Macrofollicular Variant of Papillary Thyroid Carcinoma: A Case and Control Analysis.

The planimetric, flow cytometric, and immunohistochemical characteristics of the macrofollicular variant of papillary thyroid carcinoma (MFVPTC) have not been reported before. The clinical, morphological, immunohistochemical, planimetric, and flow cytometric characteristics of six cases of the MFVPTC and six of the follicular variant of papillary thyroid carcinoma (FVPTC) were analyzed. Patients had undergone surgical treatment. The mean age was 38 (range 29-64 yr), and five were women. Tumors had a mean size of 3.2 cm (range 0.3-4.5 cm). Half were originally diagnosed as goiter. Macrofollicles had a mean diameter of 345.5 um, perimeter of 1237 um, and area of 13,779 um(2), with nuclear changes of PTC. Mean follow-up was 107 mo (range 12-277), and neither lymph node metastases nor recurrence were seen. Differences in diameter, perimeter, and area between the macrofollicular and follicular variants were found. Follicular neoplastic cells were thyroglobulin and 5-100 protein positive in macrofollicles and normofollicles. All were negative to cytokeratin and to high-mol-wt keratin. All tumors were diploid. There were no significant differences in follow-up, DNA content, nor immunohistochemical reactivity. Differences in diameter (p < 0.00006), perimeter (p < 0.0001), and area (p < 0.001) were observed. It is important to recognize this variant because it could be misdiagnosed as benign thyroidal lesions.