Multicentric Fibromyxoid Peripheral Nerve Sheath Tumor (Multicentric Schwannoma) in a Dromedary Camel (Camelus dromedarius)

Abstract

During postslaughter inspection of a 4-year-old male dromedary camel (Camelus dromedarius), numerous small nodules to large masses up to 4 cm in diameter were found on the serosal surfaces of forestomachs, large intestines, mesentery, liver, and spleen. Grossly, the masses were discrete, round, smooth, and white to gray that bulged from the serosal layer. Cut surfaces of the masses were discrete, round, white, and relatively homogeneous without any necrotic foci. Histopathologically, the masses were encapsulated and composed of a mixture of round and spindle-shaped cells in loose whorls of neoplastic cells with small elongated hyperchromatic wavy nuclei and a small amount of pale eosinophilic, poorly defined cytoplasm. Masson's trichrome staining showed mild amounts of collagen fibers forming an irregular, loose stroma. In immunohistochemistry, immunoreactivity for the Schwann cell marker (S100) was diffusely positive in the neoplastic cells. The immunoreactivity for CK, c-kit, and CD34 were negative. Ultrastructural examination confirmed the tumor was entirely formed of neoplastic Schwann cells. On the basis of the histopathological, immunohistochemical, and ultrastructural findings, the tumors were diagnosed as multicentric fibromyxoid peripheral nerve sheath tumor (multicentric schwannoma). This tumor has not been previously recorded in camel worldwide.