Fine needle aspiration cytology of high grade mucoepidermoid carcinoma of the thyroid. A case report

BACKGROUND: Although mucoepidermoid carcinoma is considered a very rare, low grade thyroid neoplasm, in two patients a very rapid and aggressive outcome occurred. We describe the cytologic, histologic and immunohistochemical findings of a high grade mucoepidermoid carcinoma that evolved into an anaplastic carcinoma. CASE: A 57-year-old man was admitted with dysphagia, dysphonia and odynophagia. The patient had begun to develop symptoms over the previous two months. Ultrasound and computed tomography revealed diffuse enlargement of the thyroid gland with multiple, bilateral, palpable lymph nodes in the cervical, supraclavicular, paratracheal and retrocaval chains. The patient died four weeks after receiving the first cycle of treatment with adriamycin and cisplatin. The smears were highly cellular, with a background rich in neutrophilic, inflammatory infiltrate and necrotic debris. Two main types of tumor cell were identified: squamoid and mucus secreting. Squamoid cells were polygonal, with well-defined borders and dense cytoplasm. Nuclei varied greatly in shape and size and displayed clumped chromatin and prominent nucleoli. Mucussecreting cells were ring shaped and dispersed among the squamoid cells; they contained a large vacuole, with condensed acid and neutral mucins, that peripherally displaced the nucleus. Small and large clusters of large, polygonal cells with single or multiple bizarre nuclei and less-dense cytoplasm were also present. Histology revealed tumor cells distributed in irregular nests, with necrosis surrounded by a fibrous stroma. The predominant cells were squamoid, but dispersed mucus-secreting cells were frequently seen in the better-differentiated areas. Sparse anaplastic spindle cells were observed adjacent to the squamoid focus. Immunohistochemistry revealed a reaction positive for cytokeratin (AE3/AE1) in tumor nests and negative staining for thyroglobulin and neuroendocrine markers. CONCLUSION: Although mucoepidermoid carcinoma of the thyroid is a very rare neoplasm, its peculiar cytomorphologic features in fine needle aspiration cytology may contribute to its correct diagnosis.