NEOPLASMS

In general, the incidence of spontaneous tumors in this species is relatively low, with increasing incidence in gerbils over 2 years of age, at which point the prevalence of tumors can become common.

FIG. 4.14. Cutaneous malignant melanoma from a Mongolian gerbil.

FIG. 4.16. Ovaries and uterine horns from an aged female Mongolian gerbil. The left ovary, which contains a dark red to pale granulosa cell tumor, is markedly enlarged, fleshy, and lobulated. (Source: D. Schlafer, Cornell University, Ithaca, NY. Reproduced with permission from D. Schlafer. )

that occur in different colonies of Mongolian gerbils. Cutaneous, ovarian, and adrenocortical tumors are the most commonly recognized neoplasms in this species. The most common cutaneous tumors are squamous cell carcinomas and melanomas. Melanomas (Figs. 4.14 and 4.15) tend to develop around the ear, nose, feet, and base of the tail. Squamous cell carcinomas, sebaceous adeno­mas, and adenocarcinomas of the ventral marking gland are relatively common in gerbils. In aged females, gran­ulosa cell tumors appear to be the most common ovarian neoplasm. Granulosa cell tumors are frequently bilateral and vary from fleshy and lobulated to cystic masses (Fig. 4.16). Transformed granulosa cells are sometimes identifiable microscopically in the ovary in the absence of macroscopic change. On histopathology, vascular spaces surrounded by aggregations of granulosa cells

FIG. 4.15. Renal lymph node with metastasis of malignant melanoma in a Mongolian gerbil.

are the typical patterns observed (Fig. 4.17). Dysgermi- nomas, luteal cell tumors, leiomyomas, and, rarely, the­cal cell carcinomas have been identified. Adrenal cortical adenomas and carcinomas also occur. Neoplasms of the lymphopoietic system are uncommon in gerbils. Leuke­mia with lymphoblastic infiltrates in spleen, liver, lymph nodes, and muscle was observed in an aged animal, and there are single case reports of primary cutaneous B-cell lymphoma and systemic mastocytosis. There is a relatively low incidence of tumors of the pituitary, mammary gland, and lung in the Mongolian gerbil. In a study involving other species of gerbillinae, neoplasms included squamous carcinoma of the ear, thymoma, Hodgkin-like lymphoma, uterine adenocar­cinoma, adrenocortical tumors, and primary ovarian tumors. Gastric carcinomas have been produced exper­imentally in gerbils inoculated with H. pylori.

FIG. 4.17. Granulosa cell tumor in a Mongolian gerbil. Note the prominent vascular spaces.

BIBLIOGRAPHY FOR NEOPLASMS

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Guzman-Silva, M.A. & Costa-Neves, M. (2006) Incipient spontane­ous granulosa cell tumour in the gerbil, Meriones unguiculatus. Laboratory Animals 40:96-101.

Matsuoka, K. & Suzuki, J. (1995) Spontaneous tumors in the Mongolian gerbil (Meriones unguiculatus). Experimental Animals 43:755-760.

Meckley, P.E. & Zwicker, G.M. (1979) Naturally-occurring neo­plasms in the Mongolian gerbil (Meriones unguiculatus). Labora­tory Animals 13:203-206.

Rembert, M.S., Coleman, S.U., Klei, T.R., & Goad, M.E. (2000) Neoplastic mass in an experimental Mongolian gerbil.

Ringler, D.H., Lay, D.M., & Abrams, G.D. (1972) Spontaneous neoplasms in aging gerbillinae. Laboratory Animal Science 22:407-414.

Rowe, S.E., Simmons, J.L. Ringler, D.H., & Lay, D.M. (1974) Spon­taneous neoplasms in aging Gerbillinae. Veterinary Pathology 11:38-51.

Shumaker, R.C., Paik, S.K., & Houser, W.D. (1974) Tumors in Gerbillinae: a literature review and report of a case. Laboratory Animal Science 24:688-690.

Su, Y.C., Wang, M.H., & Wu, M.F. (2001) Cutaneous B cell lym­phoma in a Mongolian gerbil (Meriones unguiculatus). Contem­porary Topics in Laboratory Animal Science 40(5):53- 56.

Vincent, A.L. & Ash, L.R. (1978) Further observations on sponta­neous neoplasms in the Mongolian gerbil (Meriones unguicula- tus). Laboratory Animal Science 28:297-300.

Vincent, A.L., Porter, D.D., & Ash, L.R. (1975) Spontaneous lesions and parasites of the Mongolian gerbil, Meriones unguiculatus. Laboratory Animal Science 25:711-722.

Vincent, A.L., Rodrick, G.E., & Sodeman, W.A., Jr. (1979) The pathology of the Mongolian gerbil (Meriones unguiculatus): a review. Laboratory Animal Science 29:645-651.