Invasiveness and Metastatic Aggressiveness in Small Differentiated Thyroid Cancers: Demography of Small Papillary Thyroid Carcinomas in the Swedish Population

Abstract

Background The western world is seeing a rising incidence of thyroid cancer. Improved diagnostic methods do not entirely explain this increase. Papillary thyroid carcinoma (PTC) is the most common subtype of thyroid cancer. Small PTC (B20 mm) and especially papillary thyroid microcarcinomas (PTMC B10 mm) are considered to be lowrisk tumors but some cases are considerably more aggressive. Sufficient understanding of these mechanisms is a long-term goal for more efficient and safer treatment of these tumors. Methods We identified 959 cases of small PTCs in the validated Scandinavian Quality Register for Thyroid, Parathyroid and Adrenal Surgery, grouped according to lymph node metastasis. These were analyzed according to age, gender, tumor size and geographic region. Results Patients with N1b disease (lateral lymph nodes metastases) had a smaller tumor size compared to patients with N1a disease (8.6 mm vs 10.1 mm respectively, p \ 0.05). Patients and specifically females with N1b disease were younger than those with N0 or N1a disease. Patients with N1b disease had a lower proportion of females (60%) compared to N0 and N1a groups (81% and 78%, respectively). The incidence of operated small PTCs and of lymph node engagement differs between geographic regions in Sweden.Conclusions Small PTC and especially PTMC seem to show different patterns of aggressiveness and demography regarding lateral lymph node metastases and 7% had N1b disease and tumor \1 cm, underscoring the importance of lymph node evaluation in PTMC patients. More understanding of predictive factors, mechanisms for metastatic disease and causes of regional differences, is needed.

Risk factors for recurrent disease in small papillary thyroid cancers – a Swedish register-based study

“…The results support the hypothesis that recurrence rate, rather than mortality rate, is a preferable clinical measure when discussing sPTC. Given the difference regarding intervention-requiring cancer recurrence between N1b and N1a/N0, LN status plays an important role in individual risk stratification, and this emphasizes the need for thorough preoperative LN mapping even in sPTC [ 8 ]. Central lymph node metastasis (CLNM) has been shown to be the strongest risk factor for lateral lymph node metastasis.…”

“…Due to the good prognosis, the general approach is towards less aggressive management of these small tumours [ 4 ]. Although most sPTCs are considered low risk cancers, some are considerably more aggressive than others with a high recurrence risk [ 2 , 5 – 8 ].…”

The correlation between small papillary thyroid cancers and gamma radionuclides Cs-137, Th-232, U-238 and K-40 using spatially-explicit, register-based methods

“…Unexplained regional differences in the distribution and increase of sPTC have been listed in Sweden (32). Early detection of more aggressive forms of thyroid cancer is essential for proper surgical and oncological treatment of these patients.…”

“…This method is innovative and could draw attention to as yet unknown factors influencing thyroid cancer, and may potentially prove useful within other fields of medical research. Unexplained regional differences in the distribution and increase of sPTC have been listed in Sweden (32). Early detection of more aggressive forms of thyroid cancer is essential for proper surgical and oncological treatment of these patients.…”

Combination of ultrasound with BRAF V600E gene detection for the evaluation of aggressive behavior of papillary thyroid microcarcinoma

“…Nearly 50% of thyroid cancer cases consist of PTC measuring 10 mm or less in size (papillary thyroid microcarcinoma [PTMC]) (2) . It has been reported that although the clinical outcome of patients with PTMC (usually considered to be an indolent tumor) is excellent, there are still a considerable number of cases related to poor prognoses, such as capsule invasion (3)(4)(5) . Based on the excellent prognosis of patients with PTMC, Kuma Hospital and Cancer Institute Hospital of the Japanese Foundation for Cancer Research first proposed the concept of indolent PTMC (cancer foci without lymph node metastasis, extrathyroidal extension [ETE], or distant metastasis) and aggressive PTMC (cancer foci with lymph node metastasis, ETE, or distant metastasis) and began a study of active surveillance for indolent PTMC instead of surgical treatment (6) .…”