INTERESTING IMAGE

Clear Cell Adenocarcinoma of the Urethra 18

F-FDG PET/CT Imaging Ba D. Nguyen, MD

Abstract: Clear cell adenocarcinoma of the urethra is a rare and aggressive tumor of female gender preponderance. This neoplasm, the origin of which is still widely debated, has been reported with CT and MRI in case reports and small series. To the previously published conventional cross-sectional imaging description, the authors add the PET/CT features of this uncommon urologic neoplasm at its advanced stage in a 60-year-old patient complaining of urinary retention. Key Words: clear cell adenocarcinoma, urethra, CT, MRI, PET (Clin Nucl Med 2015;40: 241Y243)

Received for publication March 18, 2014; revision accepted June 24, 2014. From the Department of Radiology, Mayo Clinic, Scottsdale, AZ. Conflicts of interest and sources of funding: none declared. Reprints: Ba D. Nguyen, MD, Department of Radiology, Mayo Clinic, 13400 E Shea Blvd, Scottsdale, AZ 85259. E-mail: [email protected] Copyright * 2014 Wolters Kluwer Health, Inc. All rights reserved. ISSN: 0363-9762/15/4003Y0241

Clinical Nuclear Medicine

REFERENCES 1. Mehra R, Vats P, Kalyana-Sundaram S. Primary urethral clear-cell adenocarcinoma: comprehensive analysis by surgical pathology, cytopathology, and next-generation sequencing. Am J Pathol. 2014;184:584Y591. 2. Alexiev BA, Tavora F. Histology and immunohistochemistry of clear cell adenocarcinoma of the urethra: histogenesis and diagnostic problems. Virchows Arch. 2013;462:193Y201. 3. Oliva E, Young RH. Clear cell adenocarcinoma of the urethra: a clinicopathologic analysis of 19 cases. Mod Pathol. 1996;9:513Y520. 4. Davis R, Peterson AC, Lance R. Clear cell adenocarcinoma in a female urethral diverticulum. Urology. 2003;61:644viiY644viii. 5. Kawashima A, Sandler CM, Wasserman NF. Imaging of urethral disease: a pictorial review. Radiographics. 2004;24(suppl 1):S195YS216. 6. Surabhi VR, Menias CO, George V. Magnetic resonance imaging of female urethral and periurethral disorders. Radiol Clin North Am. 2013;51:941Y953. 7. Pope TL, Harrison RB, Clark RL. Bladder base impressions in women: ‘‘female prostate’’. AJR Am J Roentgenol. 1981;136:1105Y1108. 8. Morikawa K, Togashi K, Minami S. MR and CT appearance of urethral clear cell adenocarcinoma in a woman. J Comput Assist Tomogr. 1995;19:1001Y1003. 9. Takeuchi M, Matsuzaki K, Nishitani H. Clear cell adenocarcinoma of the female urethra: magnetic resonance imaging. J Comput Assist Tomogr. 2009; 33:142Y144. 10. Grigsby PW. Carcinoma of the urethra in women. Int J Radiat Oncol Biol Phys. 1998;41:535Y541.

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FIGURE 1. Composite image of the pelvis with MRI and CT on the top row and PET/CT on the bottom row. A 60-year-old woman presented with voiding difficulties. Initially, she had a negative cystoscopic and urologic examination and was treated symptomatically with intermittent catheterization based on the presumed diagnosis of urethral stricture. She came to our institution for consultation 6 months later with worsening of the urinary retention. A repeat urologic evaluation detected a urethral mass. MRI showed a large mass underneath the urinary bladder (curved arrow) associated with bone lesions of the left pubic rami, proximal right femur and coccyx, and left pelvic nodal disease (arrows). CT confirmed the lytic features of the involved bones seen on MRI. PET/CT demonstrated the hypermetabolic features of the urethral mass and associated osseous and nodal metastases. Subsequent tissue sampling of the urethral tumor and lytic left pubic bone reached the diagnosis of clear cell adenocarcinoma (CCA). The patient underwent the intramedullary rod fixation of the impending right proximal femoral pathologic fracture. She was also planned for future chemotherapy and radiation therapy due to the advanced stage of the disease.

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Clear Cell Adenocarcinoma of the Urethra

FIGURE 2. The anterior and lateral PET MIP images showed increased 18F-FDG uptake of the CCA of the urethra (curved arrow) and metastases at the left pelvic nodes, left pubic rami, coccyx, and proximal right femur (arrows). Clear cell adenocarcinoma is a subtype of the uncommon adenocarcinoma of the urethra, which accounts for 10% of urethral cancer, less frequent than squamous cell carcinoma and transitional cell carcinoma (70% and 20% of urethral neoplasms, respectively).1 Its origin and pathogenesis are still widely discussed arising from mesonephric remnants, paraurethral glands, urethral diverticulum, or from malignant degeneration of nephrogenic adenoma.1Y4 Clear cell adenocarcinoma occurs predominantly in female patients of fifth and sixth decades of life in the premenopausal or menopausal clinical setting.5,6 This urethral lesion may be asymptomatic at early stage or manifest with dysuria, hematuria, and dyspareunia at advanced stages due to mass effect and invasion of the surrounding anatomic structures. Previously reported CT and MRI features described a mass arising from the proximal urethra or encasing this entire structure with potential extension to the vagina and elevation of the floor of the urinary bladder reminiscent of enlarged prostate features in male patients.5Y9 The urethra may be intact and well depicted by MRI at early stages but could be distorted and obliterated by larger CCA as seen in this presentation.8,9 Based on the importance of tumor staging and histology of urethral cancer, functional imaging with PET/CT may provide a more accurate evaluation and posttherapeutic monitoring of this uncommon but aggressive tumor.10

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CT imaging.

Clear cell adenocarcinoma of the urethra is a rare and aggressive tumor of female gender preponderance. This neoplasm, the origin of which is still wi...
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