Endocrine Abstracts

Background: CV-PTC is often indolent with excellent long-term response, while TCV-PTC (≥50% of tall cells) have aggressive features and worse clinical behavior. Less is known about the clinical behavior of CV-PTC with tall cells <50% (TC/CV-PTC) that, so far, is considered as low risk tumor.

Aim: To evaluate the histological presentation of CV-PTC, TC/CV-PTC, TCV-PTC and their clinical behavior after 6 years of follow up.

Methods: We evaluated the data of 610 consecutive patients affected by PTC, divided in: group A (CV-PTC; 417/610–68.4%), group B (TC/CV-PTC; 64/610–10.5%) and group C (TCV-PTC; 129/610–21.1%).

Results: No difference in gender, tumor dimension, multifocality, bilaterality, histological thyroiditis, central compartment lymph node dissection, pN1, number of metastatic lymph nodes and prevalence of ¹³¹I avid metastases at RRA, was found among the groups. Patients of group C were significantly older (P=0.02). Neoplastic emboli were more frequent in group B (23.4%) vs C (13.2%) and A (9.8%), while mETE in group C (73.6%) vs B (57.8%) and A (39.6%) (P<0.01). Low risk were prevalent in group A (50.4%) vs B (20.3%%) and C (0%) and Stage I was more frequent in group A (94.7%) and B (96.9%) vs C (82.2%) (P<0.01). In group A (87.1%), most patients were treated with lower activities of ¹³¹I (30 mCi) vs B (79.7%) and C (74.4%) (P<0.01). After 6 years, 18/610 (2.9%) were lost at follow up and the remaining were re-evaluated. No differences were found when considering excellent (ER) and indeterminate response (IR), while biochemical incomplete (BiR) was more frequent in group A (6.1%) vs C (4%) and B (1.6%), but above all, structural incomplete (StR) was more frequent in group B (13.1%) vs C (8.9%) and A (4.9%) (P<0.01). This difference is remarkable for CV/TC-PTC with tall cells 20–40% (14.5%) while CV/TC-PTC with tall cells <10% showed no StR. Moreover, no differences were shown in re-treatments performed during the follow up (i.e. surgeries or ¹³¹I).

Summary: 1) Older age, presence of neoplastic emboli and mETE were significantly more frequent in the TC-PTC and TC/CV-PTC with respect to CV-PTC; 2) After 6 yrs of follow up, BiR was more frequent in CV-PTC, while StR in TC-PTC but in particular in TC/CV-PTC.

Conclusion: The presence of tall cells, also if <50%, identifies a subgroup of PTC with an aggressive behavior and should be considered at intermediate-risk similarly to the conventional TC-PTC