Kc. Loh et al., Influence of lymphocytic thyroiditis on the prognostic outcome of patientswith papillary thyroid carcinoma, J CLIN END, 84(2), 1999, pp. 458-463
Both the association between lymphocytic thyroiditis (LT) and papillary thy
roid carcinoma (PTC), and the prognostic significance of lymphocytic infilt
rate in patients with thyroid malignancy, remain controversial. We examine
the above relationships by retrospectively reviewing our series of patients
treated for differentiated nonmedullary thyroid carcinoma at University of
California-San Francisco over a 25-yr period (1970-1995). Of the 631 patie
nts with complete data for analysis, 128 patients (20.3%) showed concomitan
t histologic evidence of LT and 503 patients (79.7%) had no evidence of LT.
Prognostic outcome was assessed using Kaplan-Meier survival plots and anal
ysis of risk factors by Cox's proportional-hazard modeling. The cohort with
LT revealed a higher frequency of PTC (97.7% vs. 87.3%) and female patient
s (85.2% us. 66.8%), a lower frequency of extrathyroidal invasion (7.8% us.
23.3%) and nodal metastases (25.8% us. 43.3%), and absence of distant meta
stases (0% vs. 4.8%), respectively, compared with those without LT. At init
ial surgery, a significantly greater proportion of patients with LT belonge
d to lower pathological tumor-node-metastasis stages, compared with those w
ithout LT (stage 1, 86.7% vs. 73%; stage 2, 4.7% vs. 8.3%; stage 3, 8.6% vs
. 15.3%; and stage 4, 0% us. 3.4%). Over a mean +/- SE follow-up period of
11.1 +/- 0.4 yr, patients with LT had significantly lower cancer recurrence
rate (6.3% vs. 24.1%; P < 0.0001) and cancer mortality rate (0.8% us. 8.0%
; P = 0.001), respectively, compared with those without LT. In summary, our
series showed a relatively common occurrence of LT in patients with PTC, a
nd we believed that lymphocytic infiltration developed mainly in response t
o the tumor itself. We also found a more favorable course of PTC in the pre
sence of LT; this supports the hypothesis that lymphocytic infiltration rep
resents a form of immune reaction to control tumor growth and proliferation
.