Renal Leiomyoma: Case Report and Literature Review

Abstract

Renal leiomyomas are rare benign tumors of the kidney originating from muscle cells. They are usually found by an autopsy, whether the patient is asymptomatic or has symptoms (i.e., abdominal/flank pain, hematuria, and palpable mass). Today the widespread use of ultrasonography and CT has increased the detection of clinically asymptomatic renal leiomyomas. The differential diagnosis between leiomyomas and other malignant lesions (above all renal cell carcinoma or leiomyosarcoma) is still possible by histologic examination. Radiologic examinations are not sufficient for the differential diagnosis. Renal leiomyomas have no aggressive behavior and they usually do not metastasize. The prognosis, after surgery, is excellent without recurrence. We report a case of leiomyoma in a 78-year-old man who presented with hematuria and flank pain. We also review the literature and provide a summary of clinical, radiologic, and histologic features of renal leiomyomas.

Introduction

Renal leiomyomas are rare benign tumors of the kidney originating from muscle cells. Differential diagnosis between leiomyomas and other malignant lesions is not possible with imaging, but only with histopathologic examination.¹ We report a case of leiomyoma in a 78-year-old man who presented with hematuria and flank pain. We also review the literature and provide a summary of clinical, radiologic, and histologic features of renal leiomyomas.

Clinical History

A 78-year-old male presented in the emergency department with hematuria and abdominal pain on the right flank. Noncontrast CT scan was performed as stone protocol that revealed right vesicoureteral junction 2 mm stone that was managed with medical expulsive therapy.

On the right renal upper pole, there was a simple cyst.

Also, there was an incidental finding of left upper pole exophytic renal mass, 1.5 cm, suspicious of renal cell carcinoma.

Methods

A triphasic CT scan of the lesion was done, described as a small well-defined focal-enhancing renal cortical lesion, measuring 1.5 × 1.2 cm demonstrating enhancement that is in precontrast ∼40 Hounsfield units (HU) and postcontrast 90 HU.

Since the only way to confirm the diagnosis is through histopathologic analysis that may be done with a renal needle core biopsy or a surgical excision, the patient was counseled for all management options including renal biopsy and radiofrequency ablation of the tumor, but the patient was worried and wanted to get rid of this mass.

The patient had good performance status, underwent laparoscopic partial nephrectomy transperitoneal approach, renal pedicle was dissected, and both renal artery and vein were identified, small renal mass wedge resection was done with a safety margin using cold scissor, and diathermy for the bleeding points and without any ischemia and renorrhaphy was done using 3/0 polydioxanone continuous suture with Hem-o-lok at the start and the end of the suture line, a powder hemostatic absorbable agent was used (Arista™) with an operative time 90 minutes and blood loss ∼100–200 mL.

The patient had no postoperative complications and was discharged home after 2 days.

Results

On gross examination, the mass was circumscribed and encapsulated with a well-defined limit between the thin rim of renal tissue and the lesion measuring 1.5 × 1.5 × 0.5 cm. Immunohistochemical stains show that tumor cells are positive for smooth muscle actin, focally positive for Desmin and negative for HMB45, S-100, Pan CK, and CD34. This immunohistochemical profile is consistent with renal leiomyoma (Fig. 1).

FIG. 1.

Contrast enhanced axial and coronal computed tomography of the abdomen shows a small, poorly enhancing lesion involving the upper pole of the left kidney. The mass is mainly hypodense and few foci of enhancement are present within the lesion.

Discussion

Leiomyomas are rare benign mesenchymal tissue tumors originating from smooth muscle cells. They were described first time by Virchow in 1854.¹ Leiomyomas are more common in the uterus. Although leiomyomas may involve any organ of the genitourinary tract, they most commonly affect the kidney. Leiomyomas originate from smooth muscle cells of renal capsule, pelvis, calices, and blood vessels.³

Renal leiomyomas may be triggered by a genetic predisposition followed by an acquired insult. Carpenter and colleagues demonstrated breakpoints in the q13–15 region of chromosome 12 in leiomyomas and congenital mesoblastic nephroma. Tsujimura and colleagues suggested an association between tuberous sclerosis and renal leiomyomas. Moreover, Krishnan and colleagues showed that Epstein–Barr virus infection could also lead to renal leiomyomas in immunocompromised patients.²

