Doctors can only verify if a skin rash is lymphoma by completing a biopsy of the affected area, notes the American Cancer Society. Doctors may conduct punch, incisional or excisional biopsies of the skin to confirm a lymphoma diagnosis.
Before doing biopsies to confirm if a skin rash is lymphoma, doctors collect medical histories from patients, states the American Cancer Society. Changes in the size and appearance of skin abnormalities, itchiness and pain, and other symptoms like weight loss and fever may be signs that a rash is lymphoma. Doctors may also check the lymph nodes under the skin, as lymphoma can cause lymph nodes to become enlarged. To rule out other causes of skin rashes, doctors also ask patients about exposure to chemicals and other substances that cause rashes.
Doctors who suspect lymphoma remove a piece of skin through a biopsy in order to conduct tests and study the skin under a microscope, notes the American Cancer Society. During a punch biopsy, doctors apply a local anesthetic, then punch out a small piece of skin using an instrument that can punch through all the layers of the skin. Doctors conduct incisional biopsies by removing a piece of the affected area of the skin with a scalpel, or remove the entire area of affected skin in an excisional biopsy. Some patients undergo several biopsies before doctors can confirm that a skin rash is lymphoma.