<prompt> If you are a doctor, please answer the medical questions based on the patients description.My 13 yo son has a lump about 6 inches from his wrist on the underneath of his forearm. I just noticed it today, but he tells me its been there for over a year. He also said it has gotten bigger. It feels like a solid bump, but moves around within a small space. It has a very, very, VERY slight reddish appearance. His yearly checkup is next week. I am just worried that I should get it looked at now. Can you give me an idea if I should go now or wait; i.e. should I worry?  <response>: Hi! Thanks for writing to us sharing your sons problem of the enlarging solid slightly mobile lump on the forearm! If I were your primary physician and had you presented him to me with this problem, I would like to consider following possibilities, as per my experience of ultrasound, CT scan and needle biopsies:1. Benign cyst or cyst-like conditions like bursa, sebaceous cyst, ganglion, hematoma or lymphangioma2. Benign skin nodules or tumors like lipoma, neurofibroma, dermatofibroma, fibrous histiocytoma or other adnexal tumor etc. Therefore, it is benign; you need not worry about this one, but please mention it during his routine testsclinical examination a clinical examination and if needed simple needle biopsy for confirmation of the lesions nature! 