Poorly differentiated thyroid carcinoma mimicking adenoid cystic carcinoma on aspiration cytology: a case report.

BACKGROUND

Spherical hyaline globules present a characteristic cytologic picture classically seen in salivary gland tumors. This pattern in fine needle aspiration cytology (FNAC) of thyroid malignancies is rare. Sporadic reports of papillary and follicular carcinoma with adenoid cystic pattern are described in the literature.

CASE

We report, to our knowledge, the first documented case of poorly differentiated thyroid carcinoma with adenoid cystic pattern on aspiration cytology. An 80-year-old man presented with a thyroid nodule of 3 years' duration. FNAC smears consisted predominantly of cells arranged around spherical hyaline globules resembling adenoid cystic carcinoma. Histopathologic examination showed a poorly differentiated thyroid carcinoma. Immunohistochemically, the tumor cells showed positive reaction for thyroglobulin and cytokeratin.

CONCLUSION

Poorly differentiated carcinoma of the thyroid presents a variable cytologic picture. Awareness of the cytomorphologic spectrum reduces the possibility of diagnostic error. Reliance on hyaline globules as the sole criterion results in erroneous diagnosis.