Oncocytic
tumors of the endocrine system are a group of rare entities described in several organs, including the thyroid gland.
Medullary carcinoma can seldom show the predominance of cells with oncocytic changes but the positive immunostaining for
calcitonin should be helpful for the correct diagnosis. We describe the case of a 71 year-old female Caucasian patient, with a hard 5 cm
thyroid nodule for 2 months. There was no significant cervical
adenopathy.
Thyroid hormone levels were normal. The US-Doppler examination showed a centrally vascularized nodule. Cytopathology analyses was suspicious for follicular
neoplasm with predominance of oncocytic cells, and a hemithyroidectomy was performed. Frozen section examination confirmed a follicular
neoplasm and the definitive histopathological and immunohistochemical analyses was conclusive for a
medullary carcinoma, oncytic variant. A total
thyroidectomy was then performed, followed by adjuvant 131Iodine
therapy. After a 40-month follow-up the patient is alive with no evidence of disease.
Medullary carcinoma should be considered in the differential diagnosis of unusual
thyroid carcinomas with predominance of cells with oncocytic changes.