About 20% of patients with colorectal cancer have metastases at diagnosis. The most common sites are: liver, lung, peritoneum. However other sites can be affected, and the thyroid gland is one of them. Metastases to the thyroid gland are uncommon. Lung cancer, renal cell carcinoma, followed by breast cancer are the most frequent sites of primary tumors that can metastasise to the gland. Colon cancer metastases to the thyroid are very rare but surgeons must be aware of such possibility.
In this setting, Inês Coelho et al. from Surgery C Department of Centro Hospitalar e Universitário de Coimbra - Hospital Geral (Covões), published this year in the "International Journal of Surgery Case Reports" a paper reporting one of those rare cases. From reading this paper several important ideas emerge that surgeons treating colorectal cancer should know.
According to the authors, the majority of cases (75%) of thyroid gland metastases from colorectal tumors occur in stage III or IV colon cancer. Additionally, the diagnosis is usually made within 6 months to 8 years after colon resection. This emphases the importance of long term follow-up. Even though, metastases to the thyroid gland can be the first presentation of colorectal cancer. Metastases to the thyroid can be presented as a solitary cervical nodule and increased tumor markers. However, an increased thyroid uptake in a PET scan can be the only sign, which led some authors to advocate its use in the initial staging of colorectal cancer. Image exams are crucial for diagnosis, but only fine needle aspiration cytology can make a correct diagnosis.
Inês Coelho et al. make some important statements about how to treat this pathology. Treatment is not unanimous. Surgical resection prevents asphyxiation and emergent tracheostomy, but extend of resection is controversial. Since lymph node involvement is rare, radical cervical lymph node dissection is not routinely recommended. Treatment must be adapted to each patient, because in most of the cases other organs are concomitantly involved with secondary lesions. Surgeons must not forget that chemotherapy has no good results in thyroid gland metastases, and radiotherapy is indicated in life-threatening symptoms. Prognosis is bad.
The authors conclude stating that "the possibility of metastases should be considered in patients presenting a solitary thyroid nodule and a past history of cancer". Additionally, "a low threshold of suspicion is crucial to make a timely diagnosis of thyroid metastases from colorectal cancer."
Read this paper for more information, and do not forget to look for metastases in rare sites while treating colorectal cancer. If they are rare they do exist...
Link to PubMed:
Dr. Carlos Eduardo Costa Almeida
General Surgeon