Medullary carcinoma of the thyroid showing positive cytology in pleural effusion

A case report

Abstract

Cytologic findings in pleural effusions from a 38-year-old man with recurrent medullary carcinoma of the thyroid were described.
In Pap.test, malignant epithelial cells showed spindle or sometimes round cytoplasm, and round nuclei composed of loose clusters.
Occasionally, the tumor cells resembled mesothelial cells or macrophages. Malignant cells were characterized by coarse granular chromatin and cytoplasmic fine granules that stained red in Giemsa staining.
PAS-positive granules were located in peripheral cytoplasm, and no Congo-red-positive particles were present.
Immunocytochemical staining of carcinoembryonic antigen (CEA) was especially useful for differential diagnosis.