However it has been shown that there is a significant number of false positivity (due to inflammatory diseases) and false negativity (due to low-grade malignancies) in the evaluation of primary tumor. The maximum standardized uptake value (SUVmax) greater than 2.5 is often used as a cut off value for malignancy. Elevated FDG uptake suggests that the lesions or tissues harbor tumor cells. The rationale for using FDG-PET in oncology is its ability to measure increased glucose metabolism of tumor cells. It also provides prognostic information, monitors response to therapy and can be used to follow up patients after treatment. The integration of PET with computed tomography (PET/CT) provides an accurate anatomic localization and improved staging especially for mediastinal lymph nodes and occult distant metastases. 2-fluoro-deoxy-D-glucose (FDG)-positron emission tomography (PET) is a metabolic imaging technique which has become an essential tool for staging of NSCLC patients. Histological classification and staging are critical in constituting a treatment strategy and predicting prognosis for NSCLC. Non-small cell lung cancer (NSCLC) is a heterogeneous group of carcinomas with different biological behaviors and prognoses. A T/LN SUVmax ratio lower than 5 predicts the metastasis to lymph nodes with a high sensitivity. SUVmax of a primary tumor is related to certain pathological characteristics, such as largest diameter, histology, and number of mitosis. A T/LN SUVmax ratio of 5 or lower was suggestive for a malignant lymph node with a sensitivity of 92.8% and specificity of 47%. The etiology of 100 PET/CT positive lymph node stations were metastasis in 14, anthracosis in 40, reactive in 39, granulomatous in 4, and silicosis in 3 patients. Patients with squamous cell carcinoma had a statistically significant higher mean SUVmax, number of mitosis and advanced N stages compared to adenocarcinoma. SUVmax of the primary tumor was positively correlated with the largest tumor diameter (p = 0.001, r = 0.374), number of mitosis (p < 0.001, r = 0.405), and postoperative pathological stage (p = 0.007, r = 0.298). A T/LN SUVmax ratio was calculated for each lymph node station. Pathological characteristics of the tumor such as largest tumor diameter, tumor histology, differentiation, number of mitosis, degree of stromal inflammation, necrosis etiology of PET/CT positive lymph node stations SUVmax of primary tumor and positive lymph node stations were recorded. There were 100 PET/CT positive mediastinal or hilar lymph node stations. MethodsĮighty-one NSCLC patients who had PET/CT examination at initial staging and subsequently underwent surgical resection were retrospectively evaluated. We aimed to investigate the correlation of maximum standardized uptake value (SUVmax) with pathological characteristics of primary tumor and to determine a Tumor/ Lymph node (T/LN) SUVmax ratio predicting metastasis to lymph nodes in NSCLC patients.
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