Correspondence /

Encapsulated Follicular Variant of Papillary Thyroid Carcinoma

To the Editor

The January 2002 issue of the Journal includes 2 editorials and 1 review article regarding the controversies in the diagnosis of encapsulated follicular variant of papillary thyroid carcinoma.^1-3 We recently encountered a case that we believe addresses the issues and concerns faced by many pathologists.

A 48-year-old man with a right supraclavicular mass sought care in March 2001. His relevant medical history included right-sided lobectomy in 1969, which was diagnosed as "atypical follicular adenoma of thyroid." The excised neck mass consisted of lymph nodes containing metastatic thyroid cancer; it was follicular patterned and contained psammoma bodies. The cells lining the follicles focally showed nuclear features of papillary thyroid carcinoma, consistent with metastatic papillary carcinoma. A follow-up completion thyroidectomy was performed; all tissue was submitted and was found to be negative for tumor.

The lobectomy slides from 1969 were retrieved and reviewed; these showed a partially encapsulated and circumscribed follicular-patterned nodule whose nuclear cytology was that of papillary thyroid carcinoma zImage 1z. In view of the lymph node metastases and the negative completion thyroidectomy, this lesion diagnosed in 1969 as "atypical follicular adenoma" was reclassified as an encapsulated follicular variant of papillary thyroid carcinoma.

We present this case to emphasize 2 points. As illustrated by the long-term (32 years) follow-up in this case, the majority of encapsulated follicular variant of papillary thyroid carcinomas confined to one lobe and without evidence of capsular and/or vascular invasion are slow-growing tumors. They have an excellent prognosis and probably can be cured by lobectomy or partial thyroidectomy alone.⁴ This "benign" clinical behavior and the complications of total thyroidectomy have led some experts to classify such lesions as "tumors of undetermined malignant potential" to prevent aggressive treatment.⁵ However, as Baloch and LiVolsi¹ pointed out previously, a drastic change in thyroid tumor terminology is not enough to prevent excessive surgery (total thyroidectomy) and treatment (radioactive iodine). We believe this can be accomplished only by documenting the indolent course of this tumor type with long-term follow-up data.

Regulations allow pathology slides to be discarded at 5 years after diagnosis; hence, many institutions do not save their pathology slides, and decades of follow-up are normally not available. Therefore, the data need to be collected prospectively. Were such studies to begin immediately, the information would be available only in the middle of the present century.

We ask the question: "What is the purpose of changing diagnostic terminology?" If it is to stay the hand of the surgeon and nuclear medicine physician who may be overtreating thyroid cancer by total thyroidectomy and radioactive iodine therapy, how do we predict the course in a patient such as ours? Until unequivocal predictive factors become available through evaluations such as molecular analyses and DNA microarrays, we still must rely on morphologic examination. Clinicians follow standardized treatment protocols based on morphologic diagnoses and recommend therapy based on data amassed from the literature. In the absence of readily definable and testable predictive markers and of follow-up data, changing the diagnostic categories may only confuse the therapists.

We agree that many thyroid cancers are overtreated (and these are not only those with a follicular pattern), but to prove this in a scientific manner, we need to perform the appropriate long-term, controlled clinical and therapeutic trials and produce valid data. That will form the basis for more appropriate therapies for well-differentiated thyroid cancer.

Zubair Baloch, MD, PhD

Virginia A. LiVolsi, MD

Department of Pathology and Laboratory Medicine

University of Pennsylvania Medical Center

Philadelphia

Walter H. Henricks, MD

Bruce A. Sebak, MD

Department of Anatomic Pathology

Cleveland Clinic Foundation

Cleveland, OH

References