[Renal cell carcinoma diagnosed by ring-like growth of preexistent calcification: a case report]

A 53-year-old woman was referred for further examination of a left renal cyst detected ultrasonographically during a health checkup. Computerized tomography (CT) scan and magnetic resonance imaging revealed an irregular cystic mass at the center of the left kidney as well as a calcified lesion at the left upper pole. Angiography and cyst puncture confirmed the cystic mass to be unilocular and benign. However, followup CT scan after 22 months demonstrated enlargement of the calcification into a ring-like configuration 3 cm in diameter. Since the lesion showed neovascularity on angiography, radical nephrectomy was performed. Histopathological diagnosis was renal cell carcinoma, alveolar type, common type at the center, but solid type, spindle cell type at the periphery.