Significance of prophylactic paratracheal lymphnode dissection in a case of retrosternal goitre: a case report.

An elective or a prophylactic lymph node dissection is the removal of the lymph nodes that are normal on physical examination and on radiographic imaging. This type of dissection is not based on the visible disease in the targeted nodal basins, but on the potential of a radiographically occult tumour which can exist. The pathologic results of an elective lymph node dissection may help in predicting the risk of a future recurrence and, in some solid tumours, guide the delivery of the adjuvant therapy and as in this case, may contribute to a pathological diagnosis. The decision to proceed with an elective node dissection is based on the assessment of the risks and benefits of the procedure. The morbidity of the regional lymph node dissection must be balanced against the potential benefit of the procedure. A thyroid papillary microcarcinoma is defined according to the WHO criteria and Shaha as a thyroid tumour which is smaller than 1-1.5cm. Different terms are currently used to define this thyroid cancer such as small, tiny, minute, minimal or occult papillary carcinomas of the thyroid, impalpable thyroid carcinoma and incidental thyroid papillary cancer. A common clinical scenario is the incidental diagnosis of papillary thyroid microcarcinoma (PTMC) on the histology of the resected thyroid, following the surgery which was done for a presumably benign thyroid disease. PTMC was diagnosed in 7.1% of the patients with a presumably benign thyroid disease. It may be possible that this is an underestimation of the true incidence, because we did not use the serial sectioning technique and maybe because the PTMC which was present was so small that it was grossly not identified and sectioned. Herein, a case which was clinically suspicious and was radiologically and cytologically diagnosed as a case of retrosternal multinodular goitre underwent a near total thyroidectomy and a paratracheal lymphnode dissection. The node was found to have micrometastasis of the follicular variant of a papillary carcinoma and the thyroid, on a retrospective step sectioning, revealed an incidental PTMC. This case has been presented, to highlight the possibility of an incidental PTMC in the thyroid cases which were resected for benign disease and the importance of elective lymphnode dissection in contributing to the diagnosis of PTMC.