Parathyroid gland adenoma. Light micrograph of a section through a human parathyroid gland adenoma. Adenomas are benign (non-cancerous) tumours (neoplasms). There are two pairs of parathyroid glands situated behind the thyroid gland in the neck, which control the calcium level in blood. The adenoma cells (pink, oxyphil) have large, irregular, nuclei (purple dots). The adenoma may result in hyper-parathyroidism, which requires surgical removal of the gland (parathyroidectomy), followed by blood calcium level regulating drugs. Magnification unknown.