Rare case of renal cell carcinoma presenting as a cutaneous horn

Cutaneous metastases are a rare and generally late manifestation of renal cell carcinoma (RCC). Because they can mimic other dermatologic lesions, they may pose a diagnostic challenge if there is not a high degree of suspicion of their underlying cause.


Louise Zhou, MD, Taren Ohman, MD, and Robert Zaiden, Jr., MD

Department of Medicine, University of Florida College of Medicine, Jacksonville, FL

Cutaneous metastases are a rare and generally late manifestation of renal cell carcinoma (RCC). Because they can mimic other dermatologic lesions, they may pose a diagnostic challenge if there is not a high degree of suspicion of their underlying cause.

Case presentation

A 61-year-old man presented with a right leg mass initially noted as a pimple-like lesion that enlarged rapidly over 2 weeks. This lesion was extremely painful to touch, and the patient had also noticed the appearance of adjacent leg varicosities. He denied any recent trauma or insect bites. Review of systems revealed an unintentional 30-lb weight loss in the past 6 months as well as progressive dyspnea on exertion and intermittent chest pain for 4 months prior to presentation. The patient had a history of smoking half a pack of cigarettes a day for 12 years; however, he quit 10 years ago.

Physical examination showed a large, 3.7 cm × 3.5 cm × 2 cm, malodorous, moist, exophytic friable mass located on the lateral aspect of his right lower extremity, 5 inches above the lateral malleolus (Figure 1). The lesion was smooth yet firm, yellow-tan to purplish-black without any surrounding erythema. It was slightly gelatinous and bled easily with minor trauma. Prominent dilated veins spanned the length of the patient’s right leg, from his groin to his foot. There was no appreciable lymphadenopathy or abdominal mass.

Laboratory data were significant for anemia, with a hemoglobin level of 5.8 g/dL and hematocrit of 18.9%; thrombocytosis, with a platelet count of 447,000 cells/mm3; and hypercalcemia, with a corrected serum calcium level of 11.5 mg/dL. The patient was hospitalized for packed red blood cell transfusions and further workup of his leg mass.

A biopsy revealed the mass to be metastatic clear cell RCC (Figure 2). A CT scan of the chest, abdomen, and pelvis showed a large, 9.2 cm × 11 cm, heterogeneously enhancing mass with necrotic components arising from the mid and inferior poles of the right kidney (Figure 3). Multiple necrotic mediastinal and bilateral hilar lymph nodes; numerous scattered pulmonary nodules; innumerable enhancing hepatic masses; and lytic lesions in the thoracic, lumbar, and iliac bones were also noted. A CT scan of the brain was negative.

The patient’s hospital course was subsequently complicated by the onset of persistent hematuria, despite continuous bladder irrigation. He was started on sorafenib (Nexavar), and a follow-up appointment was scheduled with oncology upon discharge; however, the patient decided to enroll in inpatient hospice instead.


RCC comprises 90% of primary renal neoplasms, and 85% of them are clear cell type.1 RCC represents 2%–3% of all cancer diagnoses; however, rates have steadily increased by 2% each year in the past 65 years, with unknown cause.2 Smoking and obesity are known risk factors. As the use of imaging modalities, such as ultrasonography and CT scans of the abdomen and pelvis, has become more prevalent, the frequency of incidental detection of RCC has increased also.Fewer than 9% of patients with RCC present with the classic triad of hematuria, flank pain, and palpable abdominal mass.3 Indeed, its presentation can be so varied and nonspecific that it is deservedly called the internist’s tumor.

Cutaneous metastases

Most RCCs are clinically silent in their natural course, and their presence may not be discovered until the disease is either locally advanced and unresectable or metastatic. The most common sites of metastasis are the lungs, liver, brain, bones, and adrenal gland.3 Cutaneous metastases are relatively rare, with an incidence of 3.4%.4 The most common sites for cutaneous metastases are the head and neck region followed by the trunk, whereas in our patient, the lesion was located more distally on the leg.

Given the high vascularity of RCC, distant skin metastasis is believed to occur via hematogeneous spread. Cutaneous lesions can be flesh-colored but may also appear erythematous to violaceous, due to hemosiderin deposits in the dermis from its high vascularity. Lesions can be multiple but may infrequently present as solitary masses. Histologically, these lesions involve the dermis, with occasional extension into the subcutis. A grenz zone, a thin layer of superficial dermis separating the lesion from the epidermis, is usually present.

Due to the depth of invasion seen in these lesions, it is preferable to do an excisional or punch biopsy over a superficial shave biopsy so that dermal involvement is not missed. Cutaneous metastases are highly vascular, and a significant amount of bleeding may occur during biopsy. Most RCC cutaneous metastases are histologically consistent in appearance with clear cell adenocarcinoma. Other diagnostic techniques include immunohistochemical staining for vimentin and keratin.


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