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We read with interest the article of Gorenberg et al [1] entitled "Patterns of FDG uptake in post-thoracomy surgical scars in patients with lung cancer". Here, we present two cases of abdominal/pelvis incisional scar activity within 2 weeks and 4 weeks after surgery; the scar activity completely disapeared at 5 months in one case. We completely agree with their conclusion that "Benign F-18 FDG activity in surgical scars is mainly diffuse and decreased activity with time, with 60% of studies showing no abnormal scar uptake >12 months after surgery". Post-surgical changes are a frequent cause of artefacts on fluorodeoxyglucose–positron emission tomography (FDG–PET) imaging. Surgery is a form of tissue injury and it elicits an inflammatory response, which can be visualised as an area of focal increased FDG activity. These changes usually resolve in a few weeks and a PET scan in such cases is, therefore, recommended 6–8 weeks after surgery to avoid post-surgical changes interfering with scan interpretation [2, 3]. A laparoscopic scar mimics a nodule on PET/CT [4]. We emphasise the value of knowledge of the patient history and an awareness of the different pitfalls of FDG uptake to achieve a correct diagnosis with FDG–PET.
Case 1
Case 1 was a 56-year-old man with a history of anaemia and syncope. The episode was evaluated by endoscopic examination, which showed perforation of the stomach along the greater curvature into the gastrosplenic ligament. An exploratory laparotomy was performed with a midline laparotomy in the supraumbilical position. Perforation of the greater curvature gastric ulcer and splenic abscess were found; partial gastrectomy and splenectomy were performed. Pathologically, large cell B-cell lymphomas were found in the spleen and gastric ulcer. 2 weeks after the surgery, the patient underwent FDG–PET, which showed a linear increase in FDG uptake in the midline of the abdomen below the diaphragm and multiple irregular activity in the left posterior abdomen owing to a post-surgical scar (Figure 1a
). The patient underwent six cycles of a combination of cyclopasphamide, doxorubicin, vincristine and prednisone (CHOP) chemotherapy. To monitor therapeutic response, the second and third FDG–PET scans were performed 5 months and 11 months, respectively, after the first FDG–PET; the second PET scans no longer showed linear activity in the midline scar (Figure 1b). The third FDG–PET scans showed no activity in the incisional scar (data not shown).
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Case 2 was a 60-year-old man with a retroperitoneal mass who had shown a gradual loss of weight of 50 lb over several years. He underwent an exploratory laparotomy with the en block resection of a large left retroperitoneal mass adherent to the spleen, left kidney, sigmoid colon and left adrenal gland by a midline skin incision from just below the xiphoid process to just above the pubic symphysis. The 20 lb mass was confirmed to be dedifferentiated liposarcoma with focal myoid features; the spleen, left kidney, sigmoid colon and adrenal gland were not involved. For restaging, the patient underwent FDG–PET scans 4 weeks after surgery and showed a midline incisional scar in the abdomen extending to the pelvis (the xiphoid process to the symphysis), which was broader in the distal third (Figure 2).
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The authors thank Mark Ingram, reference librarian, for his excellent and diligent search of the literature during the preparation of this Letter.
Yours etc.,
1 Department of Radiology, Weill Cornell Medical College, Cornell University, New York, 2 Nuclear Medicine Service, Lexington VA Medical Center and Department of Diagnostic Radiology, University of Kentucky Medical Center, Lexington, E-mail: wshih0{at}uky.edu, 3 Radiology Service, Lexington VA Medical, Lexington, USA
Received for publication February 27, 2009. Accepted for publication March 10, 2009.
References
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