Fig. 20.15A ). The microscopic hallmarks of papillary neoplasms include the following:
Fig.
20.15B ). In most cases, the epithelium covering the papillae haswell-differentiated, uniform, orderly cuboidal cells, but morepleomorphic or even anaplastic morphologies may be seen.
Fig.20.15Papillarycarcinomaofthethyroidgland.(AtoC)Apapillarycarcinomawithgrosslydiscerniblepapillarystructures.Inthisparticularexample,well-formedpapillae(B)arelinedbycellswithcharacteristicempty-appearingnuclei,sometimestermedOrphan Annie eye nuclei(C).(D)Cellsobtainedbyfine-needleaspirationofapapillarycarcinoma.Characteristicintranuclearinclusionsarevisibleinsomeoftheaspiratedcells(arrows). (Courtesy of Dr. S. Gokasalan,Department of Pathology,University of Texas Southwestern Medical School,Dallas,Texas.)
Nucleiwithfinelydispersedchromatin,whichimpartsanopticallyclearoremptyappearance,givingrisetothedesignationground-glassorOrphanAnnieeyenuclei(see
Fig.
20.15B ).Inaddition,invaginationsofthecytoplasmoftengivetheappearanceofintranuclearinclusions(“pseudo-inclusions”)orintranucleargrooves(see
Fig.20.15D ).Thesenuclearfeaturesaresufficientforthediagnosisofpapillarycarcinoma,evenintheabsenceofpapillaryarchitecture.
Concentricallycalcifiedstructurestermedpsammomabodiesareoftenpresentwithinthelesion,usuallywithinthecoresofpapillae.Thesestructuresarealmostneverfoundinfollicularandmedullarycarcinomas.
Focioflymphaticinvasionbytumorareoftenpresent,butinvolvementofbloodvesselsisrelativelyuncommon,particularlyinsmallerlesions.Metastasestoadjacentcervicallymphnodesoccurinuptoone-halfofcases.
Thereareoveradozenvariantsofpapillarythyroidcarcinoma,themostcommonofwhichistheso-calledencapsulatedfollicularvariant,comprisedoffollicleslinedbycellsharboringnuclearfeaturesofpapillarycancers(discussedearlier).
Papillary carcinomas are nonfunctional tumors, so they manifest most often as a painless mass in the neck, either within the thyroid or as a metastasis in a cervical lymph node. A preoperative diagnosis usually can be established by fine-needle aspiration based on the characteristic nuclear features described earlier. Papillary carcinomas are indolent lesions, with 10-year survival rates in excess of 95%. Of interest, the presence of isolated cervical node metastases does not have a significant influence on prognosis. In a minority of patients, hematogenous metastases are present at the time of diagnosis, most commonly to the lung. The long-term survival of patients with papillary thyroid cancer is dependent on several factors, including age (in general, the prognosis is less favorable among patients older than 40 years of age), presence of extrathyroidal extension, and presence of distant metastases (stage).
Recent studies have shown that follicular variants of papillary carcinoma that lack evidence of invasion have essentially no potential for malignant behavior. In recognition of this, forthcoming recommendations from the World Health Organization suggest the name carcinoma should be stripped from these tumors, which will henceforth be classified as benign neoplasms to prevent overtreatment.