Adult perithyroid and cervical thymus-parathyroid unit: case reports of a rare entity.

The thymus-parathyroid unit (TPU) occurring in adults is rare.The main symptoms and important clinical findings are as follows: 2 patients presented with neomercazole-resistant Basedow-Graves disease. A third patient presented with thyroid nodules and a fourth patient with a neck mass after thyroid resection for medullary thyroid carcinoma.The main diagnoses were those of thyroid nodules (either in the context of goiter, or not). In the fourth case the diagnosis was of thyroid medullary carcinoma recurrence in the neck. Thyroidectomy was performed in the 2 cases of Basedow-Graves disease and in the third case (wherein selective neck dissection was also performed). In the fourth case, a neck dissection was performed for a possible medullary carcinoma recurrence. A TPU was microscopically detected in 2 cases with perithyroid location, on thyroidectomies for Basedow-Graves disease and in the 2 other cases with neck soft tissue location (associated with thyroid papillary carcinoma and thyroid medullary carcinoma extension). Postsurgical hypocalcemia requiring treatment occurred in both patients with Basedow-Graves disease and in the fourth patient. The presence of TPU should be acknowledged because such lesions can be misdiagnosed as suspect lymph nodes during thyroid surgery for malignant tumors.