The macrofollicular variant of papillary thyroid carcinoma: a study of 17 cases.

We report 17 cases of a distinctive variant of encapsulated papillary carcinoma that is likely to be confused with macrofollicular adenoma or nodular goiter. The tumors showed the unusual combination of macrofollicles and foci of the conventional follicular variant of papillary carcinoma. Macrofollicles occupied over 50% of the cross-sectional areas of the tumors. The macrofollicles were lined either by cells with large ground-glass nuclei, cells with large but less pale nuclei with stippled chromatin, or cuboidal cells with hyperchromatic nuclei. Solid foci were present in four tumors, and a focal insular growth pattern was noted in a fifth tumor. All patients were females ranging in age from 15 to 69 years (mean, 35.4 years). Despite the large size of the tumors (mean diameter, 4.8 cm), only two metastasized to cervical lymph nodes. One of these neoplasms showed extrathyroidal extension, while the other widely invaded the thyroid tissue through the tumor capsule. Multicentric foci of papillary carcinoma with a follicular nonsclerosing growth pattern were demonstrated in the contralateral lobe in two thyroid glands. All patients with follow-up were alive and symptom-free 2 months to 6 years following surgery.