The patient has a bump under the skin of the arm, and there are many clinical conditions that present with a similar symptomatology. The first is that the patient may have a sebaceous cyst, which is also known clinically as a pemphigoid. In other cases, there may be enlarged lymph nodes in the area, or lipomas or dermatofibromas, which may also present a similar symptomatology. Sometimes it may be difficult to distinguish them by appearance alone. It is best for patients to visit the dermatology department of a regular hospital because the doctor can further confirm the diagnosis not only by interview, but also by palpation or some related tests. Generally, these common diseases are not a malignant condition in clinical practice. Most of the cases, such as powdery tumors, fibroids and lipomas, can be solved by surgery.