Common benign tumors include lipomas, non-viral papillomas, sebaceous gland adenoma, and perianal gland adenomas. Tumours of the small intestine include gastrointestinal stromal tumours, lipomas, hamartomas and carcinoid syndromes. Benign fatty tumors known as lipomas can form on the mesentery. The differential diagnosis include other cardiac tumors such as lipomas and rhabdomyomas (and rarely teratomas). Adenolipomas are lipomas associated with eccrine sweat glands. Pectoralis major muscle in rare occasions may develop intramuscular lipomas. Some superficial lipomas can extend into deep fascia and may complicate excision. Adiposis dolorosa (Dercum disease) is a rare condition involving multiple painful lipomas, swelling, and fatigue. Injection of phosphatidylcholine in lipomas has been studied, though results have been mixed. In some cases, a biopsy of the lipomas may be necessary to confirm the diagnosis. New methods under development are supposed to remove the lipomas without scarring. In dogs, lipomas usually occur in the trunk or upper limbs. Usually, treatment of lipomas is not necessary, unless they become painful or restrict movement. Some patients who are concerned with cosmetics seek removal of individual lipomas. The presence of multiple lipomas, lipomatosis, is more commonly encountered in men.