Evaluation of Pleural-Based Nodules in a 52-Year-Old Woman with a History of Metastatic Breast Cancer

Abstract

A52-y-ol d woman with a history of invasive ductal carcinoma had undergone right mastectomy, right axillary lymph node dissection, and breast reconstruction. Two of six axillary lymph nodes were positive for ductal carcinoma at surgery, and the patient was staged pT2 pN1a Mx. A one-month follow-up chest CT scan showed multiple left-sided pleural-based nodules suggestive of metastatic disease. PET/CT, which was performed to further characterize these nodules, did not demonstrate significant 18 F-FDG uptake within them or evidence of metastatic disease (Fig. 1). In the process of formulating a differential diagnosis for these nodules, it was discovered that, as a child, the patient had sustained an accidental gunshot wound. The possibility of thoracic splenosis was suggested, and a 99m Tc-labeled heat-denatured red blood cell (DRBC) scan was ordered to confirm the origin of these conspicuous pleural-based nodules.A blood sample was drawn into a vial containing anticoagulant (acid citrate dextrose) labeled with 370 MBq (10 mCi) of 99m Tc-pertechnetate and heat-denatured by submersion in a 49.5°C (60.5°C) water bath for 20 min. Standard quality control analyses were completed. The radiolabeled autologous DRBCs were reinjected intravenously. Planar anterior and posterior images of the chest and abdomen were obtained 30 min after radiolabeled DRBC reinjection. Congruent SPECT and CT images of the chest and abdomen were also acquired and were displayed with and without fusion. QUESTION 1Localization of DRBCs takes place by what mechanism? A. Active transport by splenocytes via the adenosine triphosphatase-driven Na-K pump. B. Binding to transferrins, which localize to splenic tissue. C. Ion exchange on the cell membrane of splenocytes. D. Phagocytosis of the DRBCs by the reticuloendothelial system and size-and shape-dependent sequestration by the spleen.