Background The behavior of gastrointestinal stromal tumors varies according to tumor size, location, mitotic rate, and rupture. Traditional mitotic counting in 50 high-power fields (HPF; 5.3 mm2) may overestimate progression risk, as 5 mm2 corresponds to 20–25 HPF under modern microscopy. However, the 50-HPF method remains widely used. This study evaluated the impact of two mitotic counting methods on risk classification and developed a prognostic model combining inflammatory biomarkers with clinicopathological factors. Methods: We retrospectively analyzed 150 patients who underwent resection at Songklanagarind Hospital between 2009 and 2021. Patients who had received neoadjuvant therapy or had a second primary cancer were excluded. Mitosis was evaluated using both methods. Clinicopathological and serum biomarker data were collected. The primary outcome was 5-year disease-free or progression-free survival. The model was developed using forward stepwise variable selection based on the time-dependent area under the curve and internally validated by bootstrapping. Results: The 50-HPF method overestimated the Armed Forces Institute of Pathology classification in 14.2% of cases. A model incorporating tumor size, location, rupture, mitotic count within 5 mm2, and systemic immune-inflammation index achieved the highest area under the curve of 0.939 in both training and validation sets, outperforming previous models. The 5-mm2 method demonstrated superior performance to the 50-HPF method across all models (0.939 vs. 0.919 for the proposed model). Conclusions: Mitotic counting in 50 HPF overestimated risk classification in certain cases. Incorporating systemic immune-inflammation index and using a 5 mm2 mitotic count enhanced prognostic model performance.
Papillary thyroid carcinoma (PTC) is the most common thyroid malignancy, characterized by a range of subtypes that differ in their cytologic features, clinical behavior, and prognosis. Accurate cytologic evaluation of PTC using fine-needle aspiration is essential but can be challenging due to the morphologic diversity among subtypes. This review focuses on the distinct cytologic characteristics of various PTC subtypes, including the classic type, follicular variant, tall cell, columnar cell, hobnail, diffuse sclerosing, Warthin-like, solid/trabecular, and oncocytic PTCs. Each subtype demonstrates unique nuclear features, architectural patterns, and background elements essential for diagnosis and differentiation from other thyroid lesions. Recognizing these distinct cytologic patterns is essential for identifying aggressive subtypes like tall cell, hobnail, and columnar cell PTCs, which have a higher risk of recurrence, metastasis, and poorer clinical outcomes. Additionally, rare subtypes such as diffuse sclerosing and Warthin-like PTCs present unique cytologic profiles that must be carefully interpreted to avoid diagnostic errors. The review also highlights the cytologic indicators of lymph node metastasis and high-grade features, such as differentiated high-grade thyroid carcinoma. The integration of molecular testing can further refine subtype diagnosis by identifying specific genetic mutations. A thorough understanding of these subtype-specific cytologic features and molecular profiles is vital for accurate diagnosis, risk stratification, and personalized management of PTC patients. Future improvements in diagnostic techniques and standardization are needed to enhance cytologic evaluation and clinical decision-making in thyroid cancer.
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