Coexisting chronic lymphocytic thyroiditis and papillary thyroid cancer revisited

The effect of chronic lymphocytic thyroiditis (CLT) on the behavior of papi llary thyroid cancer (PTC) remains unclear. In recent studies the presence of CLT in patients with PTC was reported to be associated with a lower recu rrence rate and an improved survival rate. Furthermore, patients with PTC a nd tumor infiltrating lymphocytes (TILs) have been reported to have lower r ecurrence rates and a lower frequency of distant metastases, Because of the se and other observations, a tumor immune response in PTC has been suggeste d. The aim of our study was to determine: (I) the relative frequency of CLT in PTC: (2) the prognostic significance of CLT in patients with PTC; and ( 3) if TIL occurs independently or in association with CLT. A 10-year retros pective study of patients who underwent initial thyroidectomy for PTC from 1986 to 1996 was completed. The extent of thyroid lymphocytic infiltration was determined within the tumor, surrounding the tumor, and in the distant parenchyma by two independent observers blinded to the clinical data. Dense focal/diffuse lymphoid aggregates throughout the thyroid gland were diagno stic of CLT and when present within or surrounding the tumor were designate d TILs. A total of 136 patients with PTC (typical and follicular variant of PTC histologic subtypes) were identified with a mean follow-up of 4.4 year s and a 8% mortality rate at 10 years. Thirty percent of the patients with PTC had coexisting CLT, and 65% of these patients with CLT had positive ant i-thyroglobulin antibodies. Patients with coexisting CLT and PTC were young er (p < 0.05), more likely to be female (p < 0.05), and more likely to have multicentric tumors (p < 0.001) compared to patients without CLT. Only 5% of patients had TILs without CLT, but 82.5% of patients with CLT had TILs i dentified (p, < 0.0001). By univariate analysis CLT, age, gender, stage of PTC, tumor multicentricity, and tumor size were significant prognostic fact ors. Only age and TNM stage of PTC remained independent prognostic factors by multivariate analysis. We found a similar frequency (30%) of coexisting CLT and PTC as reported by others: but, more importantly, the presence of T ILs primarily occurred in association with CLT. The presence of CLT in pati ents with PTC correlated with an improved prognosis. It was not an independ ent prognostic factor, however, and was not associated with a lower recurre nce rate or a lower frequency of distant metastasis.