Sentinel lymph node biopsy useful in thyroid carcinoma

NEW YORK (Reuters Health) - Sentinel lymph nodes in differentiated thyroid carcinoma are "a highly significant predictor" of the status of non-sentinel nodes, according to a report in the December Archives of Otolaryngology-Head and Neck Surgery.

Sentinel lymph node biopsy (SLNB) - the standard for identifying breast cancer and melanoma metastases in regional lymphatics - also has "high accuracy, sensitivity, specificity, and negative predictive utility" in patients with differentiated thyroid carcinoma, the authors announce.

"Our findings enable us to confidently state" that if the sentinel nodes are negative, "then additional non-sentinel lymph nodes in the central compartment will also likely be negative," senior author Dr. Richard J. Payne from McGill University, Montreal, and colleagues report.

Dr. Payne and his associates evaluated the usefulness of sentinel lymph node biopsy in 98 patients with preoperative findings that were diagnostic or highly suggestive of differentiated thyroid carcinoma. All of them had total thyroidectomy and central compartment dissection.

Seventy-five patients had differentiated thyroid carcinoma (48 papillary carcinomas, 22 papillary microcarcinomas, 3 Hurthle cell carcinomas, and 2 follicular carcinomas). The remaining 23 patients had follicular or Hurthle cell adenomas or adenomatous nodules.

Sentinel nodes, identified with methylene blue dye, were collected from 60 of the 75 patients with malignant tumors; lymph node metastases were found in 15.

Non-sentinel nodes (i.e., nodes that didn't stain blue) were collected from 59 of the 75 thyroid cancer patients; in 6 of these patients, metastatic tumor foci were found, but these patients also had positive sentinel nodes.

The sensitivity, specificity, and positive and negative predictive values of sentinel node biopsy for predicting the status of non-sentinel nodes were 100%, 86%, 40%, and 100%, respectively, according to the authors.

They also report concordance between sentinel and non-sentinel node findings in 61 of 70 patients (87%), the investigators report.

"Sometimes there are as many as seven" sentinel lymph nodes, Dr. Payne told Reuters Health by email. "However, 3 is the most common number of lymph nodes that need to be examined."

"We are very excited about our most recent study, which has just been completed," in which pathologists were able to distinguish benign from malignant sentinel nodes "while the patient was still asleep on the table."

"As a result, patients with positive lymph nodes get a formal neck dissection, while the patients with negative lymph nodes do not require any further lymph node exploration/dissection," he continued. "This will avoid the complications associated with neck dissection in the majority of patients undergoing thyroidectomy."

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