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Minerva Chirurgica 2007 October;62(5):315-25


language: Italian

Papillary thyroid microcarcinoma. Long-term outcome in 587 cases compared with published data

Pelizzo M. R. 1, Merante Boschin I. 1, Toniato A. 1, Piotto A. 1, Bernante P. 1, Pagetta C. 1, Casal Ide E. 1, Mazzarotto R. 2, Casara D. 2, Rubello D. 3

1 Divisione di Patologia Speciale Chirurgica Dipartimento di Scienze Mediche e Chirurgiche Università di Padova Istituto Oncologico Veneto (IOV)-IRCCS Padova 2 Divisione di Medicina Nucleare Dipartimento di Radioterapia Istituto Oncologico Veneto (IOV)-IRCCS Padova 3 Divisione di Medicina Nucleare, Unità PET Ospedale S. Maria della Misericordia’ Istituto Oncologico Veneto (IOV)-IRCCS Rovigo


Aim. Papillary thyroid microcarcinoma (PTMC), a tumor measuring ≤1 cm according to the World Health Organization (WHO) histologic classification, is the most common histologic variant of thyroid cancer. The aim of this study was to evaluate the long-term outcome of surgical treatment for PTMC at a single institution with a view to differentiate therapy options based on risk of progression of disease by comparing our results with those reported in the literature.
Methods. The study sample was a total of 587 cases of PTMC treated surgically at our institution between 1990 and 2006. PTMC was an incidental finding (PTMC-I) in 325 (55.4%) cases, diagnosed preoperatively (PTMC-D) at echography and needle-aspiration biopsy in 229 (39%), and occult with metastasis (PTMC-O) in 33 (5.6%). Patients were grouped into two classes (PTMC diameter ≥5 mm or <5 mm) and compared against prognostic factors: sex, age, type of PTMC (PTMC-I, PTMC-D, PTMC-O), extent of surgery, lymph node dissection, lymph node metastasis, iodine-131 (131-I) therapy, state of disease, relapses. These parameters were then compared against tumor size (PTMC diameter ≥5 mm or <5 mm), excluding cases of PTMC-O with metastasis.
Results. Comparison of the two groups divided by tumor size, across the entire sample and after PTMC-O cases were excluded, revealed significant differences in the type of PTMC, frequency of partial thyroidectomy, presence of lymph node metastasis, iodine-131 therapy, life status and recurrence rate.
Conclusion. Published PTMC studies were analyzed for definition of the disease, incidence, therapy, prognosis, and follow-up results and compared with our data. The results of our analysis argue against use of the term “microcarcinoma” in the wider sense since the three PTMC categories (PTMC-I, PTMC-D, PTMC-O) present different behaviour patterns. When cases of PTMC-O with clinically manifest metastasis were excluded, none of the patients with PTMC <5 mm in diameter were reoperated for tumor recurrence and all are currently free of disease. In conclusion In PTMC <5 mm in diameter, whether PTMC-I and PTMC-D, and without evidence of lymph node involvement, partial thyroidectomy may be a viable approach to treatment. By contrast, occult PTMC with metastasis is prognostically important and should therefore be treated like tumors ≥5 mm in diameter.

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