Subcutaneous neurofibromas are benign growths that develop beneath the skin’s surface. These tumors originate from nerve sheaths, the protective coverings around nerves. Unlike more superficial skin growths, subcutaneous neurofibromas are often felt rather than immediately seen.
What Are Subcutaneous Neurofibromas?
Subcutaneous neurofibromas grow in the fatty and connective tissue layers just below the dermis. They frequently develop along peripheral nerves. When felt, these tumors typically present as firm, rubbery, or lumpy masses under the skin. While not always visible, some can cause a noticeable bulge or slight discoloration of the overlying skin.
Their size varies considerably, from small, pea-sized nodules to larger masses several centimeters in diameter. Individuals might experience tenderness or pain when pressure is applied, particularly if they impinge on a nerve. Depending on the nerve involved, symptoms can extend to numbness, tingling, or localized weakness. Subcutaneous forms are firmer and deeper than cutaneous neurofibromas, which appear directly on the skin’s surface.
The Link to Neurofibromatosis Type 1
Subcutaneous neurofibromas are a characteristic feature often associated with Neurofibromatosis Type 1 (NF1), a common genetic disorder affecting approximately 1 in 3,000 births worldwide. NF1 is a multi-system condition impacting the skin, nervous system, and bones. While not every individual with a subcutaneous neurofibroma has NF1, multiple such tumors often strongly indicate the disorder.
NF1 is caused by a mutation in the NF1 gene. This gene provides instructions for producing neurofibromin, a protein that acts as a tumor suppressor, regulating cell growth and division. A mutation can lead to dysfunctional neurofibromin, resulting in uncontrolled cell proliferation and tumor formation.
Individuals with NF1 often exhibit other manifestations. These include café-au-lait spots (light brown patches on the skin) and freckling in the armpits or groin. Another common sign is Lisch nodules, benign growths on the iris of the eye. Understanding this connection between subcutaneous neurofibromas and NF1 is important for accurate diagnosis, monitoring, and genetic counseling.
Identifying and Addressing Subcutaneous Neurofibromas
Identification primarily relies on a thorough clinical examination and patient medical history. During a physical examination, a healthcare provider can often palpate these growths. If there are symptoms or concerns, imaging techniques like MRI or ultrasound may be used. These studies provide detailed information about the tumor’s size, depth, and whether it involves or compresses nearby nerves or structures.
Many subcutaneous neurofibromas are benign and do not necessitate immediate treatment, especially if asymptomatic. Regular observation is often recommended, monitoring for changes in size, pain, or new functional impairments. For tumors causing pain or discomfort, initial management may involve over-the-counter pain relievers or localized nerve blocks.
Surgical removal is considered under several circumstances. This includes when the tumor causes significant pain or persistent discomfort. Surgery is also indicated if the tumor compresses nerves or other tissues, leading to functional impairment like muscle weakness or persistent numbness. Cosmetic concerns can also be a reason for removal.
While rare, there is a slight risk of malignant transformation into a malignant peripheral nerve sheath tumor (MPNST). Therefore, any rapid growth, new or escalating pain, or changes in texture warrant immediate medical evaluation.