Thyroid papillary carcinoma. Pathological and philosophical controversies.

An encapsulated thyroid tumor with a papillary architecture is statistically much more likely to be a hyperplastic follicular adenoma than a papillary carcinoma, for the latter are uncommonly encapsulated. Hyperfunction of such a tumor is diagnostic of an adenoma. Various histopathologic features are useful in the differential diagnosis, but these are more accurately termed guidelines than criteria. The presence of psammoma bodies, fibrovascular stalks of papillae and pale nuclear changes are probably the most reliable histopathologic features of a carcinoma. The value of needle biopsy as a diagnostic tool for the screening of thyroid nodules is emphasized. Encapsulated variants of papillary carcinoma are discussed, including the rare pure follicular variant and those intermixed with adenomatous components, suggesting the possibility that some papillary carcinomas might arise in a preexisting adenoma. When the histopathologic diagnosis is equivocal, a benign interpretation is favored since encapsulated papillary carcinomas are very low grade, have an unusually favorable prognosis, and need no further resection. The polarization in past years of clinicians into radical and conservative operative fractions is reviewed. This stemmed from different interpretations of the presence of lymph node metastases in a majority of cases and the high frequency of intraglandular microscopic dissemination of neoplasm. It is clear that biological behavior of this unusual cancer is more important than a literal interpretation of the pathologic findings as a determinant for patient management. The surgical pathologist should be mindful that he plays an important role in patient management, not only by providing a diagnosis but also by serving as a consultant to the surgeon in pathologic correlation.