Less commonly, kidney lesions, including cysts, polycystic disease, hamartomas, or Wilm's tumors, can be present.(22) Parathyroid carcinoma has also been reported in familial isolated hyperparathyroidism.(17,23) Recently, parathyroid carcinoma, as defined pathologically, has been reported in multiple endocrine neoplasia type 1 (MEN1) syndrome and with somatic MEN1 mutations.(24–26) However, recurrent parathyroid disease in MEN1 may mimic, but not actually be caused by, malignancy. This evidence concerns the gene MEN1 and multiple endocrine neoplasia type 1.