Curious Residents of the Thyroid Gland: Two Case Reports of Colorectal Carcinoma Metastasis by Fine-Needle Aspiration Diagnosis

• Published in: Acta cytologica Vol. 62; no. 5-6; p. 443
• Main Authors: Melis, Céline, Ballaux, Florence, Bourgain, Claire
• Format: Journal Article
• Language: English
• Published: Switzerland 01.01.2018
• Subjects: Adenocarcinoma - chemistry; Adenocarcinoma - secondary; Adenocarcinoma - surgery; Adenocarcinoma, Follicular - chemistry; Adenocarcinoma, Follicular - pathology; Adenocarcinoma, Follicular - surgery; Aged; Biomarkers, Tumor - analysis; Biopsy, Fine-Needle; Colorectal Neoplasms - chemistry; Colorectal Neoplasms - pathology; Disease Progression; Fatal Outcome; Female; Humans; Immunohistochemistry; Keratin-20 - analysis; Male; Middle Aged; Predictive Value of Tests; Thyroid Neoplasms - chemistry; Thyroid Neoplasms - secondary; Thyroid Neoplasms - surgery; Thyroidectomy; Treatment Outcome; Tumour-to-tumour metastasis; Fine-needle aspiration; Thyroid
• ISSN: 1938-2650
• DOI: 10.1159/000490367

The most frequent metastases to the thyroid originate in the kidney, lung or breast. Colorectal adenocarcinoma represents less than 4% of metastases to the thyroid gland. Solitary metastases of colorectal cancer with no other manifestation of disseminated cancer disease are exceedingly rare. Within the Bethesda Classification for Reporting -Thyroid Cytopathology, metastases are included in Diagnostic Categories "Suspicious for Malignancy" and "Malignant." We present 2 cases of colorectal adenocarcinoma metastatic to the thyroid gland, diagnosed by fine-needle aspiration (FNA). One metastasis occurred in normal thyroid parenchyma; the other was a tumour-to-tumour metastasis into a follicular carcinoma of the thyroid. The latter is the first published tumour-to-tumour metastasis of a colorectal carcinoma in the thyroid from which both components were diagnosed by FNA. Diagnosing a metastasis to the thyroid is challenging. On FNA, a dual cell population should raise suspicion. Immunocytochemical and molecular analysis may be helpful. Clinical information is essential in guiding specific ancillary technique panels in scant cellular material.