leiomyomatous renal cell carcinoma

In 2006, five cases of renal cell carcinoma described as having angioleiomyoma-like stroma were described. Four similar cases had been previously reported in which angioleiomyoma-like stroma was admixed with clear cells that were interpreted as being either renal cell carcinoma or benign.

Since the publication of the original series two further reports have detailed the features of a further six cases.

Clinical details of these tumors were available for 12 cases. There were eight female and four male patients with ages ranging from 18 to 93 years (mean 54 years). In nine of the cases there was no significant past medical history. Two of the patients had co-existing cancer (breast carcinoma and papillary renal cell carcinoma) and one patient had tuberous sclerosis. In the majority of cases the tumors were incidental findings, although three patients presented with hematuria.

Grossly the tumors measured 1.8–14 cm (mean 4.6 cm) and were variously described as tan, brown, yellow or white with the frequent presence of a thick investing capsule. Microscopically the tumors are composed of nests, cords and sheets of epithelial cells frequently forming solid areas, tubules or papillary structures. There is minimal nuclear pleomorphism with abundant clear cytoplasm. The stroma has the appearance of mature smooth muscle (Figure 36) sometimes with scattered, often dilated vascular spaces. The stromal component of the tumor is often pronounced at the periphery and in some cases appears to extend into adjacent renal tissue or into perirenal fibrofat.

The epithelial component of the tumor showed positive immunoexpression of cytokeratins AE1/AE3, 7 and CAM 5.2, CD-10, S-100 protein (focal), EMA and vimentin. There was variable expression of 34E12, whereas smooth muscle actin and HMB45 was negative. The stroma component was positive for smooth muscle actin, caldesmon, desmin, vimentin and negative for HMB45, CD117, cytokeratins, EMA, ER and PR. Ultrastructural studies are limited to two cases and these showed the epithelial component to have features similar to clear cell renal cell carcinoma, whereas the stroma was typical of smooth muscle cells.

Genetic studies on these tumors are contradictory.118, 119 In three cases FISH showed loss of VHL and FHIT, with loss of chromosome 3 in one case and 3p in another. In a separate study there was no evidence of 3p deletion in the three cases examined.

The differential diagnosis for these tumors is clear cell renal cell carcinoma, angiomyolipoma with co-existing clear cell renal cell carcinoma and sarcomatoid renal cell carcinoma, although the presence of a pronounced smooth muscle stroma should present few diagnostic difficulties. Unlike clear cell renal cell carcinoma, the epithelial components of these tumors are positive for cytokeratin 7 and 34E12. The stromal component of leiomyomatous renal cell carcinoma has bland cytological features unlike that of sarcomatoid renal cell carcinoma and further there is no merging of the epithelial and stromal components.

Outcome studies for leiomyomatous renal cell carcinoma are limited. Of cases for which details are available, four were pT1a and one pT1b at diagnosis. No evidence of recurrence or metastases was seen in these and two other cases followed from 6 months to 5 years (mean 3 years).

References

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