Species: Mouse Strain/breeder: v-Ha-ras (TG.AC) OncoMouseTM /Taconic Sex: Male Age: 266 days Study type: Life-span Treatment: None Animal status: Killed moribund Clinical findings: Poor general condition, loss of body weight Organ(s): Mandible Gross finding(s): Mandible: firm, brown-white mass, size: 8 x 6 mm; mandibular lymph nodes: enlarged Staining: H&E Literature: Wright et al. (1995). Arch Oral Biol 40: 631-638

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Abstract

S. Rittinghausen and H. Ernst

Fraunhofer Institute of Toxicology and Experimental Medicine, Department of Pathology, Hannover, Germany

Key words: Ameloblastoma, odontogenic tumors, mouse, transgenic mice

An untreated 28-week-old male transgenic v-Ha-ras mouse was killed in a moribund condition. A complete necropsy was performed and, at the mandible, a firm, brown-white mass, sized 8 x 6 mm, was found in addition to enlarged mandibular lymph nodes. All organs were investigated histopathologically, the bones including the mandibular mass after decalcification.

Microscopically, the mandibular nodule was composed of anastomosing strands of epithelial cells embedded in a collagenous stroma. The epithelium consisted of a peripheral layer of columnar cells and loosely arranged central cells similar to stellate reticulum. The microscopic findings were concordant with the diagnostic features of an ameloblastoma of plexiform type.

A variety of immunohistochemical reactions against intermediate filaments were performed. The tumor showed areas positive for a pan-cytokeration, Ck 1, 4, 5, 6, 7, 14, 15, and 17, as well as for S100 A6 and vimentin.