Lab Anim Res.  2013 Jun;29(2):127-130. 10.5625/lar.2013.29.2.127.

Uterine leiomyosarcoma in a wild rat (Rattus norvegicus): usefulness of Ki-67 labeling index for diagnosis

Affiliations
  • 1College of Veterinary Medicine and Institute of Veterinary Science, Kangwon National University, Chuncheon, Korea. byoon@kangwon.ac.kr
  • 2Toxicologic Pathology Divison, Korea Institute of Toxicology, Daejeon, Korea.

Abstract

Uterine smooth muscle tumor is very rare in laboratory rats and, there has been no report in the wild rodents. Among a total of 400 wild rats captured in Gyeonggi, Gangwon, and Chungbuk provinces of Korea in 2007, 2010, and 2011, we found a uterine spindle cell tumor, diagnosed as smooth muscle cell origin based on differential features of histology and immunohistochemistry. Its incidence was very low, like in the laboratory rats, as under 0.5% for female. Considering generally applied histological and cellular criteria, this case was difficult in differential diagnosis between benign and malignant. Ki-67 labeling index was therefore further investigated, and it ranged from 26.4 to 37.6% in the 10 different areas, representing an average of 32.9+/-0.05%. The Ki-67 labeling index of neoplastic cells near the necrotic area was recorded as 83.5%. According to such high Ki-67 labeling index, it was more likely a malignant leiomyosarcoma, assenting to the previous proposal that Ki-67 labeling index is a significant criterion to differentiate between malignant and benign in the smooth muscle tumors.

Keyword

Ki-67; leiomyosarcoma; Rattus norvegicus; rat

MeSH Terms

Animals
Diagnosis, Differential
Female
Humans
Immunohistochemistry
Incidence
Korea
Leiomyosarcoma
Myocytes, Smooth Muscle
Rats
Rodentia
Smooth Muscle Tumor

Figure

  • Figure 1 Gross finding of the masses (arrows) in both side of the uterus.

  • Figure 2 Histopathology (A, B) and immunohistochemistry for cytokeratin (C), vimentin (D), desmin (E), smooth muscle actin (F), S-100 (G) and Ki-67 (H, I). Note the strong immunoreactivity of the neoplastic cells for vimentin, desmin and smooth muscle actin, same as the smooth muscle fibers of blood vessels (arrows in E and F). Also note the very high Ki-67 index of the neoplastic cells near the necrotic area ("n" in B and I). In A, "e" and "l" represent endometrium and lumen, respectively.


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