A neurofibroma is a benign nerve-sheath tumor in the peripheral nervous system. In 90% of cases, they are found as stand-alone tumors (solitary neurofibroma, solitary nerve sheath tumor or sporadic neurofibroma), while the remainder are found in persons with neurofibromatosis type I (NF1), an autosomal-dominant genetically inherited disease. They can result in a range of symptoms from physical disfiguration and pain to cognitive disability. Neurofibromas arise from nonmyelinating-type Schwann cells that exhibit biallelic inactivation of the NF1 gene that codes for the protein neurofibromin. This protein is responsible for regulating the RAS-mediated cell growth signaling pathway. In contrast to schwannomas, another type of tumor arising from Schwann cells, neurofibromas incorporate many additional types of cells and structural elements in addition to Schwann cells, making it difficult to identify and understand all the mechanisms through which they originate and develop. Types
Neurofibromas have been subdivided into two broad categories: dermal and plexiform. Dermal neurofibromas are associated with a single peripheral nerve, while plexiform neurofibromas are associated with multiple nerve bundles. According to the World Health Organization classification system, dermal and plexiform neurofibromas are grade I tumors. Plexiform neurofibroma are more difficult to treat and can transform into malignant tumors. Dermal neurofibroma do not become malignant. Dermal neurofibroma
Anatomy
Dermal neurofibromas (sometimes referred to as cutaneous neurofibromas) originate in nerves in the skin. Three kinds are distinguished:
Discrete cutaneous neurofibromas: Sessile or pedunculated masses on the skin, which are fleshy and non-tender, and can vary in size.
Angiokeratoma is a benign cutaneous lesion of capillaries, resulting in small marks of red to blue color and characterized by hyperkeratosis. Angiokeratoma corporis diffusum refers to Fabrys disease, but this is usually considered a distinct condition. Signs and symptoms
Presentation includes telangiectasia, acanthosis, and hyperkeratosis.Presentation can be solitary or systemic.Multiple angiokeratomas, especially on the trunk in young people, are typical for Fabry disease, genetic disorder connected with systemic complications. Complications
In some instances nodular angiokeratomas can produce necrotic tissue and valleys that can harbor fungal, bacterial and viral infections. Infections can include staphylococcus. If the lesion becomes painful, begins draining fluids or pus, or begins to smell, consult a physician. In these instance a doctor may recommend excision and grafting. Pathophysiology
Histology
Angiokeratomas characteristically have large dilated blood vessels in the superficial dermis and hyperkeratosis (overlying the dilated vessels). Diagnosis
Due to the rarity of different types of vascular conditions, angiokeratomas may be misdiagnosed. A biopsy of the lesion can produce a more accurate diagnosis. Classification
Angiokeratoma may be classified as:

Angiokeratoma of Mibelli (also known as "Mibellis angiokeratoma," "Telangiectatic warts") consists of 1- to 5-mm red vascular papules, the surfaces of which become hyperkeratotic in the course of time. : 589  The disease is named after Italian dermatologist Vittorio Mibelli (1860-1910). Angiokeratoma of Fordyce (also known as "Angiokeratoma of the scrotum and vulva," though not to be confused with Fordyces spots) is a skin condition characterized by red to blue papules on the scrotum or vulva. Solitary angiokeratoma is a small, bluish-black, warty papule that occurs predominantly on the lower extremities.