Isolated omental metastasis of renal cell carcinoma after extraperitoneal open partial nephrectomy: A case report

Abstract

Introduction: Metachronous metastatic spread of clinically localized renal cell carcinoma (RCC) affects almost 1/3 of the patients. They occur most frequently in lung, liver, bone and brain. Isolated omental metastasis of RCC has not been reported so far.

Case presentation: A 62-year-old patient previously diagnosed and treated due to pulmonary sarcoidosis has developed an omental metastatic lesion 13 years after having undergone open extraperitoneal partial nephrectomy for T1 clear-cell RCC. Constitutional symptoms and imaging findings that were attributed to the presence of a sarcomatoid paraneoplastic syndrome triggered by the development this metastatic focus complicated the diagnostic work-up. Biopsy of the [18F]-fluorodeoxyglucose (+) lesions confirmed the diagnosis of metastatic RCC and the patient was managed by the resection of the omental mass via near-total omentectomy followed by targeted therapy with a tyrosine kinase inhibitor.

Discussion: Late recurrence of RCC has been reported to occur in 10-20% of the patients within 20 years. Therefore lifelong follow up of RCC has been advocated by some authors. Diffuse peritoneal metastases have been reported in certain RCC subtypes with adverse histopathological features. However, isolated omental metastasis without any sign of peritoneal involvement is an extremely rare condition.

Conclusion: To our knowledge, this is the first reported case of metachronously developed, isolated omental metastasis of an initially T1 clear-cell RCC. Constitutional symptoms, despite a long interval since nephrectomy, should raise the possibility of a paraneoplastic syndrome being associated with metastatic RCC. Morphological and molecular imaging studies together with histopathological documentation will be diagnostic.

Keywords: Case report; Metastasis; Omentum; Renal cell carcinoma.

Fig. 1

Sagittal fat saturated T2-weighted magnetic resonance image. A round, well-circumscribed, T2-heterogeneous signal intensity mass (arrow) displaces the anteroinferior urinary bladder inferiorly.

Fig. 2

[18F]-Fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) (A) Maximum intensity projection (MIP) image shows innumerable hypermetabolic foci throughout the lungs, osseous structures, and lymph nodes above and below the diaphragm. (B) CT soft tissue window, Fusion PET-CT, and CT bone window images show the index supravesical lesion with faint FDG uptake (thick arrow). Focal hypermetabolic right iliac bone lesion was also targeted for biopsy revealing sarcomatoid reaction (thin arrow).

Fig. 3

(A) Histopathology of the suprapubic mass demonstrate a neoplasm composed of cells with clear vacuolated cytoplasm and hyperchromatic small nuclei (H&E, ×90). (B) Immunohistochemically, tumor cells show nuclear positivity with PAX8 (IHC stain ×150). (C) Immunohistochemically, tumor cells show strong, diffuse positivity with CD10 (IHC stain ×150). (D) H&E stained sections of the neddle biopsy from the iliac bone showing granulomatous inflammation (×150).

Fig. 4

Macroscopic appearance of the omental metastatic deposit. Note its prominent vascular supply and collateral vascular network covering its surface.

Fig. 5

Omental tumor has similar histopathologic features with the suprapubic mass, consistent with clear cell renal cell carcinoma (H&E ×30).