Parathyroid adenomas are usually oval in shape. They have greyish brown appearance and may contain foci of hemorrhage (shown here), calcification, or cystic change. Females are more commonly affected; female : male ratio = 3:1; Mean age at presentation is about 40 years. Most lesions are solitary; although rare cases involve more than one parathyroid. Parathyroid adenomas can occur as a component of Multiple Endocrine Neoplasia type 1 syndrome (Wermer Syndrome). MEN 1 gene, a tumor suppressor gene located on chromosome 11q13, is inactivated in MEN 1 syndrome. Sporadic parathyroid tumors have also been found to have MEN 1 mutations (see additional details in next slide).