Urothelial carcinoma mimicking Bosniak IV cystic mass: A case report

Abstract

Urothelial carcinoma is the primary malignancy of the urothelium that has varying radiographic features based on the location of the tumor. Differentiating urothelial carcinoma from renal cell carcinoma is critical as interventions and management methods differ. We present a case of urothelial carcinoma within the calyceal diverticula that was initially suspected to represent Bosniak IV cyst due to cystic renal cell carcinoma. A 71-year-old male with a history of gross hematuria and a previously identified Bosniak II renal cyst underwent further imaging, revealing a Bosniak IV cystic mass with enhancing nodules. Subsequent nephrectomy unveiled noninvasive low-grade papillary urothelial carcinoma within a calyceal diverticulum. This case highlights the complexity of diagnosing urothelial carcinoma within the calyceal diverticula, emphasizing the need for a high index of suspicion. The study contributes to understanding the limitations of imaging modalities, especially in cases involving calcification or stone evaluation. The coexistence of urothelial carcinoma and calyceal diverticula is rare but crucial for accurate diagnosis and treatment. Documenting cases like these is vital for recognizing urothelial carcinoma mimics and ensuring appropriate patient management. The study underscores the significance of distinguishing features of calyceal diverticula and advocates for comprehensive imaging approaches in renal cystic lesions.

Keywords: Calculi; Case reports; Cystic kidney diseases; Cysts; Diverticulum; Kidney; Kidney neoplasms; Renal cell carcinoma; Transitional cell carcinoma.

Fig. 1

MRI of the right kidney. (A) T2 axial MRI shows hyperintense diverticulum (dotted lines) with hypointense layering calcifications/calculi (white arrowheads) (B) Contrast enhanced axial T1 image show enhancing nodules (white arrows) and contrast excretion into the renal pelvis (white *).

Fig. 2

CT of the right kidney. (A) Noncontrast axial CT shows a cystic lesion with a few layering calcifications/calculi (white arrowheads). (B and C) contrast enhanced axial and coronal images show a peripheral rim of enhancing soft tissue material (white arrows) in the cystic lesion (dotted lines). (D) Delayed excretory phase coronal post contrast CT shows contrast excretion into the renal pelvis (black *) and not within the cystic lesion (dotted line).

Fig. 3

(A) Histologic examination shows fused to branching fibrovascular cores lines by neoplastic urothelium. From low power, architecture is relatively organized and cytology appears uniform, supporting a low-grade lesion. There is no invasion past the basement membrane. (B) From high power, there is slight variation in size and shape of nuclei, but in general polarity is maintained. Mitoses are rare. These features support the diagnosis of low-grade papillary urothelial carcinoma. (C) Macroscopic surgical specimen of urothelial carcinoma (dotted lines) with layering calcifications (white arrowhead).