Occult thyroid microcarcinomas in benign thyroid disease

Abstract

Over the past few years, incidental thyroid microcarcinoma has become a frequent disease, and its reported incidence is considerable. Discovering new cases depends on the extended indications for total thyroidectomy for benign disease, on progress in the field of diagnostic instruments (ultrasound, scintigram, fine needle biopsy for cytology, CT scan, MRI, PET), and on the pathological examination of very thin slices of specimens. In spite of the high incidence reported in some autopsy series, which suggests that this tumour may have a good prognosis, some Authors report an overall incidence of up to 11% of local recurrence, metastasis or mortality. For all these reasons, the surgical treatment of incidental thyroid microcarcinoma is still controversial. The aim of this study was to estimate the prevalence of incidental thyroid microcarcinoma and examine the clinical-pathological findings of incidental thyroid microcarcinoma. A total of 199 operative findings derived from total thyroidectomy that were recorded between January 2012 and December 2015 were assessed from the point of view of a histopathology. The histological diagnosis was made by a pathologist according to the recommendations of the World Health Organization (WHO) through an assessment of sections of the thyroid gland that were no more than 2 mm thick. Following these routine histological examinations, 28 cases (14,07%) of “incidental” thyroid microcarcinoma were found. The mean tumour size was 4.10 mm (range: 0.12 mm to 10 mm). The tumours were multifocal in two patients, and none of them presented lymph node metastases. Thyroid microcarcinoma is a malignant tumour associated with a good prognosis. Multifocality should be the main factor considered in selecting the type of thyroid surgery. A total thyroidectomy may be regarded as sufficient treatment for this condition.