Thyroid metastasis from adenoid cystic carcinoma of the lung: a case report and literature review

Radiotherapy for primary thyroid adenoid cystic carcinoma

Primary thyroid adenoid cystic carcinoma (PTACC) is an extremely rare type of mucin-secreting adenocarcinoma. Currently, it is difficult to diagnose, and it lacks standard treatment protocols. We report the case of a 53-year-old female patient with PTACC who underwent additional intensity-modulated radiotherapy 1 month after surgical treatment with an uneventful course. No invasion or distant metastasis was detected at the 7-month follow-up after radiotherapy, and the prognosis was favorable. In this case, herein, we have summarized the diagnostic features of the disease and proposed that postoperative adjuvant radiotherapy can significantly improve the patient's prognosis. Finally, we further confirmed the important role of radiotherapy in PTACC by reviewing relevant literature, which may provide clinicians with valuable treatment experience.

Clinicopathological and Molecular Features of Secondary Cancer (Metastasis) to the Thyroid and Advances in Management

Secondary tumours to the thyroid gland are uncommon and often incidentally discovered on imaging. Symptomatic patients often present with a neck mass. Collision tumours of secondary tumours and primary thyroid neoplasms do occur. Ultrasound-guided fine-needle aspiration, core-needle biopsy, and surgical resection with histological and immunohistochemical analysis are employed to confirm diagnosis as well as for applying molecular studies to identify candidates for targeted therapy. Biopsy at the metastatic site can identify mutations (such as EGFR, K-Ras, VHL) and translocations (such as EML4-ALK fusion) important in planning target therapies. Patients with advanced-stage primary cancers, widespread dissemination, or unknown primary origin often have a poor prognosis. Those with isolated metastasis to the thyroid have better survival outcomes and are more likely to undergo thyroid resection. Systemic therapies, such as chemotherapy and hormonal therapy, are often used as adjuvant treatment post-operatively or in patients with disseminated disease. New targeted therapies, such as tyrosine kinase inhibitors and immune checkpoint inhibitors, have shown success in reported cases. A tailored treatment plan based on primary tumour features, overall cancer burden, and co-morbidities is imperative. To conclude, secondary cancer to the thyroid is uncommon, and awareness of the updates on diagnosis and management is needed.