Clinical and prognostic characteristics of poorly differentiated thyroid carcinomas

Background. Poorly differentiated thyroid cancer (РDTC) is a rare, invasive, highly malignant carcinoma originating from follicular cells that histologically has a solid, trabecular, and insular growth pattern (or their combinations). At the beginning of the 21st century, poorly differentiated carcinoma was recognized as a separate entity and histological criteria for its diagnosis were established. Despite efforts to study poorly differentiated carcinomas, they still pose a significant challenge to clinicians due to the difficulties associated with the diagnosis, urgent need for complex thyroidectomy, high recurrence rate, and significant lethality from non-anaplastic thyroid cancer. The purpose of the study: a retrospective analysis of clinical data of patients with РDTC regarding preoperative diagnosis, tumor characteristics, effectiveness of treatment strategies, factors that may affect the duration of the postoperative period and survival rate. Materials and methods. A retrospective analysis of data from 23 patients with PDTC who were examined and operated over a 20-year period was conducted. We analyzed the age, gender of the patients, tumor size and classification according to the TNM system, results of cytological studies of aspirates (fine needle aspiration biopsy), presence of invasion (into the capsule, blood and/or lymphatic vessels of the tumor, intra- or extrathyroidal), extent of surgical intervention, postoperative treatment, health status (patients in remission, prolongatio morbi, died), duration of postoperative life and cumulative survival. Results. The age of most patients with PDTC was over 50 years; the ratio of women to men was equal. There is no gender difference in the main clinical characteristics of the disease, except for larger tumor size in male patients and a higher risk of invasive carcinomas in them. Analysis of the results of cytological studies of aspirates showed their low diagnostic value in cases of PDTC: carcinoma was not correctly diagnosed in any case, and 38 % of tumors were classified as Bethesda II–IV. 87 % of patients had T3-T4 carcinomas, 78 % exceeded 4 cm in size, more than half of them were widely invasive; among metastatic tumors, 75 % had metastases to the lateral cervical lymph nodes, and cases of compression of structures surrounding the thyroid were also observed. Such unfavorable clinicopathological characteristics caused high mortality (60.9 %), short lifetime after surgery (from 5 to 84 months, average of 17.7 months) and low survival rate during the first 5 postoperative years (22.5 %). It was noted that most deaths occurred in the first 3 postoperative years, with the number/percentage of deaths decreasing with time after carcinoma removal. Conclusions. The diagnostic value of fine needle aspiration biopsy results in the preoperative diagnosis of PDTC is low. The data obtained allow us to recommend mandatory surgery in patients aged 60+ with a Bethesda III–IV diagnosis. Tumor invasion within the thyroid gland, presence of metastases in cervical lymph nodes, and absence of postoperative radiation therapy may be risk factors for death in the first years after surgery, while patient age, tumor size, and extrathyroidal invasion are the main prognostic biological markers of survival in patients with poorly differentiated thyroid cancer.