January 2018

Slide A:  Signalment (JPC #1655998):  Older, adult German shepherd dog, gender unspecified

HISTORY:  A renal mass was taken at necropsy.

HISTOPATHOLOGIC DESCRIPTION:  Kidney:  Expanding the renal cortex, compressing adjacent glomeruli and tubules, and extending to cut borders is a greater than 2 cm, well-demarcated, partially encapsulated, densely cellular neoplasm composed of uniform polygonal cells arranged in tubules, islands, trabeculae, and solidly cellular areas.  Neoplastic cells are supported by fine, wispy strands of fibrovascular stroma, which often contains large, ectatic vessels.  Neoplastic cells have indistinct cell borders and small amounts of finely granular, eosinophilic cytoplasm with occasional 2-4 um clear intracytoplasmic vacuoles.  The nuclei are irregularly round, with finely stippled chromatin and 1-2 variably distinct nucleoli.  The mitotic rate is less than 1/10 HPF.  Multifocally scattered throughout the neoplasm, there is single cell necrosis and small amounts of hemorrhage.  Within the adjacent cortical interstitium, there is mild, multifocal interstitial fibrosis with multifocal aggregates of few lymphocytes, plasma cells and rare macrophages.  There is mild atrophy and loss of adjacent tubules, and surrounding tubules are often mildly ectatic, lined by attenuated epithelium, and contain eosinophilic material (atrophic).  Multifocally, the parietal epithelium of the glomerulus is mildly hypertrophied; Bowman’s capsule is moderately thickened; and the uriniferous space is dilated and contains small amounts of proteinaceous material.  Sclerosis of the glomeruli is multifocally present.

MORPHOLOGIC DIAGNOSIS:  Kidney:  Renal cell carcinoma, mixed, German shepherd dog, canine.

Slide B:  Signalment (JPC #1804128):  A 768-day-old, Fischer 344 rat, gender unspecified

HISTORY:  A 1 cm diameter, cream-colored mass located on the anterior pole of the left kidney was removed from this rat, which was used as a control animal in a two-year feeding study.

HISTOPATHOLOGIC DESCRIPTION:  Effacing the cortex and medulla, elevating the renal capsule, and compressing the adjacent parenchyma is an irregular, 1x1cm, well-circumscribed, unencapsulated, multilobulated neoplasm.  Neoplastic cells are polygonal and arranged in islands and trabeculae that are separated by thin bands of fibrovascular stroma and anastomosing trabeculae of well-differentiated (metaplastic) bone.  Neoplastic cells have distinct cell borders with either abundant, foamy, eosinophilic cytoplasm or cytoplasm containing one or more irregular, discrete, clear vacuoles that marginate the nucleus.  Nuclei are round to oval with moderately coarse stippling of chromatin and 1-3 variably distinct nucleoli.  There is mild anisokaryosis and moderate anisocytosis.  The mitotic rate averages 2 per 10 HPF.  There is scattered single cell necrosis, hemorrhage and red crystals (hemoglobin).  Adjacent to the neoplasm, there is mild interstitial fibrosis with tubular atrophy and loss.  Multifocally, tubules are variably ectatic, lined by attenuated epithelium, and contain homogeneous, brightly eosinophilic, proteinaceous material (proteinosis).  The interstitium multifocally contains moderate numbers of lymphocytes mixed with fewer macrophages and plasma cells.

MORPHOLOGIC DIAGNOSIS:  Kidney:  Renal cell carcinoma, mixed, with stromal osseous metaplasia, F344 rat, rodent.

SYNONYMS:  Renal adenocarcinoma, malignant nephroma, clear cell carcinoma, hypernephroma, Grawit’s tumor











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