A Case Report of a Renal Mixed Epithelial and Stromal Tumor in a Heterozygous S1P2 Receptor Deficient Mouse

Abstract

ABSTRACT. We report a case of mixed epithelial and stromal tumor of the kidney (MESTK) in a 32-week-old heterozygous sphingosine 1-phosphate-2 (S1P2) receptor deficient female mouse. A white solid mass replacing the left kidney was observed at the left retroperitoneal wall. Histologically, the tumor mass consisted of dimorphic cellular components of epithelial and stromal cells. Epithelial cells formed various sized irregular-shaped tubular structures resembling renal tubules surrounded by stromal cells. Immunohistochemically, epithelial cells were positive for cytokeratin, while stromal cells showed positive immunoreactivity with α-smooth muscle actin as well as vimentin. Based on the morphological and immunohistochemical findings, this tumor was diagnosed as a MESTK. KEY WORDS: N-ethyl-N-nitrosourea, renal mixed epithelial and stromal tumor, S1P2 deficient mouse.J. Vet. Med. Sci. 70(5): 483-485, 2008 This report describes a case of mixed epithelial and stromal tumor of the kidney (MESTK) in a female heterozygous sphingosine 1-phosphate-2 (S1P2) deficient C57BL/6N mouse of 32 weeks old. S1P2 is a member of the G proteincoupled receptor family (formerly called the EDG family) that binds and mediates a variety of actions of sphingosine-1-phosphate, a plasma-derived pleiotropic sphingolipid mediator. A heterozygous S1P2-deficient female mouse which received a single subcutaneous injection of 120 mg/ kg body weight of N-ethyl-N-nitrosourea (ENU) at 6 weeks of age was subjected to complete necropsy on 32 weeks of age. Until necropsy, this mouse did not show any abnormal clinical signs. At necropsy, a white solid mass (15 mm × 10 mm × 10 mm) replacing the left kidney without involving the surrounding tissues was observed at the left retroperitoneal wall. While 3 groups of mice including wild type mice (n=14), heterozygous S1P2 deficient mice (n=9), and homozygous S1P2 deficient mice (n=8), all given ENU, were allocated, such a renal tumor was not observed in the other ENU-treated mice. On cut section, a mass was white, firm and mottled with hemorrhagic foci. No other particular pathologic abnormalities were observed in this mouse. The mass was fixed in 10% neutral buffered formalin and processed for routine histopathology with hematoxylin and eosin. Periodic acid-Schiff (PAS) staining was also applied on this tumor. As immunohistochemical analysis, avidinbiotin-peroxidase complex (ABC) technique was applied using antibodies against α-smooth muscle actin (monoclonal mouse antibody, clone 1A4; DAKO, Glostrup, Denmark), cytokeratin (monoclonal mouse antibody, clone MFN116; DAKO), desmin (monoclonal mouse antibody, clone D33; DAKO), estrogen receptor (monoclonal mouse antibody, clone 6F11; Novocastra Laboratories, Newcastle upon Tyne, UK), vimentin (polyclonal goat antibody, product no.C-20, Santa Cruz Biotechnology, Santa Cruz, CA) and WT-1 (polyclonal rabbit antibody, product no.C-19, Santa Cruz Biotechnology). These slides were lightly counterstained with hematoxylin. Appropriate positive and negative control tissu...

Spontaneous Renal Mixed Epithelial and Stromal Tumor (MEST) in a Beagle

“…Mixed epithelial and stromal tumor (MEST) of the kidney is a rare benign cystic renal tumor in animals and humans and is predominantly seen in females [1][2][3][4][5][6] . The tumor is characterized by mixture of epithelial and stromal elements, and the epithelial elements have cystic and tubular growth patterns.…”

“…MEST of the kidney is rare neoplasm in humans. In animals, MEST of the kidney has been reported in a female ringtail lemur (Lemur catta) and heterozygous sphingosine 1-phosphate-2 (S1P2) receptor deficient female mouse 4,6 . In those studies, the masses grossly formed as a large solid and c y s t i c m a s s a n d o c c u p i e d t h e l e f t k i d n e y .…”