Renal interstitial cell tumor in a dog: clinicopathologic, imaging, and histologic features

Abstract

Renal interstitial cell tumors are benign tumors of renomedullary origin; however, malignant features have not been reported in dogs, to our knowledge. A 17-y-old spayed female Maltese dog was presented to a local animal hospital with a mass in the right abdomen. Clinicopathologic findings prior to surgery revealed renal insufficiency and anemia. Imaging revealed that the right kidney was enlarged by an amorphous mass with opaque areas, indicative of mineralization. Upon histologic examination, the mass was comprised of malignant mesenchymal cells that produced mucinous matrix. The tumor cells were positive for vimentin and COX-2, but negative for pancytokeratin; the matrix stained positively with alcian blue. Therefore, the mass was diagnosed as a renal interstitial cell tumor, with malignant features. COX-2 may be useful in the diagnosis of canine renal interstitial cell tumors, similar to its diagnostic role in humans.

Metastatic renal interstitial cell tumor in a dog

“…A diagnosis of RICT was achieved based on the morphologic and IHC features of the mesenchymal neoplasm in the kidney, myocardium, and brain. 5,6,8 Similar to descriptions of RICTs in dogs, tumors were bilateral and multiple. 6 Histologically, RICTs need to be distinguished from renal fibromas and other renal sarcomas.…”

“…Second, the presence of an extracellular AB-positive myxomatous matrix is a typical feature described in RICTs but not in renal fibromas. 5 Third, cytoplasmic immunolabeling for both vimentin and COX-2 is highly supportive of a diagnosis of RICT and a useful finding to rule out a fibrosarcoma (which should be negative for COX-2), as described in RICTs in dogs and humans. 5,8 A vascular neoplasm was ruled out based on the lack of immunolabeling for factor 8–related antigen.…”

“…5,8 A vascular neoplasm was ruled out based on the lack of immunolabeling for factor 8-related antigen. 5 Although sarcomatoid differentiation can occur rarely within canine and human RCCs, no evidence of an epithelial component was observed in the multiple tissue sections of kidney, myocardium, and brain in our case. 7 In humans, RICTs are typically incidental findings detected during autopsy.…”

“…5,6 Most canine RICTs are clinically benign, 5,6 with a single RICT case that had morphologic features of malignancy. 5 To our knowledge, no metastatic RICT has been reported in dogs to date. 5,6 Herein we describe a metastatic RICT in a dog.…”

“…Primary renal neoplasms are uncommonly diagnosed in dogs, 4 comprising <2% of all reported canine neoplasms diagnosed during autopsy. 1,5 The most common primary renal neoplasm in dogs is renal cell carcinoma, a malignant tumor arising from epithelial cells of the nephron. 7 Less frequent neoplasms include multiple types of renal sarcoma and nephroblastoma, which arise from renal mesenchymal cells and from the primitive metanephric blastema, respectively.…”