Renal leiomyoma is a rare benign tumor with autoptic evidence of 4.2% to 5.2%. In a recent review developed by the J. B. Brady Urological Institute (Baltimore, MD), in a period >10 years on 1030 nephrectomies performed, renal leiomyomas represented 1.5% of benign renal tumors and 0.3% of overall tumors treated. Leiomyomas are often detected incidentally. The cases reported in the literature suggest that these tumors affect adult women most frequently. The average age of presentation is 42 years. More than half of the cases present with pain and a palpable mass and 20% present with hematuria.²

Steiner and colleagues divided renal leiomyomas into two groups on the basis of the clinical features: (1) small tumors, asymptomatic, sometimes multifocal, incidentally detected in autopsy or after radical nephrectomy and (2) big tumors, often singular lesion, clinically manifested by symptoms/signs as pain or abdominal palpable mass. However, during past 15 years, the widespread use of ultrasonography and CT has increased the detection of clinically asymptomatic renal leiomyomas. In 1997, Wagner and colleagues added a third group to this classification: composition of tumors large enough to be detected radiographically, but without clinical signs and symptoms.⁴

In the first group of tumors, the average size is smaller than 5 mm, while “symptomatic” leiomyomas have an average width of 12.3 cm and an average weight of 1.84 kg. As of today, the biggest renal leiomyoma is 57.5 cm with a weight of 37.2 kg.

Macroscopically the renal leiomyoma is described as a white or red peripheral lesion, well-defined, with a solid aspect and elastic consistence. Color is related to mass vascularization.

According to Steiner and colleagues, among symptomatic leiomyomas, tumor localization is subcapsular in 53%, capsular in 37%, and of renal pelvis in 10%. In addition, lesions >12 cm may have cystic degeneration and hemorrhagic areas in 17% and 27% of cases, respectively. The cystic degeneration is not necessarily associated with sarcomatoid degeneration.

Histologically, renal leiomyomas appear to be made of fusocellular elements showing the absence of mitotic figures, pleomorphism, hypercromatism, and, above all, the absence of perilesional invasivity. The presence of these conditions is characteristic of leiomyosarcoma.

The main differential diagnosis is usually made with angiomyolipoma (AML) of the kidney. AML is a benign mesenchymal tumor composed of a variable proportion of adipose tissue, spindle and epithelioid smooth muscle cells, and abnormal thick-walled blood vessels. Most AMLs are composed of a variable mixture of mature fat, thick-walled blood vessels, and smooth muscle, but there are times when only a smooth component is the most represented. AMLs are characterized by a coexpression of melanocytic marker (HMB45) and smooth muscle markers. Bonsin and colleagues showed a focal expression of HMB45 in cortical leiomyomas and suggested a relationship between AMLs and other tumors of the perivascular epithelioid cell family.⁴

Currently, the differential diagnosis between leiomyoma and leiomyosarcoma is only histopathologic after nephrectomy because the radiologic aspect is not a diriment in the diagnosis. Ultrasonographic evaluation detects leiomyoma as a hypoechoic lesion that could appear solid or cystic.

Derchi and colleagues described some CT scan features helpful for the differential diagnosis. The first feature is density. All leiomyomas examined before contrast were hyperdense compared with the kidney, with density similar to that of muscles. After contrast medium injection, the lesions had a lower enhancement than surrounding renal parenchyma. The second and final feature is localization and margins. Usually, these lesions have a peripheral location with well-defined margins, with no signs of infiltration into surrounding tissues. In a patient with these radiologic features, leiomyoma is part of the differential diagnosis, but does not rule out malignant diseases.²

In these cases, surgery is still the gold standard. In suspicious cases, radical nephrectomy is the typical approach with an excellent prognosis. In cases of small lesions (≤4 cm), it is possible to opt for conservative surgery. A further option for smaller lesions is renal biopsy, although this solution is still controversial.

Conclusion

Renal leiomyomas are benign, and their behavior is not aggressive. They do not metastasize. The prognosis, after surgery, is excellent without recurrence. This case reflects the clinical and radiologic features described in the literature. It further illustrates how difficult it is to distinguish clinically a leiomyoma from other malignant lesions. Differential diagnosis is still possible by histologic examination.

Abbreviations Used

AML

angiomyolipoma

CT

computed tomography

HU

Hounsfield units

Disclosure Statement

No competing financial interests exist.

Cite this article as: Aldughiman AW, Alzahrani A, Alzahrani T (2019) Renal leiomyoma: case report and literature review, Journal of Endourology Case Reports 5:4, 181–183, DOI: 10.1089/cren.2019.0049.