MODERATELY DIFFERENTIATED MEDULLARY CARCINOMA OF THE THYROID GLAND ( 4.5 CM) WITH CARCINOMA EXTENDING TO CAPSULAR MARGINS OF RESECTION. FOCAL ANGIOLYMPHATIC INVASION WAS IDENTIFIED WITH FOUR LYMPH NODES POSITIVE FOR METASTATIC SPREAD.
Malignant medullary carcinoma represents a neoplasm of endocrine C cells of the thyroid. Medullary carcinoma accounts for approximately 10% of all thyroid malignancies. The majority of cases are sporadic, but about 15% are familial. The MEN IIA and IIB are examples of this. In the former, there is medullary thyroid cancer, pheochromocytoma, and parathyroid hyperplasia. In type IIB, there is medullary thyroid carcinoma, pheochromocytoma, mucosal neuromas and skeletal abnormalities. Both are associated with defects in the ret oncogene located on chromosome 10 (1). The average age of presentation is 50 years in sporadic cases, but only about 20 in familial cases.
This particular medullary cancer showed many of the classic features of the tumor (2). The tumor was tan/brown with infiltrating borders and areas of calcification and necrosis. The microscopic appearance was even more classic. The neoplastic cells could be seen infiltrating the parenchyma of the thyroid in a nested, occasionally trabecular pattern. There surrounding stroma was pink and found to be Congo red positive, indicating amyloid deposition. The cellular features included uniform round nuclei with a punctuate chromatin pattern. Angiolymphatic invasion was also seen, which is common in these tumors.
Medullary carcinomas often stain positive for calcitonin, which is a highly sensitive marker. Also, CEA, LMW cytokeratin and neuroendocrine peptides may be found. This tumor was as previously noted cytokeratin, CEA, calcitonin positive strongly supporting the diagnosis.
The prognosis of medullary carcinoma varies considerably. The overall 5 year survival is about 60-70%. An age of less than forty is a good prognostic indicator. Pathological stage is the most important factor. Those without perithyroidal involvement or nodal involvement may have a 70% 5 year survival or even higher. Distant metastasis is a particular bad prognosticator with 90% mortality in 5 years (3).
Contributed by Raj Hari, MD