Pre-operative diagnosis of thyroid cancer: clinical, radiological and pathological correlation

Ultrasonography and fine-needle aspiration biopsy (FNAB) are the mainstays of diagnosing thyroid cancer accurately and reducing the number of diagnostic lobectomies. No benchmark for diagnostic accuracy has been published in the South African context. This single-institution study addresses this deficit.

The oncology, pathology and surgical records of all patients diagnosed with thyroid carcinoma from 2004 to 2010 at Groote Schuur Hospital, Cape Town, South Africa, were reviewed and data were recorded on a standardised confidential proforma. The findings on pre-operative clinical assessment, ultrasound and FNAB were correlated with the histopathology results. Diagnostic accuracy for thyroid cancer was determined by correlating pre-operative investigations with the final diagnosis. Sensitivity of ultrasound and FNAB were calculated.

A total of 109 patients, 79 female and 30 male, were identified. The majority (99, 90.8%) had well-differentiated thyroid cancers (56 papillary, 30 follicular, 10 mixed and 3 Hurtle cell carcinomas). There were 6 anaplastic and 4 medullary carcinomas. Of the 109 patients 38 had a definite pre-operative diagnosis, in 61 a malignant tumour was suspected, and 10 had surgery for benign disease. FNAB was inadequate in 11 cases and the findings indicated a benign lesion in 47, a suspicious lesion in 13 and a malignant lesion in 38 patients diagnosed with thyroid carcinoma. FNAB diagnosed all patients with medullary and anaplastic carcinoma but less than half of those with well-differentiated thyroid carcinoma. Ultrasound scans detected at least one suspicious feature in 44 patients. Microcalcification was the most common sign.

The rate of pre-operative diagnosis of well-differentiated thyroid carcinomas in this unit is under 50%, well below international norms. Our standard practice needs to change to include ultrasound-guided FNAB and standardised reporting of high-resolution ultrasound and cytology, before reassessment of our diagnostic accuracy.