My Mother Has Recently Been Suffering With Raised "nodules" Under

My mother has recently been suffering with raised "nodules" under her skin. Locations vary day to day, but they are approx 1" in dm with no discoloration or itching.. just raised and tender. On back, arms, legs. Very strange. She mentioned it to her internist and he ordered her to get an mri stat with contrast. Said he had never heard of anything like what she is experiencing. Possible causes?