| Abstract|| |
Primary renal leiomyomas are very rare benign tumors of the kidney, arising from smooth muscle cells of the renal capsule, pelvis or blood vessels. Simultaneous occurrence of a leiomyoma with conventional renal cell carcinoma (RCC) in the same kidney is an extremely rare incidence. Herein we describe a case, which to the best of our knowledge is the second reported case in the English literature. This 70-year-old female presented in surgical out-patient department with the complaints of hematuria and abdominal pain. Subsequently, on computed tomography a multifocal mass was noted in the right kidney, measuring 4.5 cm Χ 3 cm Χ 2 cm and 1 cm Χ 0.5 cm Χ 0.5 cm respectively. A radical nephrectomy was performed with the clinical diagnosis of a multifocal RCC. Histopathological examination revealed a conventional RCC in the larger nodule, whereas the smaller nodule showed a sub capsular leiomyoma, which was immune-positive for smooth muscle actin and HMB45. In the index case, radiology could not differentiate between the RCC and leiomyoma. Apart from being a radiological diagnostic dilemma, rare HMB45 immunostain positivity in capsular leiomyoma may create diagnostic dilemma for histopathologists too. Sole HMB45 positivity should not distract one to diagnose this lesion as an angiomyolipoma, unless the other components are seen.
Keywords: Diagnostic dilemma, HMB45 immunostain, renal cell carcinoma, renal subcapsular leiomyoma
|How to cite this article:|
Maneesh VK, Kumar R, Aggarwal S, Das P. Conventional renal cell carcinoma with renal capsular leiomyoma: A diagnostic dilemma. Indian J Pathol Microbiol 2013;56:393-5
|How to cite this URL:|
Maneesh VK, Kumar R, Aggarwal S, Das P. Conventional renal cell carcinoma with renal capsular leiomyoma: A diagnostic dilemma. Indian J Pathol Microbiol [serial online] 2013 [cited 2020 Feb 20];56:393-5. Available from: http://www.ijpmonline.org/text.asp?2013/56/4/393/125329
| Background|| |
Primary renal leiomyomas are benign smooth muscle tumor of kidney. They arise from smooth muscle cells of the renal capsule, pelvis, calices or blood vessels.  More than 100 cases of renal leiomyoma have been reported in the English literature detected mostly during autopsy procedure. In autopsy series, the prevalence of this lesion is found to be approximately 5% with a much lower clinical incidence. , To the best of our knowledge, only a single case report exists in literature having multi-locular cystic renal cell carcinoma (RCC) with presence of a leiomyoma in same kidney.  Herein we report a case of conventional RCC with simultaneous sub-capsular leiomyoma in the right kidney in a 70-year-old female who presented with complains of hematuria and abdominal pain. The purpose is to highlight and make people aware of the clinical, radiological and pathological diagnostic dilemmas one can face when encounter a similar lesion.
| Case Report|| |
This was a case report of a 70-year-old female patient who presented with the complaints of hematuria and abdominal pain for 2 months. On clinical examination, there was a palpable swelling in the right lumbar region, which moved with respiration. Urine analysis showed microscopic hematuria. Ultrasonography abdomen and subsequent computed tomography revealed two isolated lesions, one in the lower pole and the other in the mid zone of right kidney, measuring 3.5 cm × 3 cm × 2 cm and 1.0 cm × 0.5 cm × 0.5 cm respectively. A radical nephrectomy was performed with the clinical diagnosis of multifocal RCC. Post-operative recovery was uneventful. On gross examination, the kidney measured 12 cm × 8 cm × 5.5 cm. On cutting open a well-demarcated, variegated and golden-yellow tumor was identified in the lower pole of the kidney, measuring 3.5 cm × 3 cm × 2 cm in size. Tumor showed areas of hemorrhage and necrosis [Figure 1]a, Black arrow]. Another well-circumscribed and homogenous whitish lesion was seen in the middle zone of outer cortex in the sub-capsular region measuring 1.0 cm × 0.5 cm × 0.5 cm [Figure 1]b, Green arrow]. Rest of the kidney appeared normal. Histopathological examination of the sections from larger nodule showed a tumor composed of diffuse sheets of large clear cells with centrally placed mildly pleomorphic nuclei with areas of hemorrhage and necrosis. The pathological diagnosis was a conventional RCC, Fuhrman's grade 1. Microscopic examination of sections from the smaller nodule showed a well-circumscribed mesenchymal lesion comprising of intersecting fascicles of spindle shaped cells with a minimal pleomorphism. Increased mitotic activity was not noted [Figure 2]a-d]. The spindle shaped tumor cells were immunopositive for smooth muscle actin vimentin and HMB-45, while they were negative for CD-10 [Figure 3]a-d. Based on these morphological and immunohistochemical features a diagnosis of a sub-capsular leiomyoma was offered.
