Clinical Nuclear Medicine:
In the article by Dong et al on pages e98–e100 of the February 2013 issue, the figure captions were represented incorrectly. The corrected captions are as follows:
FIGURE 1. A 21-year-old woman was admitted to our hospital after incidental detection of a left renal lesion on ultrasound scan. Abdominal contrast-enhanced CT scan on the arterial (A) phase revealed a moderately enhanced lesion (2.8 × 2.0 cm) in the left kidney without fat density (arrow). FDG PET/CT was performed for whole-body survey. Blood glucose level on the day of PET/CT was 5.9 mM and a dose of 373 MBq (10.1 mCi) of FDG was injected intravenously. Sixty minutes after the FDG injection, CT and PET images of the skull to the upper thighs were consecutively acquired. The transverse CT image (C), corresponding PET image (B), and fusion image (D) showed increased FDG uptake of the left renal lesion (arrow; SUVmax, 4.4).
FIGURE 2. Abdominal contrast-enhanced CT scan on the arterial (A) phase revealed a well-demarcated round mass (3.3 × 3.3 cm) anterior to the right psoas major muscle, with slight enhancement (arrow). The transverse CT image (C), corresponding PET image (B), and fusion image (D) showed slightly increased FDG uptake of the mass (arrow; SUVmax, 2.9).
FIGURE 3. Excision of the left kidney and the retroperitoneal mass was performed. Histopathology at low [A; hematoxylin and eosin (H-E), ×40] and higher (C; H-E, ×100) magnification showed that the renal tumor was composed of round and polygonal epithelioid cells with clear cytoplasm. The nuclei of the tumor cells were mild bizarre in appearance. No fatty component was identified, and the proportion of the epithelioid cells was 100%. Immunohistochemically, the tumor cells showed strong HMB-45 cytoplasmic reaction (B; original magnification, ×100). These findings were consistent with pure epithelioid angiomyolipoma (EAML). Histopathology (D; H-E, ×40) of the retroperitoneal mass revealed areas of typical Antoni A and Antoni B with intense staining of S-100 protein, which were consistent with schwannoma. Renal AML is a mesenchymal neoplasm composed of variable proportions of dysmorphic blood vessels, smooth muscle, and adipose tissue.1 Epithelioid AML is a rare variant of atypical AML in which epithelioid component comprises more than 10% of the tumor. Only about 1% of renal AMLs show purely epithelioid morphology.1 Malignant behavior has been reported in renal EAMLs.2,3 Radiological features of EAML of the kidney are rarely reported to date. It is difficult to differentiate EAML from renal cell carcinoma on CT imaging because adipose tissue is usually absent in EAML.4–6 There are a few authors who reported PET findings of AMLs. Lipid-poor AMLs may mimic renal cell carcinoma on 18F-FDG PET because of increased FDG uptake.7,8 Dual-tracer PET scans reveal that renal AMLs present with increased 11C-acetate avidity and with no or slightly increased 18F-FDG uptake.9–11 To our knowledge, this case was the first report of FDG-avid pure EAML of the kidney. Retroperitoneal schwannomas are rare, comprising approximately 3% of all schwannomas.12,13 Previous reports show that schwannoma may mimic metastasis from an unknown or known primary cancer on FDG PET/CT.14,15 This case of retroperitoneal schwannoma was misdiagnosed as a metastasis because the left renal tumor of high FDG uptake mimicked renal cell carcinoma.
Dong A, Wang Y, Zuo C. Synchronous pure epithelioid angiomyolipoma of the kidney and retroperitoneal schwannoma in the same patient on 18F-FDG PET/CT imaging. Clin Nuclear Med. 2013; 38: e98–e100.