Background: The differential for soft tissue tumors of the hand and upper limb is broad. Hematologic malignancy remains quite low on the differential for soft tissue tumors involving the hand, and there is little in the literature describing surgical management of such cutaneous manifestations. When the tumor is large or involves the thumb, careful consideration of reconstructive options is required. Methods: We present a rare case of an aggressively enlarging mycosis fungoides, a cutaneous T-cell lymphoma tumor, involving the thumb. This tumor had a history of multiple failed treatment attempts, including radiation and chemotherapy. Results: Our surgical plan was a reverse radial forearm osteocutaneous flap. Conclusion: A reverse radial osteocutaneous forearm flap was successfully used to avoid thumb amputation and preserve thumb function.