves and plexus. The two may, however, co-exist .

Importantly it appears that diffuse cutaneous neurofibromas may not be as closely associated with neurofibromatosis type 1, nor have the same risk of malignant transformation . The distinction is thus important.

Epidemiology

Diffuse neurofibromas mainly affect children and young adults .

Unlike plexiform neurofibromas, diffuse cutaneous neurofibromas are not strongly associated with neurofibromatosis type 1 (NF1), with only 10% of affected individuals having the condition .

Clinical presentation

These tumors most frequently present with overgrowth of the subcutaneous tissues typically of the head and neck, trunk, and extremities.

Pathology

Diffuse cutaneous neurofibromatosis causes plaque-like elevation of the skin with thickening of the entire subcutis but without nodular masses .

Radiographic features

MRI

Diffuse cutaneous neurofibromas usually have fairly non-specific signal intensity :

• T1: iso- to hypointense to skeletal muscle
• T1 C+: usually vivid contrast enhancement
• T2: hyperintense to skeletal muscle

Treatment and prognosis

Again, unlike plexiform neurofibromas, malignant transformation is uncommon .