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Renal leiomyosarcomas are rare tumors of the kidney, comprising 0.5% to 1.5% of all malignant renal tumors in adults. A 65-year-old male presented with generalized weakness and flank pain in the right lumbar area for the last 8 months. Radiological imaging revealed a heterogeneous mass in the right kidney, with no lymphadenopathy or venous thrombosis. The tumor measured 15 cm at its greatest axis and replaced almost the entire kidney. His metastatic work-up was negative. He underwent right radical nephrectomy. Histopathology revealed spindle-shaped sarcoma; immunohistochemistry confirmed a primary renal leiomyosarcoma. The patient is doing well 1 year after surgery.
Suresh Kumar, Proshan Jeet, Ranjit Kumar Das, Anup Kumar Kundu, Sandeep Gupta
Submitted December 8, 2010 - Accepted for Publication February 27, 2011
KEYWORDS: Renal mass; Radical nephrectomy; Leiomyosarcoma
CORRESPONDENCE: Dr. Suresh Kumar, Department of Urology, Institute of Post Graduate Medical Education and Research, Seth SukhLal Karnani Memorial Hospital, 601, Doctors PG Hostel, 242 AJC Bose Road, Kolkata- 700020, West Bengal, India ().
CITATION: UroToday Int J. 2011 Jun;4(3):art34. doi:10.3834/uij.10.3834/uij.1944-5784.2011.06.05
ABBREVIATIONS AND ACRONYMS: CT, computed tomography; RCC, renal cell carcinoma.
Renal leiomyosarcomas are rare tumors of the kidney that were first reported by Berry in 1919 . They comprise 0.5% to 1.5% of all malignant renal tumors in adults . Prior to 1997, only 11 cases were reported in the English literature . Improved diagnostic methods make current reports more frequent. We describe a 65-year-old male who presented with generalized weakness and a lump in the right lumbar region. Radiologically, it was difficult to say whether a large soft tissue mass was renal cell carcinoma (RCC) or sarcoma of the kidney. Histopathology and further immunohistochemistry confirmed it to be a primary renal leiomyosarcoma.
A 65-year-old male presented with generalized weakness and a dull, aching pain in the right flank for the last 8 months. There was no history of hematuria or stone passage. On examination, the patient was markedly pallor. There was no evidence of jaundice, edema, or lymphadenopathy. A large lump was palpable. It occupied the right lumbar hypochondrium and extended superiorly to the epigastrium and inferiorly to the umbilicus. The region had very little movement during respiration. The lump was nontender with variable consistency. It was not ballotable but was bimanually palpable, with restricted lateral mobility. There were no signs suggestive of fluid in the peritoneal cavity.
The patient's hemoglobin was 4.8 g/dL. Total leukocyte count was 6.8x109/L with polymorphs 57%, lymphocyte 33%, monocyte 3%, and eosinophils 7%. Urinalysis showed no abnormality. Fasting blood sugar was 84 mg/dL. Urea was 22 mg/dL and creatinine was 1.1 mg/dL. Liver function tests were normal except for hypoproteinemia. A chest X-ray was normal. Contrast-enhanced computed tomography (CECT) of the abdomen showed a large heterogeneous mass replacing almost the entire right kidney. There was no lymphadenopathy and no evidence of venous thrombosis (Figure 1).
After transfusing adequate packed red cell and parenteral albumin therapy, the patient had surgery. He underwent a right open radical nephrectomy via a chevron incision. The postoperative period remained uneventful.
Grossly, the kidney showed a large tumor measuring 15 cm at its greatest axis; it replaced almost the entire kidney. Pathological TNM staging was T2NOMO with a negative resection margin. A cut section was grayish in color and fleshy in texture (Figure 2). Microscopically, the tumor was composed of interlacing fascicles of spindle-shaped cells with elongated plump nuclei. The tumor cells showed nuclear pleomorphism. Tumor giant cells with bizarre hyperchromatic nuclei and abundant eosinophilic cytoplasm and mitotic figures were present (Figure 3). Microscopic features were suggestive of spindle-shaped sarcoma that were compatible with a high-grade leiomyosarcoma.
To differentiate this tumor from the sarcomatoid variety of RCC, immunohistochemical staining was done. Van Gieson's and Masson's trichrome staining confirmed a smooth muscle origin. On immunohistochemical staining, the tumor was vimentin and smooth-muscle actin positive and cytokeratin and desmin negative, which confirmed primary renal sarcoma. At the patient's 6-month and 1-year follow-up examinations, abdominal CT-scan, chest X-ray, and liver function tests showed no abnormalities.
Renal leiomyosarcomas are the most common histological subtype of renal sarcomas, accounting for approximately 50% to 60% of the reported cases . Most often, these tumors are peripherally located and originate from the renal capsule or smooth muscle fibers of the renal pelvis or vessels. Onset most commonly occurs in the 5th to 8th decades. Women outnumber men in a 2:1 ratio.
Patients with renal leiomyosarcomas typically present with the classic triad of symptoms: (1) flank pain, (2) hematuria, and (3) abdominal mass mimicking RCC. A flank mass with pain is the characteristic presentation. An abdominal CT scan typically reveals a large solid mass involving or derived from the kidney, which is a finding similar to that of many sarcomatoid renal cell carcinomas. Diagnosis is usually made postoperatively. The tumor is intrarenal in only a third of the cases. Although the presence of fat or bone may suggest liposarcoma or osteosarcoma, most renal sarcomas demonstrate imaging features that are indistinguishable from the more common RCC . Grossly, the tumor is firm, fibrous, and multinodular with a bosselated surface , as in our case. Cystic areas are reported only in large leiomyosarcomas. A cystic mass with thick walls or a large heterogeneous mass with no lymphadenopathy or venous thrombosis on CT scan should raise the suspicion of sarcoma. Pathologically, this tumor mimics the sarcomatoid variety of RCC. Immunohistochemical staining helps to differentiate between the 2 tumor types.
Radical nephrectomy remains the treatment of choice. Surgical resection is the only independent predictor of survival . Preoperative and postoperative radiotherapy and chemotherapy do not affect the overall survival [8,9]. These patients have poor prognosis and rarely survive longer than 1 year. Leiomyosarcomas have a poor prognosis, even when confined to the kidney. Kendal  found that patients with leiomyosarcoma exhibited a median overall survival of 25 months, with a 5-year overall survival rate of 25%. The favorable prognostic markers are size < 4 cm, low grade, absence of nodal metastasis, and radical surgical treatment. The cystic component of the tumor may also help to predict the behavior. In our case, poor prognostic factors are the large tumor size and high grade, but a positive prognostic factor is the negative resection margin. Fortunately, our patient is doing well 1 year following surgery.
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