Endocrine Abstracts

Introduction: Despite its high vascularity, metastases to the thyroid is rare. The frequency of metastasis in routine practice is less than 0.2% of thyroid malignancies.

Clinical case: An ambulatory 48-year-old male presented with a two-month history of enlarging anterior neck mass that moves with deglutition, slowly growing in size, associated with hoarseness later in the course of the disease. He had no pertinent past medical history. Fine needle aspiration biopsy report: papillary thyroid cancer. CT scan was done and revealed a 5×3×5 cm mass occupying almost the entire thyroid gland, but protruding to the lumen of the trachea and obliterating the upper portion of esophagus. The patient underwent total thyroidectomy, laryngectomy with tracheostomy. Pathological examination revealed the presence of abundant mucus secreting agglomeration of large atypical cells. Findings were consistent with mucinous adenocarcinoma involving the right thyroid lobe, isthmus and larynx. There was noted lymph node metastasis involving 15 out of 19 level II to V neck lymph nodes. Immunohistochemistry showed that the tumor stained negative for thyroid transcription factor-1 and thyroglobulin. This is consistent with a metastatic tumor rather than a primary thyroid cancer. CK 7 was positive, CK 20 was negative, consistent with a pulmonary origin of the tumor. A PET scan was done a month after surgery, which showed extensive metastatic disease. There was noted FDG positivity of bilateral noncalcified pulmonary nodules, cervical lymph nodes at all levels, esophagus, liver, gastric wall and mesenteric soft tissue masses and nodules. Due to the widespread metastases he opted to be treated with palliative radiotherapy. Two months later, the patient died.

Conclusion: Metastasis to the thyroid is rare but may indicate extensive disease. In patients presenting with an anterior neck mass, an FNAB may not be sufficient to clinch the diagnosis and staining for specific cancer markers may be necessary.

References: Kummar, S, et al. “Cytokeratin 7 and 20 Staining for the Diagnosis of Lung and Colorectal Adenocarcinoma.” British Journal of Cancer 86.12 (2002): 1884–1887. PMC. Web. 27 Jan. 2018.

Shuanzeng W, et al. “Thyroid gland: other carcinoma, Secondary tumors/ metastasis ” 2003–2017, PathologyOutlines.com, Inc. Oct 2017.