Intraocular metastasis of medullary thyroid carcinoma investigated by transscleral fine-needle aspiration. A case report and review of the literature.

Medullary thyroid carcinoma occurs in a sporadic setting and may also be inherited in an autosomal dominant fashion, which is related with germline mutations of the RET gene. Metastases are often present at the time of a diagnosis-most frequently within the cervical lymph nodes, followed by the liver, lungs, and bones. Intraocular metastases are extremely rare. We present a case of choroidal metastasis as a first presentation of disease progression in a patient with Multiple Endocrine Neoplasia type 2A syndrome (MEN2A) who had undergone thyroidectomy 33 years earlier for medullary thyroid carcinoma. Transscleral aspirate smears showed necrotic malignant cells suggesting amelanotic malignant melanoma or metastatic neuroendocrine tumor. The similar cells were found on parotid fine-needle aspiration. The diagnosis of metastatic medullary thyroid carcinoma was definitely established on the parotidectomy specimen based on its characteristic morphological and immunohistochemical features. This is the only case of ocular metastasis from medullary thyroid carcinoma found in the English literature that was investigated by pathological examination using transscleral fine-needle aspiration biopsy.