Endocrine Abstracts

Introduction: Differentiated thyroid carcinoma (DTC) can often be multifocal. However, the multifocal character as associated with a more pejorative prognosis remains controversial. The objective of our study is to describe the clinical, histological and evolutionary characteristics of multifocal DTCs.

Materials and methods: Retrospective study including 159 patients diagnosed with a multifocal CDT, treated at the endocrinology service of the University Hospital of Casablanca between 1986 and 2018. The statistical analysis was performed by the IBM SPSS Statistics 25 software.

Results: The average age of our patients was 47±13 years with a clear female predominance of 153 women against 6 men. All patients underwent total thyroidectomy. Only 6% underwent lymph node dissection. 88% of patients benefited from radioactive iodine treatment. Papillary carcinoma with follicular differentiation was the most common histological type found in 42% of patients, other histological variants were found including classical papillary carcinoma in 45%, oncocyte differentiation in 3 patients and trabecular differentiation in one patient. Two patients had a non-invasive follicular thyroid tumor with papillary nuclei (NIFTP). Tumor foci were found in the 2 thyroid lobes in 62% of cases. Lymph node invasion was found in 9% of cases, 2% of subjects had distant metastases. Complete remission was noted in 65% of patients, a biologically incomplete response in 6%, and morphologically incomplete response in 10% of cases. Bivariate analysis of the factors influencing the occurrence of locoregional or distant metastasis showed a statistically significant difference in the case of male sex (P=0.009) and vascular invasion on the pathological study (P <0.001).

Discussion: In our present study, multifocality was unrelated to an increase in the aggressiveness of differentiated thyroid carcinomas. However, a study with a larger follow-up would be interesting to evaluate the long-term prognosis of these so-called tumors.