Invasive Papillary Cancer of the Thyroid*

SEVERAL pathologists—friends of ours, we hope—have noted the misleading title of this paper. They quite properly point out that papillary cancers of the thyroid are usually unencapsulated and that blood vessel invasion is common and may on occasion be demonstrated in lesions only a few millimeters in diameter. It is well known that many papillary cancers are small, are embedded within the gland substance, and fail to show gross evidence of either infiltration of neighboring structures or metastasis to the regional nodes. The clinical course of most of these tumors is so sluggish and prolonged as to give rise to misleading concepts concerning the clinical course of papillary cancers as a group. It should be stressed that such physical characteristics do not necessarily influence the ability of these tumors to metastasize to regional nodes or, for that matter, to distant sites. In fact such metastases are often the initial and only complaint of the patient for years prior to the discovery of the primary tumor and, hence, the formerly widespread misconception of the so-called “aberrant thyroid” tumors.