Incidental squamous cell carcinoma of renal pelvis presenting as skin invasion: a case report

INTRODUCTION: Squamous cell carcinoma of the renal pelvis is a rare neoplasm, accounting for less than 0.8% of malignant renal tumors. Chronic irritation is believed to be the primary pathogenic cause for squamous cell carcinoma of the renal pelvis. The most frequently reported cases of squamous cell carcinoma of the renal pelvis generally present with hydronephrosis, pyelonephritis, or nephrolithiasis. The skin of the flank is a very uncommon site of clinical presentation. Here, we report an exceedingly rare case of squamous cell carcinoma of the renal pelvis presenting as skin invasion of the flank. CASE PRESENTATION: A 66-year-old Han Chinese man consulted our hospital because of a right lumbar skin lesion lasting more than 3 months. His physical examination revealed that he had a palpable mass about 6.0 cm × 5.0 cm in size at the posterior axillary line in the right low back with skin ulceration 3 mm in diameter and exudation on it. Magnetic resonance imaging showed hydronephrosis of the right kidney and plaque-like abnormal signal in the middle portion of the kidney. The patient underwent a right nephrectomy. The sinus tract formation between the ulcerative skin in the right low back and the middle portion of the right kidney could be found. The distended kidney could not be excised entirely for tight adhesion. Pathological examination showed moderately differentiated renal squamous cell carcinoma with invasion of the renal parenchyma and perirenal adipose tissue. CONCLUSION: It is extremely rare for renal squamous cell carcinoma to present as skin invasion. Recurrent percutaneous nephrolithotomy may be a risk factor for squamous cell carcinoma of the renal pelvis. The possibility of renal squamous cell carcinoma should be kept in mind in patients who have hydronephrosis, nephrolithiasis, or chronic pyelonephritis for a long time or with renal anomalies. More radiological examinations are suggested for such patients.