Omission of lateral lymph node dissection in medullary thyroid cancer without a desmoplastic stromal reaction

Abstract Background Medullary thyroid cancer can be subdivided during surgery into tumours with or without a desmoplastic stromal reaction (DSR). DSR positivity is regarded as a sign of disposition to metastasize. The aim of this study was to analyse whether lateral lymph node dissection can be omitted in patients with DSR-negative tumours. Methods This was a retrospective cohort study of a prospectively maintained database of patients with medullary thyroid cancer treated using a standardized protocol, and subdivided into DSR-negative and -positive groups based on the results of intraoperative frozen-section analysis. Patients in the DSR-negative group did not undergo lateral lymph node dissection. Long-term clinical and biochemical follow-up data were collected, and baseline parameters and histopathological characteristics were compared between groups. Results The study included 360 patients. In the DSR-negative group (17.8 per cent of all tumours) no patient had lateral lymph node or distant metastases at diagnosis or during follow-up, and all patients were biochemically cured. In the DSR-positive group (82.2 per cent of all tumours), lymph node and distant metastases were present in 31.4 and 6.4 per cent of patients respectively. DSR-negative tumours were more often stage pT1a and were significantly smaller. The median levels of basal calcitonin and carcinoembryonic antigen were significantly lower in the DSR-negative group, although when adjusted for T category both showed widely overlapping ranges. Conclusion Lymph node surgery may be individualized in medullary thyroid cancer based on intraoperative analysis of the DSR. Patients with DSR-negative tumours do not require lateral lymph node dissection. In patients with medullary thyroid cancer, lymph node surgery may be individualized based on intraoperative diagnosis of desmoplastic stroma reaction (DSR). DSR-negative tumours develop neither lymph node nor distant metastasis and therefore do not require lateral lymph node dissection. No risk of recurrence