FDG-PET/CT finding of benign metastasizing leiomyoma of the lung
A 50-year-old woman with a history of hysterectomy for uterine leiomyoma 12 years ago was examined for multiple small lung nodules, including the largest one (30 × 25 mm in size) which were incidentally discovered on chest radiographs at a private hospital (Fig. ). Unenhanced CT images showed multiple peripheral parenchymal nodules of variable sizes with smooth margins (Fig. ).\nFDG-PET was performed using a PET/CT system (GE Discovery STE, GE Healthcare, Milwaukee, WI, USA) to identify primary malignancy and metastatic lesions. A whole-body imaging from the head to the thigh and chest imaging were performed 1 hour (early) and 2 hours (delayed), respectively, after intravenous injection of FDG (3.7 MBq/kg body weight). At PET/CT, her blood glucose level was 93 mg/dl. Faint FDG uptake was noted in the largest nodule (Fig. a and b), and its early and delayed maximum standardized uptake values (SUVmaxs) were 1.3 and 1.2, respectively. In this connection, early and delayed SUVmaxs were 0.5 and 0.5 in the lung field, 1.5 and 1.4 in the thoracic muscle, and 2.4 and 1.6 in the mediastinum at the Fig. a tomographic level, respectively. The remaining smaller nodules ≤ 8 × 8 mm in diameter showed no visible uptake (early SUVmax 0.5–0.8; delayed SUVmax 0.4–0.6) (Fig. c and d). There was no other pathologic FDG uptake to suspect primary malignancy and metastatic lesions in the whole body.\nCT-guided needle lung biopsy was performed for the largest nodule to obtain a pathological diagnosis of the lung nodules. Microscopic examinations showed an interlacing pattern by spindle cells having elongated nuclei without cellular atypia (Fig. a). The Ki67 proliferative index was less than 1%. Tumor cells were positive for alpha-smooth muscle actin (Fig. b) and both estrogen and progesterone receptors and negative for CD31, CD34, AE1/AE3, EMA, HMB45, and S-100 protein on immunohistochemical stains. The pathological findings of the tumor confirmed the diagnosis of benign metastasizing leiomyoma. The patient selected careful observation as a management and the chest radiographs showed no change to date, 1 year after the biopsy.