Md Shahrier Amin,
PGY2, Anatomical Pathology
Case Three
Overview
Clinical history: 67 year old female presents with difficulty in swallowing for a few weeks and a multinodular goitre with two dominant nodules. FNAC is nondiagnostic due to inadequate follicular cells and subsequently hemithyroidectomy was done due to increasing dysphagia.
Discussion and answer
Gross examination shows a pale tan, hemorrhagic, well circumscribed nodular area with cystic changes in the hemithyroid. epithelium. Microscopic examination shows diffuse multinodular goiter and two other lesions: a) A cystic, hemorrhagic area consisting of masses of cells having clear cytoplasm and vesicular nucleus with prominent nucleoli. The cells are positive for RCC and CD10 but negative for TTF1 and CK7. b) A few cells having grooved nuclear membranes and orphan Annie type nucleus but not forming any papillary structures.
She was diagnosed with metastatic renal cell carcinoma (clear cell variant) to thyroid and an occult sclerosing type of papillary carcinoma.
Metastases to thyroid are usually rare. Clear cell renal carcinoma is the most frequent primary tumor metastasizing to the thyroid. It is unclear why RCCs often spread to the thyroid. The thyroid metastasis can be the initial manifestation, a sign of distant spread or recurrent disease. Time interval between resection of an RCC and thyroid metastasis can also be variable. Immunohistochemistry with RCC, CD10 and TTF1 can be used to differentiate between a clear cell type of thyroid carcinoma and metastatic RCC to thyroid.
In the current case, the patient had a history of right radical nephrectomy for a grade-2/4 RCC with IVC extension ~ 8 years ago. Occult sclerosing type of papillary carcinoma was an incidental finding, and an example of tumor to tumor metastasis.
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