Desmoplastic stromal reaction in medullary thyroid cancer - An intraoperative "marker" for lymph node metastases

Background: Medullary thyroid cancer (MTC) disseminates early to lymph nodes (LN). There is no pre- or intraoperative marker to exclude LN involvement and thereby avoid lateral neck dissection in LN-negative patients. Materials and Methods: This study was intended to verify the observation that patients with MTC lacking desmoplastic stromal reaction (DSR) never have LN metastases. In 120 patients undergoing primary operation for sporadic MTC the prognostic value of DSR with respect to LN involvement was evaluated. Results: Thirty-two (27%) of 120 tumors were DSR negative, and 88 (73%) were DSR positive. All 32 (100%) DSR-negative tumors were LN negative (N0), and all patients were biochemically cured. Of 88 DSR-positive tumors, 57 (65%) were staged N0, and 31 (36%) were staged N1(LN positive; Fisher's exact test: P = 0.0001). In a comparison of the LN involvement to the DSR characteristics, 32 (36%) of the 89 N0 patients and none of the 31 N1 patients were DSR negative. The sensitivity of DSR in predicting N0 is 38% (95% confidence interval: CI 95% = 27 %-55%), the specificity is 100% (CI 95% = 88%-100%). The sensitivity and specificity for the parameter DSR to differentiate between N0 or N1 were 100% and 36%, respectively. Conclusions: The desmoplastic stromal reaction appears to be an excellent intraoperative marker to predict LN involvement with a high specificity but low sensitivity. We therefore propose to avoid initial lateral neck dissection in MTC patients without DSR.