Clinicopathologic Characteristics and Prognosis of Diffuse Sclerosing Variant of Papillary Thyroid Carcinoma in Japan: an 18-year Experience at a Single Institution

Background: Diffuse sclerosing variant (DSV) is a variant of papillary thyroid carcinoma that has diffuse involvement in one or both thyroid lobes without forming a dominant mass. We investigated the biological characteristics of DSV in Japan.

Methods: We investigated biological behaviors and prognoses of DSV in 35 patients who underwent surgical treatment between 1989 and 2007.

Results: After excluding papillary microcarcinoma, DSV accounts for 0.7% of papillary carcinoma. DSV occurs more frequently in younger patients and is clinically apparent as lymph node metastasis and lung metastasis more frequently than other papillary carcinomas, but the incidence of extrathyroid extension did not differ between the metastases. Routine radioiodine ablation therapy after initial surgery was not performed unless distant metastasis was clinically apparent at surgery. The disease-free survival rate of DSV was significantly worse than that of a pair-matched control group. However, only two patients, one with lung metastasis at surgery and another who underwent only palliative surgery, have died of carcinoma to date.

Conclusions: Although cause-specific survival of DSV was good, its disease-free survival was worse than that of the control group because of the unavailability of routine radioiodine ablation therapy. Therefore, DSV requires careful surgical resection to minimize the carcinoma recurrence.