Enhancing Detection of Medullary Thyroid Cancer in Cytologically Indeterminate Thyroid Nodules: The Role of Molecular...

Medullary thyroid cancer (MTC) is a rare neuroendocrine tumor arising from the parafollicular C-cells. Unlike follicular-derived thyroid cancers, the only curative treatment modality for MTC is complete surgical resection which makes early detection essential. Fine-needle aspiration biopsy of the thyroid is an accurate preoperative diagnostic method; however, morphologic heterogeneity, sample quality and cytomorphologic overlap with other entities may result in misclassification, with potential for delays in treatment and poorer outcomes.

Retrospective review of 4 cases with histologically confirmed MTC, in which the initial cytological diagnosis was not indicative of MTC.

Four patients diagnosed with MTC within the past 6 years are included in this report. The age at diagnosis ranged from 36 to 64 years. Thyroid ultrasound demonstrated a solitary nodule in 3 cases and a multinodular thyroid in one. Fine needle aspiration cytology was signed off as suggestive of oncocytic (Hürthle) cell neoplasm in 2 cases, atypia of undetermined significance in one and suggestive of follicular neoplasm in the fourth case. The diagnosis of MTC was established by molecular testing in all patients, and preoperative serum calcitonin was consistent with the diagnosis. All patients had histologically confirmed MTC.

This case series highlights the heterogenous presentation of MTC in cytology samples. In cases with indeterminate cytology, additional diagnostic tools, particularly molecular testing, should be considered to improve diagnostic accuracy and surgical management.