ABSTRACT. A case of mast cell sarcoma in a 5-month-old Holstein female calf is described. Macroscopically, enlargement of the spleen, lymph nodes, tonsils and kidneys was noted, and there were tumor masses in the neck region and on the pleura and peritoneum. The pericardium and uterine and ureter walls were also involved by tumor. Most neoplastic cells had eosinophilic granules, which were metachromatic and positive for naphthol AS-D chloroacetate esterase and tryptase, whereas smaller numbers of cells were positive for factor VIII-related antigen, a marker of megakaryocytes. Some of the predominant type of these tumor cells were found within the epithelia of the lungs, tonsils, gastrointestinal tract, liver, ureters, urinary bladder and uterus. Their normal counterparts were considered to be globule leukocytes. KEY WORDS: cattle, epitheliotropism, globule leukocyte, mast cell sarcoma.doi: 10.1292/jvms.12-0236; J. Vet. Med. Sci. 74(12): 1643-1646, 2012 Mast cell tumors in dogs are the most frequent malignant or potentially malignant tumor of the skin [7]. In humans, systemic mastocytosis is a disease caused by a neoplastic proliferation of mast cells. Most cases have the skin lesions of urticaria pigmentosa, and the majority of these have a relatively benign course [2]. In contrast, cases without skin lesions have a worse prognosis and may progress to transformation into mast cell leukemia or, more commonly, acute myeloblastic leukemia [9]. Highly malignant mast cell disorders such as mast cell leukemia and mast cell sarcoma are cytologically distinct from indolent systemic mastocytosis [2], and are not always associated with the mastocytosis [3].In cattle, mastocytoma is a benign or low malignancy neoplasm of mast cell origin, occurring chiefly in the skin [8]. Although multiple skin lesions or metastases in visceral organs are not infrequent, cutaneous mastocytomas are characterized by rare or absent mitotic figures [8]. Leukemias of the mast cell lineage [19] or with both mastocytic and megakaryocytic differentiation [10] have been observed in cattle. Here, we report, in a calf, a mast cell sarcoma that possessed mast cell features such as metachromasia and tryptase positivity, but also factor VIII-related antigen expression in a minority of cells.A 5-month-old Holstein female calf exhibited enlargement of the superficial lymph nodes, emaciation, growth retardation, rough hair coat and a rectal temperature of 40.5°C. The next day, hematological values were as follows: hematocrit, 17%; white blood cell count, 8,560 cells/ µl with 2% neutrophils, 43% lymphocytes, 1% monocytes and 54% atypical cells with nuclear irregularity and/or coarse azurophilic granules in the cytoplasm. Antibodies to bovine leukosis virus (BLV) were not detected by the agar gel immunodiffusion test. A clinical diagnosis of calf-form leukosis was made, and euthanasia was performed seven days after the initial examination.At necropsy, the superficial lymph nodes were highly to moderately enlarged, and were grayish white and homogeneous on c...

The histology and immunohistochemistry of pleomorphic and conventional epithelioid mesotheliomas were examined. The former was detected in two young calves aged 2 and 4 months and was characterized by pleomorphic and atypical cells with decreased expression of cytokeratin 7 (CK7). In contrast, the latter was found in a 31-month-old heifer, consisting of tumor cells uniform in size and shape with CK7 expression in nearly all cells. Production of collagen by tumor cells was demonstrated in both histological types, and was considered to be characteristic of bovine epithelioid mesothelioma. Pleomorphic mesothelioma is far more pleomorphic and mitotically active than conventional mesothelioma, and its normal counterpart may be immature mesothelial cells with high proliferation potential, which exist in fetal life and early calfhood.

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