<prompt> Diagnostic feature of parathyroid carcinoma is-CytologyMetastasisClinical featuresAll  <response>: Ans. b MetastasisRef: Robbins 9thpg 1104; 8thpg 1129Morphology in hyperparathyroidismParathyroid adenomasSolitary lesions withuniform, polygonal chief cells along with nests of oxyphil cells oxyphil adenomasPrimary hyperplasiaChief cell hyperplasia with abundant water-clear cells water-clear cell hyperplasia involving all 4 glandsParathyroid CarcinomasCircumscribed lesion in a single gland diagnosed by invasion of surrounding tissues and metastasis as the only reliable criteria. 