LAUSR

A 79-year-old woman with recurrent invasive lobular carcinoma (ILC) of the right breast underwent right mastectomy with right axillary node dissection, radiotherapy at the right chest wall, and letrozole. She presented with progressive dysphagia and requested for positron emission tomography/ computed tomography (PET/CT) with [18F]-fluorodeoxyglucose (FDG) and [18F]-fluoroestradiol (FES). (a) Maximal intensity projection (MIP) images of [18F]-FDG (left) and [18F]-FES (right) revealed [18F]-FES-avid lesions in the mediastinal and right chest wall regions with low [18F]FDG. (b) Axial images showed non-[18F]-FDG-avid circumferential soft tissue thickening of the oesophagus but intense [18F]-FES avidity. (c) A [18F]-FDG-avid soft tissue mass at the right chest wall yielded more intense [18F]-FES avidity with (d) non-[18F]-FDG-avid soft tissue thickening at the right anterior and lateral chest wall showed intense [18F]-FES avidity, supporting ER-positive oesophageal and right chest wall metastases. EGD with biopsy confirmed metastatic ILC (ER 80%). Her treatment plan was changed to systemic therapy combined with palliative oesophageal radiotherapy. The oesophagus is a rare metastatic site of breast cancer with a prevalence of 4.2–5.9% [1]. [18F]-FES strongly correlates with oestrogen-receptor (ER) expression [2–4]. Thus, [18F]-FES can be a non-invasive evaluation of ER with comparable sensitivity to [18F]-FDG for tumour and metastasis detection [5]. Our results yielded a discrepancy between [18F]FDG and [18F]-FES findings with low [18F]-FDG accumulation in ILC from low tumour density, low GLUT-1 expression, low proliferation rate, and an infiltrative growth pattern [6]. In contrast, more than 95% of ILCs have positive ER [7]. Thus, [18F]-FES might be more helpful for ER-positive ILC.