Background: Intrathyroid metastases (ITM) of extrathyroid cancer are rare and have a poor prognosis. The aim of this work was to identify the sites of primary cancers and the treatment and prognosis of these lesions.
Study design: This retrospective study was carried out on patients treated between 1982 and 2002 in the surgical departments of the University hospitals of Poitiers, Limoges, Tours, and Nantes, France. All diagnoses were confirmed by cytology or histologic examination.
Results: Twenty-nine patients (41 to 78 years) had ITM. Primary cancers were renal cell in 16 patients, lung in 4, digestive in 4, sarcoma in 1, melanoma in 1, neuroendocrine in 1, and of unknown origin in 1 patient. For 10 patients, diagnoses of primary cancer and ITM were synchronous. For 19 patients, delay between diagnosis of the primary cancer and ITM was 6.8 years (2 months to 16 years). Diagnosis was confirmed with fine-needle aspiration 3 times and with histologic examination of the thyroid 26 times. Twenty-seven patients had thyroidectomy; two were not operated on. After treatment of ITM, 13 patients had new metastatic sites. Mean followup for all patients was 2.3 years. Seven patients (24%) (6 with renal cancer) were disease free (followup 4.5 years). Four patients were alive with disease (followup 1.4 years). Eighteen patients (62%) died of their disease at a mean delay of 1.4 years.
Conclusions: ITM are rare but the diagnosis should be borne in mind when patients have a history of cancer (mainly renal cancer). Preoperative diagnosis and complete evaluation could avoid unnecessary thyroidectomy because numerous patients had diffuse metastases.