ABSTRACT
The atypical parathyroid adenoma is a histological diagnosis. It is a parathyroid tumor with atypical histological features different from an adenoma and not similar enough to be considered as a carcinoma. It has an uncertain malignant potential. We report the case of a 55-year-old woman, diagnosed with severe hypercalcemia during her follow-up with the rheumatologist for osteoporosis. The laboratory testing led to the detection of a very important level of parathormone PTH 1325.62 pg/ml (20 fold the normal level), confirming the diagnosis of primary hyperparathyroidism. Investigations of the potential causes led to the presence of a large left inferior parathyroid adenoma. The patient was operated and on the examination of the removed tissue, the histopathological examination concluded to an atypical parathyroid adenoma, and the post-operatory PTH level dropped significantly to 152 pg/ml. The atypical parathyroid adenoma is a very rare tumor, and the diagnosis is still a challenge, the outcome of patients is not well known yet, there for the surveillance is important and must be regularly.