If a solitary intrathyroid tumour is found at operation, the surgeon may either carry out a lobectomy plus an isthmectomy and await the routine histology report, or send the lobe for frozen-section diagnosis. In the latter situation, the pathologist can usually rule out non-neoplastic lesions and positively recognise papillary carcinoma, provided that papillae are present in the sections taken. It is not necessarily possible with frozen sections to distinguish between adenomas and microangioinvasive follicular carcinomas but, with experience, medullary carcinomas can be recognised. Routine use of paraffin wax-embedded blocks allows much greater sampling of the tumour and more time for microscopy, and the histology of routine preparations is considerably easier to interpret than that of frozen sections.
