Challenging case: A large ‘ticking’ back lipoma and a small renal mass

“Challenging Cases in Urology” is a new Urology Times section in which residents from the nation’s leading urology programs present their toughest cases and how they ultimately managed them. Cases inform readers of the problem-solving process and provide a lesson from the authors’ experience.

History

A 57-year-old man initially presents to a general surgeon with a chief complaint of right lower back and posterior neck pain, with associated soft tissue swelling. Eight months prior to referral to our institution, he underwent excision of these lesions, pathology of which showed benign lipomas. On presentation to our institution, he had experienced regrowth of the masses with "ticking" in the right lumbar area that he correlated with his heartbeat. He also reported unintentional weight loss of 15 pounds over the previous 3 months.

The patient’s past medical history was notable for hypertension, well controlled on oral medications, and glaucoma. Surgical history was remarkable for surgical excision of lipomas as noted above, and open reduction and internal fixation of a right elbow and wrist fracture. Family history revealed stomach cancer in his father, liver cancer in his mother, and no notable medical problems in his younger sister.

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He had a very brief and remote history of smoking, used alcohol rarely, and at the time of initial office visit was still actively working as a mechanical engineer.

Examination

On physical exam he was well nourished with a BMI of 29 kg/m², alert and oriented to person, time, and place. He rated his pain at a 7/10 on the right buttock and was unable to lie down for the exam because of this pain. His abdomen was soft, nontender, and without scars. Peripheral pulses were 2+ and there was no appreciable groin lymphadenopathy. He had a very large right lumbar and gluteal mass that was firm but did not show signs of skin involvement. There was an appreciable bruit on auscultation.

The upper mid portion had a well-healed 5-cm transverse incision. Extremities had no edema or cyanosis, with mildly decreased strength of his right leg.

Next: What lab, imaging studies showed

Laboratory and imaging studies

Laboratory analysis showed a normal complete blood count with a hemoglobin of 14, white blood cell count of 8, and platelet count of 229. Complete metabolic panel was notable for hypercalcemia with serum Ca 11.7 mg/dL; renal function was normal with creatinine of 0.74. A coagulation panel was normal, as were urinalysis and liver function tests.

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A contrast-enhanced MRI of the pelvis showed a 13 cm by 12 cm mass centered on the right gluteal region with extensive osseous and soft tissue involvement concerning for a malignant neoplasm. Specifically, the mass invaded the right iliac bone, right iliopsoas, gluteus medius and maximus, and S1-3 sacral foramina. The right gluteal arteries appeared enlarged.

Chest and abdomen CTs with intravenous contrast were subsequently ordered. CT chest showed multiple pulmonary nodules bilaterally and a large, expansile lytic lesion of the left scapula, all concerning for metastatic disease. CT abdomen demonstrated a 4-cm solid enhancing mass in the upper pole of the left kidney, abutting the renal sinus, without associated hydronephrosis (figure). Hydronephrosis and hydroureter were noted down to the pelvis on the rightside to the level of a 3x2-cm mass in the lateral upper right pelvis.

Contrast-enhanced commuted tomography, coronal section, demonstrating 4-cm renal mass in the left upper pole, dilation of the left collecting system, and large invasive right gluteal mass. (Photo courtesy of Molly E. DeWitt-Foy, MD, Kyle J. Ericson, MD, and Venkatesh Krishnamurthi, MD)

On further chart review, one prior non-contrast abdominal CT scan was identified from 12 years earlier; this identified no renal masses. An MRI brain was negative for intracranial metastasis.

Management

The patient underwent Tru-Cut needle biopsy of the right gluteal mass. Pathologic analysis was consistent with metastatic renal cell carcinoma, clear cell type.

Given the right-sided hydronephrosis, the decision was made to take the patient for cystoscopy and right ureteral stent placement. Cytoreductive nephrectomy was considered, but due to the extensive degree of metastatic disease and small primary tumor burden, non-operative management was favored.

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The patient was referred to medical oncology and elected to enroll in a clinical trial. He initially received immunotherapy with an anti-PDL1 antibody alone (atezolizumab [Tecentriq]), but due to progressive disease he crossed over to receive a combination of atezolizumab and bevacizumab (Avastin). He again progressed and ultimately was treated with axitinib (Inlyta), a small molecule tyrosine kinase inhibitor. Three years later his disease remains stable and he undergoes regular stent exchanges to manage his obstructed right renal unit.

Next: Small renal masses increasingly common

Discussion and diagnosis

Detection of small renal masses, measuring ≤4 cm, has increased significantly over the last 3 decades, largely due to the increase in cross-sectional abdominal imaging done for other purposes. Despite earlier detection and treatment of renal masses, the mortality for kidney cancer patients has not improved (J Natl Cancer Inst 2006; 98:1331–4). This may be indicative of biologic heterogeneity of these tumors, which is currently poorly understood.

Meta-analyses suggest 20% of small renal masses are benign, 60% display indolent growth behavior, and 20% are aggressive malignancies. Most small renal masses exhibit slow growth and up to 30% may not grow at all during a period of active surveillance. Indeed, the risk of metastatic disease for a small renal mass is less than 2% (J Urol 2006; 175:425-31).

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Here we present a patient who was found to have a small renal mass only after presenting with large-volume diffuse metastatic disease to the contralateral gluteal region causing obstructive uropathy of the unaffected kidney. Two biopsies were required to achieve accurate pathologic diagnosis. He was managed with an immune checkpoint inhibitor and targeted molecular therapy, as well as regular right ureteral stent exchanges.

Although cytoreductive nephrectomy can certainly be used in metastatic renal cell carcinoma, careful patient selection for debulking is essential. A number of studies have aimed to answer this question, and most would argue that patients with poor performance status and/or intracranial metastasis are unlikely to benefit from surgery (Ther Adv Urol 2015; 7:275-85). Indeed, in the recently published randomized CARMENA trial, sunitinib alone was non-inferior to cytoreductive nephrectomy in intermediate- and poor-risk patients (N Engl J Med 2018; 379:417–27). In addition, in order for debulking to be most useful, nephrectomy should remove at least 75% of total tumor volume (J Urol 1997; 158:1691-5).

For this patient, his primary tumor was significantly smaller than his metastatic burden, and partial or radical nephrectomy would be unlikely to change his response to chemotherapy or affect his overall survival. The chronic obstruction of this patient's contralateral renal unit is another important consideration; an unnecessary nephrectomy would put him at risk of renal insufficiency and limit his ability to receive chemotherapy.

Molly E. DeWitt-Foy, MD

Kyle J. Ericson, MD

Venkatesh Krishnamurthi, MD

Dr. DeWitt-Foy and Dr. Ericson are urology residents, and Dr. Krishnamurthi is a staff physician at the Cleveland Clinic Glickman Urological & Kidney Institute, Cleveland.