A rare case of a cystic renal mass with heterotopic ossification and a mini literature review.

Introduction: It is a challenge to make accurate pre-surgical diagnosis for renal tumors. This study is to report the findings, management, and outcome of one rare case of ossification in a cystic renal mass. We present and discuss the pathological characteristics, radiologic features, and treatment alternatives of the patient.

Patients And Methods: A 38 years old female patient had intermittent epigastric pain and microscopic hematuria for two months. Computerized tomography (CT) scan and Magnetic Resonance imaging (MRI) showed a mass with rough edge and dense calcification in the upper pole of the right kidney and normal left kidney. Pre-operative diagnosis is cystic nephroma or cystic renal mass (Bosniak III type, Bosniak renal cyst classification). GFR was within normal limits for age and no other significant laboratory aberrations were noted. Patient underwent a right retroperitoneal laparoscopic partial nephrectomy (margin status was negative). A mini literature review was performed to highlight the principals of diagnosis and treatment of cystic renal mass with heterotopic ossification.

Results: The entire renal mass was successfully removed from upper pole of the right kidney by laparoscopic nephron sparing surgery. The size of renal mass is 38×35×30 mm3 with thick and hard capsular wall. The cystic cavity contains yellow lipid-like substances without stone. Histological examination revealed renal cyst in which the cyst wall reveals fibrosis and no obvious lining epithelium. The additional unique feature includes the presence of dense calcification and ossification in the renal mass. Localization tissue of yellow bone marrow was detected. No complications occurred in 9 months after surgery during follow-up.

Conclusions: Cystic renal mass with heterotopic ossification is a rare case of non-malignant renal tumor. Whether surgery is needed depends to whether patients have symptoms. For symptom renal tumors, laparoscopic nephron sparing surgical procedure is recommended. Furthermore, complete surgical resection of the lesion is needed when the mass is suspected to be malignant. An accurate histologic diagnosis is key in its diagnosis.