AbstractFrom a review of the world literature, 91 cases of parathyroid cysts have been identified. The majority present as asymptomatic lumps in the lower part of the neck to the right or, more frequently, the left of the midline and are diagnosed as thyroid nodules before surgery. The 4 cases discussed in this article were all derived from the left lower parathyroid gland or left upper pole of the thymus. Three are the largest on record, 2 of which produced pressure symptoms and one, scabbarding of the trachea.