Spontaneous case of subcutaneous fibrosarcoma in an aged albino rat- A case report

A 24-months-old male Albino rat was presented with a grayish-white subcutaneous mass on the right side of abdomen for last four months. On cytology, the neoplastic cells showed moderate pleomorphism, round to elongated nuclei with 1–2 variably sized nucleoli and moderate amount of bluish cytoplasm. Microscopically, the mass was composed of moderately pleomorphic cells with a basophilic cytoplasm, tapering elongated dark nuclei arranged in a whorled pattern, and the presence of numerous thin-walled blood vessels. The mitotic figures were rarely seen. The interstitial space in the tumorous mass was composed of abundant collagen, confirmed by Masson’s trichrome stain. Argyrophilic nucleolar organizer region (AgNOR) staining was employed and the mean AgNORs count was found to be 4.89±1.73. Immunohistochemistry showed a mild positive immune labelling for the p53 marker in the tumor cells. Conclusively, the subcutaneous mass in an aged Albino rat was diagnosed as fibrosarcoma.