Clinical history: A 50-year-old lady presented with dysphagia, significant weight loss and a palpable thyroid mass. She was a smoker, and had a self-reported history of total thyroidectomy more than 2 decades ago.
Fine needle aspiration of the thyroid mass was performed.
- Highly atypical epithelial cells arranged in clusters
- Pleomorphic nuclei with irregular outlines, coarse chromatin and occasional small nucleoli
- Moderate to abundant cytoplasm
- Necrosis and atypical mitotic figures are seen
- Benign thyroid cells are present (first image)
The malignant cells show features of adenocarcinoma.
Elimination of “suspects” based on the options in the Bethesda System for Reporting Thyroid Cytopathology:
The appearance of the tumour cells is NOT typical of primary thyroid carcinoma (follicular carcinoma, papillary thyroid carcinoma, medullary thyroid carcinoma or anaplastic carcinoma).
Possible remaining options:
- Metastatic malignancy: This is the favoured diagnosis as a second distinct population of benign thyroid cells are admixed with the carcinoma (see below).
- Poorly differentiated carcinoma (of the thyroid): this is often associated with differentiated carcinoma, which we may consider given the patient’s self-reported history of a previous thyroid operation.
Note: Dysphagia may be seen in advanced thyroid carcinoma but is not common.
Possible primary sources of a metastatic adenocarcinoma to the thyroid to consider:
- Lung adenocarcinoma
- Renal cell carcinoma (not likely the clear cell type)
- Breast carcinoma (invasive carcinoma of no special type)
- Gastrointestinal tract/pancreatobiliary adenocarcinoma
Knowledge of relevant clinical history and immunocytochemistry on cell block would be very helpful in the DDx.
In view of the history of dysphagia and significant weight loss, the patient underwent an OGD, and a gastro-oesophageal junction tumour and a skip lesion proximally were seen.
Biopsy of the gastro-oesophageal tumour:
Biopsy of the gastro-oesophageal junction tumour and the skip lesion showed similar findings.
They both contained carcinoma which was composed of solid sheets and nests of tumour cells with focal gland formation.
The morphology of the carcinoma cells in the thyroid FNA sample was similar to that of this sample.
The tumour cells were positive for CK7 and negative for CK5/6.
Metastatic adenocarcinoma (oesophageal primary)
Case writer: Dr Wan Jing Tay
