The clinical course of poorly differentiated thyroid carcinoma (insular carcinoma) - own observations

Poorly differentiated thyroid carcinoma (PDTC, insular carcinoma) occurs rarely. It is described with more aggressive behaviour, poorer prognosis, and higher mortality than well differentiated thyroid carcinoma (WDTC). The aim of this study was to evaluate the clinical course of patients with PDTC, in addition to frequency, clinical stage at the time of diagnosis and the possibility of radical surgical resection, the necessity and kind of complementary treatment, occurrence of distant metastases, and the survival of patients.

The study involved 14 patients (9 females, 5 males) diagnosed and treated for PDTC between 2000 and 2009, aged 38 to 78 years. The medical records of patients with PDTC were analyzed to estimate assumed parameters according to the purpose of the study.

PDTC was diagnosed in 14 among 801 patients with thyroid carcinoma (1.75%). Clinical stages (UICC 2002) at the time of diagnosis were as follows: 3 patients - pT(₁-₂)N(o-x)M(x) (21.5%); 10 patients - pT(₃ ₄)N(x o ₁)M(x-₁)(71.4%); and 1 was unresectable - T(x)N₁M₁ (7.1%). Total thyroidectomy was achieved in 9 patients (64.3%), and 4 patients (28.6%) received non radical surgery. Complementary radioiodine treatment was given to 12 patients (85.8%). Radiation therapy of the neck was applied to 7 patients, palliative radiotherapy of the brain to 1 patient, and chemotherapy to 1 patient. Distant metastases to the lung and to the brain at diagnosis were observed in 2 patients (14.3%). During follow-up of 3-62 months lung metastases were observed in 4 patients (28.6%), three patients were observed above 5 years as disease-recurrence free (21.5%), but in one patient after 5 years and 2 months distant metastases were diagnosed. Three patients died after 2-30 months (21.5%), 2 patients were lost for control, and in the remaining 6 follow-up lasted for less than 5 years.

Poorly differentiated thyroid carcinoma is still a challenge both for pathologists and clinicians. Infrequent prevalence, more aggressive course, and poorer prognosis constitute major problems for the clinicians.