|Figure 1: Gross photographs show a nephrectomy specimen with aheterogeneous infi ltrati ng lower pole tumor (black arrows) and a small whiti sh sub-capsular fi rm nodule in the middle of the kidney (green arrow). Extensions into the renal pelvis as well as peri-nephric fat are not seen for both lesions|
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|Figure 2: Photomicrographs show well circumscribed subcapsular renal tumor comprising of intersecti ng fascicles of smooth muscles (a and b) (H and E ×100). Secti ons from the tumor in lower pole show features of a conventi onal clear cell RCC with nuclear features amounti ng to Fuhrman's' grade 1 (c and d) (H and E ×100)|
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|Figure 3: Immunohistochemical (IHC) stains performed on the renal subcapsular lesion showed negati vity for CD10 (a) (IHC [CD10] ×100) and positi vity for smooth muscle acti n (SMA) (b) (IHC [SMA] ×100) vimenti n (c) (IHC [Vimenti n] ×100) and HMB45 (d) (IHC [HMB45] ×100). The adjacent normal renal tubules show positi vity for CD10 immunostain (a) (IHC [CD10] ×100)|
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| Discussion|| |
Renal leiomyomas are often detected incidentally having 4.2-5.2% incidence in autopsy series.  In a study by Andreoiu et al., on 1030 nephrectomies performed over a period of more than 10 years, the authors showed that renal leiomyomas accounted for 1.5% of the benign renal tumors and 0.3% of overall kidney tumors.  In an article in 1990 Steiner et al., divided these lesions into two groups (1) Small tumors, asymptomatic, incidentally detected during autopsies or after radical nephrectomies and (2) Large tumors, symptomatic or presenting as a palpable abdominal mass.  Further in 1997, Wagner et al. added a third group: large tumors detected radiologically, without sign and symptoms.  According to Steiner et al., among symptomatic leiomyomas, tumor localization was sub-capsular in 53%, capsular in 37% and was in renal pelvis in the rest 10% cases. The main differential diagnosis of this lesion is angiomyolipoma of the kidney and spindle cell melanoma. Angiomyolipoma is composed of variable proportion of mature fat, myelocytes, thick walled blood vessels and smooth muscle cells. AMLs show immunoexpression for both HMB-45 and smooth muscle markers. In our case, the smaller lesion was positive for HMB-45, smooth muscle actin, vimentin and was negative for CD-10, creating a diagnostic dilemma with AML. Bonsib et al. demonstrated cortical leiomyomas with focal HMB-45 positivity and suggested a possible relationship with tumors of the perivascular epithelioid cell family.  In addition, some of the authors have demonstrated HMB-45 expression in the leiomyomas of capsular origin, whereas the same was negative in leiomyomas developing in the renal pelvis.  HMB-45 immunostain positivity in this case created a diagnostic dilemma for us with possibilities of AML or spindled malignant melanoma. Absence of other components of an AML and lack of cellular pleomorphism for malignant melanoma, ruled out these lesions. HMB45 immune-positivity possibly indicates hamartomatous origin of these groups of tumors.
Occurrence of renal leiomyoma in association with RCC in the same kidney is rare. Radiologically, it is often difficult to differentiate between these two lesions and they may be interpreted as multifocal RCC, like the index case. Histopathology is the only way to confirm the two lesions of different therapeutic significance. To the best of our knowledge, only one case report having multilocular cystic RCC with renal leiomyoma in the same kidney exists in the English literature. The present case is possibly the second example of the same entity. However if could be diagnosed pre-operatively and would have been considered in differential diagnosis, a nephron sparing surgery would have sufficed. Here we did not look for molecular associations of these two lesions, which would have been interesting. However lack of fresh frozen tissue was a deterrent.
| Conclusion|| |
Herein we have reported a very rare case of RCC with sub-capsular leiomyoma in the same kidney. Sole HMB45 positivity in the renal sub-capsular lesions should not make one to diagnose straight way as angiomyolipoma or malignant melanoma, as sub-capsular renal leiomyoma can show HMB45 positivity. This stain should be performed in spindle cell renal tumors with smooth muscle differentiation identified in tru-cut biopsy. If diagnosed pre-operatively, a nephron sparing surgery may be undertaken.
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Department of Pathology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi - 110 029
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3]