Thyroid cancer after in vitro fertilization: a retrospective, non-consecutive case-series analysis

Although a firm association between fertility treatment and thyroid cancer has not been established, the widespread use of IVF, as a substantial reservoir of subclinical thyroid cancer disease and evidence suggesting an estrogen-dependent behavior may render thyroid cancer patients after IVF a distinct subpopulation of particular interest. Thus, a retrospective, non-consecutive case-series analysis of patients with history of thyroid cancer after in vitro fertilization was conducted. Twelve female patients with thyroid cancer who had previously undergone IVF treatment were identified within the cohort of thyroid cancer patients followed in our institution. All cases of thyroid cancer were papillary thyroid carcinoma (PTC) on histology and median tumor size (25th and 75th percentile) was 12 mm (7 and 17 mm). Thyroid cancer was diagnosed after a median of 4 years (2 and 6 years) from the last IVF cycle and at the time of diagnosis lymph node metastases were present in five patients (42%) and distant metastases where seen in four of them. Collectively, these data suggest that an aggressive pattern of PTC might be present in this distinct subpopulation. This preliminary observation may be explained, at least in part, by the delay in the diagnosis.