<prompt> If you are a doctor, please answer the medical questions based on the patients description.my dad just went through 8 hours of chemo and the collection part of the stem cell transplant. he has a port in his chest for the rest of the treatment. just found a lump on his arm, not too big but definitely not small. any idea of what it can be caused from? should we take him to the ER?  <response>: Hi! Thanks for writing to us! You did not mention your fathers primary disease for which the chemotherapy was given; but as stem cell transplantation is involved, I would consider it as a case of leukemia or multiple myeloma. Therefore, a lump on the arm following chemotherapy in a patient with central venous line would be due to:1. A hematoma possibility 202. An abscess possibility 103. Tumor or cancerous nodule possibility 104. Thrombosed vein possibility 105. Benign lump not related to the disease or treatment possibility 50So please get it to the treating doctors notice for a look and tests if necessary for confirmation; 