FDG-PET imaging in patients with pulmonary carcinoid tumor

This study aimed to assess the imaging findings in patients with pathologically proven carcinoid tumors and determine if SUV can help to differentiate typical from atypical (more aggressive) pulmonary carcinoid tumors.

A retrospective review of patients with a biopsy-proven diagnosis of a pulmonary carcinoid tumor at our institution from 2002 to 2010 that had a preoperative PET scan was performed after institutional review board approval was obtained. PET results, including SUV uptake and location, were recorded as well as all data from pathology reports. Carcinoids were considered to be more aggressive if they showed pathological diagnosis consistent with atypical carcinoid, lymph node invasion, poor histological grade (poorly differentiated), or evidence of systemic metastases. Atypical carcinoid pathology consisted of focal necrosis or a higher mitotic index (2-10 per square millimeter) with features of nests, trabeculae, pleomorphic cells, or dense hyperchromasia. SUV uptake was then evaluated and compared between the typical and atypical carcinoid groups using nonparametric statistical methods.

We identified 29 patients from 2002 to 2010 at our institution with a pathological diagnosis of pulmonary carcinoid. Twenty-three were histopathologically typical, and the other 6 showed atypia. Mean (SD) nodule size was 2.4 (1.3) cm in the typical group versus 5.0 (3.2) cm in the atypical group (P = 0.065). Mean (SD) SUV uptake in the typical carcinoid group was 2.7 (1.6) and in the atypical group the SUV was 8.1 (4.1) (P < 0.01). A cutoff SUV of 6 or greater is predictive of malignancy (odds ratio, 23.6; P < 0.01), as well as a nodule size of 3.5 cm or greater (odds ratio, 5.1; P = 0.024).

Preoperative PET imaging result is frequently positive in carcinoid tumors, and the biological behavior correlates well with SUV; however, size is not as strong of a predictor of malignancy. Size of 3.5 cm or greater and SUV of 6 or greater have a predictive value of greater than 95% for malignant histology.