Insights into the Management of Papillary Microcarcinoma of the Thyroid

Abstract

Background: Rapid increases in the incidence of thyroid carcinoma with stable mortality rates from thyroid carcinoma have been reported from many countries, and these increases are thought to be due mostly to the increased detection of small papillary thyroid carcinomas (PTCs), including papillary microcarcinomas (PMCs; i.e., PTCs ≤10 mm). Some researchers have suggested that small PTCs have been overdiagnosed and overtreated. In Japan, the active surveillance of patients with low-risk PMCs was initiated by Kuma Hospital (1993) and Tokyo's Cancer Institute Hospital (1995) based on the extremely higher incidences of both latent thyroid carcinomas in autopsy studies and small PTCs detected in mass screening studies using ultrasound examinations compared to the prevalence of clinical thyroid carcinomas.Methods: The above two institutions' data are summarized regarding the active surveillance of low-risk PMCs, and future prospects for their management are discussed.Results: At 10-year observations in the Kuma Hospital series of 1235 patients, only 8% and 3.8% of the PMC patients showed size enlargement by ≥3 mm and the novel appearance of node metastasis, respectively. In contrast to clinical PTC, PMCs are most unlikely to grow in older patients (≥60 years). In the Kuma Hospital series, the 974 patients who underwent immediate surgery had significantly higher incidences of unfavorable events than the 1179 patients who chose active surveillance. The total cost of immediate surgery, including the costs for salvage surgery and postoperative care for 10 years, was 4.1 times the total cost of 10-year management by active surveillance. Only 8% of the 51 PMC patients showed tumor enlargement during pregnancy, and the rescue surgeries after delivery were successful. In the Cancer Institute Hospital series of 230 patients with 300 lesions, only 7% and 1% of the patients showed size enlargement and novel node metastasis, respectively, and that institution's analysis also revealed that macroscopic or rim calcification and poor vascularity were correlated with non-progressing disease. In both series, none of the patients who underwent rescue surgery after progression signs were detected showed significant recurrence or died of PTC.Conclusion: Active surveillance of low-risk PMC can be the first-line management. Interestingly, older patients with low-risk PMCs are the best candidates for active surveillance.

Low‐risk papillary thyroid microcarcinoma: Optimal management toward a more conservative approach

“…Suspicious lymph nodes should undergo fine‐needle aspiration cytology and thyroglobulin measurement in the needle wash‐out 25 to confirm lymph node metastasis. In this case, total thyroidectomy with therapeutic lymph node dissection is performed 11 …”

“…The large difference between the incidence of microPTC in autopsy series (occult tumors) and screening studies, and the prevalence of clinical thyroid carcinoma indicate that most of these tumors remain small, clinically silent, and indolent over time, whereas only small subgroup progress. For this reason, delayed surgery after the detection of progression in terms of tumor growth or node metastasis is still feasible 11 . Nevertheless, the minority of cases with a more aggressive phenotype (lymph node and distant metastasis at the time of diagnosis or during early postoperative follow‐up) still require a better understanding of the natural history of these tumors and their optimal management strategy 12 .…”

The new 4th edition World Health Organization classification for thyroid tumors, Asian perspectives

“…Comprehensive risk stratification of PMC considers a constellation of clinical, pathological, and molecular parameters . Observation without surgical treatment is practiced for patients with low‐risk PMC in several leading medical centers in Japan, Korea and the USA . Less than 15% of low‐risk PMC grow to more than 3 mm or develop lymph node metastasis during follow‐up, and most importantly, no thyroid cancer death was reported among more than 1000 patients for more than 10 years of follow‐up .…”

Understanding the natural history of papillary thyroid cancer: Case series

“…The other patient that underwent surgery alone did so in our study. Ito and colleagues followed 1225 patients in Japan with papillary microcarcinomas (<1 cm) and found a 4.6% rate of tumor enlargement (>3 mm) over a follow‐up period of 10 years …”

“…However, their study did not include data on overall or disease‐specific survival . Unlike United States‐based studies with typically shorter periods of active surveillance, studies from Japan outline a follow‐up of approximately 10 years under an active surveillance protocol …”