Aggressive fibromatosis of the neck initiated after thyroidectomy

We describe the case of a 44-yr-old woman, who 2 yr after thyroidectomy for a multinodular goiter with a follicular adenoma showed a rapidly growing mass of the neck causing dysphagia and moderate pain. Fine needle aspiration biopsy revealed the presence of fibroblast-like cells, partially with atypical features and no colloid: the cytological diagnosis was suspicious for an indeterminate (mesenchymal) neoplasm. Histological diagnosis, after extensive surgery, indicated aggressive fibromatosis. Immunohistochemistry was positive for vimentin and negative for thyroglobulin. After surgery, nuclear magnetic resonance showed a persistent mass of approximately 2 cm; dysphagia and pain persisted. Therefore, the patient received external radiation therapy (total dose 60 Gy) with clinical benefit. The patient is without symptoms 1 yr after surgery.