Figure 1  (A) Parathyroid imprint cytology showing the typical evenly stained round nuclei (May-Grünwald-Giemsa stain). (B) A typical parathyroid adenoma with a tan cut surface and a thin rim of fat. (C) A thinly encapsulated parathyroid adenoma (left) with adjacent background parathyroid tissue (haematoxylin and eosin (H&E) stain). (D) Nodular parathyroid hyperplasia showing multiple non-encapsulated nodules (H&E stain). (E) Nodular parathyroid hyperplasia showing a combination of chief and oxyphil cells (H&E stain). (F) A parathyroid carcinoma showing invasion through its capsule and into the adjacent thyroid tissue (H&E stain). (G) A parathyroid carcinoma showing the striking nuclear monomorphism often seen in these lesions (H&E stain). (H) Dense fibrosis and haemosiderin accumulation accompanying cystic and degenerative changes in parathyroid hyperplasia.