Occult Papillary Thyroid Carcinoma With No Identifiable Intrathyroidal Primary: A Case Report and Pooled Analysis of...

Papillary thyroid carcinoma (PTC) rarely presents as cervical lymph node metastasis without an identifiable intrathyroidal primary despite exhaustive imaging and histopathologic evaluation, representing the rarest form of occult thyroid carcinoma and posing distinct diagnostic and therapeutic challenges. We report a 27-year-old man who presented with a cystic lateral neck mass. Fine-needle aspiration confirmed metastatic PTC, yet ultrasonography, computed tomography, and positron emission tomography/computed tomography demonstrated no thyroid abnormality. Total thyroidectomy with modified radical neck dissection revealed metastatic PTC in two of the 21 lymph nodes (pN1b) without extranodal extension, while exhaustive sectioning of the thyroid demonstrated only chronic inflammatory changes without carcinoma. At three months postoperatively, thyroglobulin was undetectable with no structural evidence of disease. To contextualize this presentation, we reviewed the literature and identified 22 comparable published cases of metastatic cervical nodal PTC without an intrathyroidal primary after total thyroidectomy, yielding a pooled cohort of 23 patients, including the index case. The pooled cases showed an atypical near-equal sex distribution (52% male), frequent lateral neck presentation (65%), cystic nodal morphology in 26%, benign or normal thyroid tissue in all patients, and BRAF V600E mutations in 63% of the minority tested. At a median follow-up of 24 months, 87% had no evidence of disease. These observations are most consistent with an occult thyroid carcinoma arising from an ultramicroscopic primary tumor or a regressed primary lesion. Persistent lateral neck masses, particularly when cystic, should prompt evaluation for metastatic PTC. Total thyroidectomy with appropriate nodal dissection enables definitive diagnosis and surveillance; radioactive iodine may be deferred in selected patients with an excellent response; and overall outcomes are favorable, supporting individualized management and lifelong follow-up.