Abstract

We present a case of metastatic giant cell carcinoma of the thyroid in small intestine presenting as an unusual polypoid growth, and its ultrastructure and immunohistochemical reaction to thyroglobulin were investigated. The patient was a 63 years old female who received a segmental resection of ileum for intestinal obstruction, one year after a radical neck dissection and thyroidectomy for anaplastic (giant cell variant) carcinoma with a focus of papillary tumor of the thyroid. In the segmentally resected ileum, there were three conglomerated round intraluminal polypoid tumor masses in close approximation which measured 4.5 cm, 2.5 cm and 2 cm respectively. The histological features were similar to those of thyroid lesion, being predominantly made of anaplastic giant and spindle cells in haphazard arrangement. Ultrastructure of pleomorphic spindle cells and multinucleated giant cells demonstrated numerous mitochondria with tubular cristae, rough endoplasmic reticula and a few membrane-bound dense granules. Peroxidase-antiperoxidase method against thyroglobulin revealed strong positive staining on papillary carcinoma and weak positivity on both giant cells and spindle cells of the anaplastic carcinoma. The above observations confirm that multinucleated giant cells of small intestine originate from metastatic giant cell carcinoma of the thyroid.