Marginal vacuoles in metastatic thyroid carcinoma: a case report

A case of metastatic follicular carcinoma to the iliac bone in a 78-yr-old woman is presented. Fine-needle aspiration biopsy (FNAB) smears showed numerous, cohesive tumor cell groups with moderately abundant cytoplasm and distinctive, peripherally situated pink-staining vacuoles on May-Grünwald-Giemsa stain. The presence of marginal vacuoles strongly suggested the possibility of metastatic thyroid carcinoma. Immunohistochemical studies performed on a concomitant needle core biopsy showed immunoreactivity for thyroglobulin, supporting a thyroid derivation for this metastasis. To our knowledge, this is the first reported case in which marginal vacuoles ("flame cells") have been identified in a malignant thyroid condition.