An ALK translocation positive carcinoma of the lung presenting as uremia due to bilateral renal obstruction.

We describe an unusual presentation of metastatic lung adenocarcinoma as malignant retroperitoneal fibrosis (MRPF). The diagnostic challenge, due to the small solitary lung mass and absence of a discrete retroperitoneal mass, was overcome by diagnostic laparoscopy. Molecular analysis of tissue acquired was positive for ALK gene rearrangement. Treatment of the patient with crizotinib reversed MRPF. He was weaned off the nephrostomy tubes and is with stable renal function 11 months after diagnosis.