Intracytoplasmic lumina in medullary carcinoma of the thyroid gland. Report of a case with cytologic and immunocytochemical features.

BACKGROUND: Intracytoplasmic lumina (ICL) have been observed frequently in breast carcinoma cells. However, they are extremely rare in thyroid gland tumors. We encountered a medullary carcinoma of the thyroid (MCT) with ICL and present a case with cytologic, immunocytochemical and ultrastructural features. CASE: A 15-year-old female was admitted with a left thyroid mass. Ultrasound examination revealed a well-defined tumor in the left lobe of the thyroid. Fine needle aspiration cytology showed mainly dispersed spindle cells with oval nuclei and some polymorphic or triangular tumor cells. The tumor cells containing ICL were noted at high magnification. The ICL contained sparse microvilli and abundant granular material with dense, round bodies on ultrastructural sections. Immunocytochemically, these tumor cells were positive for calcitonin and carcinoembryonic antigen (CEA). Moreover, CEA was recognized in the ICL with immunocytochemical staining. All tumor cells were negative for thyroglobulin. Pathologic examination confirmed the diagnosis of medullary carcinoma of the thyroid gland.
CONCLUSION: MCT can include ICL with granular material containing CEA.