Sudan IV stain. Its limitations in evaluating parathyroid functional status.

The differentiation of normal, hyperplastic, and adenomatous parathyroid tissue is one of the most important and difficult frozen-section diagnoses a pathologist is called on to make. Recent reports have suggested that the use of neutral lipid stains (Sudan IV or oil red O) for fat droplets within parathyroid chief cells may be useful in separating normal from hyperfunctioning glands. In a combined autopsy and surgical study, we evaluated Sudan IV staining in 73 persons with normal parathyroid glands and 13 patients with hyperfunctioning glands. Although the stain was useful, it provided contradictory information in two patients with hyperparathyroidism and 11 patients with normal glands. The results of Sudan IV staining should be interpreted with caution in evaluating the functional state of parathyroid glands.