Identification of occult metastases of medullary thyroid carcinoma by calcitonin measurement in washout fluid from fine needle aspiration of cervical lymph node.

Medullary thyroid carcinoma (MTC) may occur sporadically or as a manifestation of an autosomal-dominant inherited syndrome, the multiple endocrine neoplasia type 2. DNA-based RET genotype analysis gained worldwide acceptance in the identification of asymptomatic gene carrier. MTC synthesize and secrete calcitonin, a well established tumor marker and postoperative level of serum calcitonin, indicates whether residual disease was left behind and whether reintervention is necessary. However, management is difficult when routine imaging studies for MTC are negative. This paper brings a report of an illustrative case of a patient with MTC diagnosed by molecular screening, who persisted with detectable levels of serum calcitonin after surgical procedure. After 48 months, an increase in serum calcitonin impelled us to investigate the disease focus. Cervical-US and calcitonin measurement in washout fluid from fine needle aspiration was successfully used to identify MCT metastasis in a lymph node, allowing appropriated reintervention and illustrating the potential clinical applicability of this method.