Case history: A 3 yr-old, female, Cocker Spaniel, was submitted to necropsy after being sacrificed. The dog presented a huge (10 x 15 x 22 cm) tumorous mass that occupied all mammary glands. Selected tissues (brain, lung, liver, mammary gland, and kidney) were fixed in 10% formalin solution and processed for routine histopathology evaluation.

Discussion: At necropsy a firm tumorous ulcerated mass occupied all the mammary glands; sectioned surface revealed pale-whitish, solid nodular zones that contained necrotic areas. Several rounded (0.5-1.5 cm) cream-whitish were observed within the pulmonary parenchyma. The liver was markedly hypertrophic and presented several cream nodular masses, which united to form a single tumor that demonstrated a cystic center; some of these nodes were umbilicated and protruded from the hepatic surface. Histopathology revealed the mammary tumor to be a solid adenocarcinoma, characterized by the proliferation of epithelial cells that formed a dense and extensive sheet of transformed cells; marked variation of cell size and shape, some mitosis and variation of nucleus-cytoplasm ration were evident. Similar masses were observed within the pulmonary parenchyma. The hepatic mass was diagnosed as a cholangiocarcinoma; being characterized by proliferation of bile duct epithelial cells forming nests of glandular-like structures surrounded by fibrous connective tissue. The occurrence of two different primary tumors in the same animal indicates that clinically independent primary tumors or metastatic diseases would have to be considered. The simultaneous appearance of different tumors is not well documented in domestic animals, these cases are more frequently described in human medicine, particularly in endocrine organs, where it is know as the multiple endocrine neoplasia (MEN) syndrome (Cock & MaClachlan, 1999). Recent research has suggested a possible molecular origin of multiple tumors in the same individual (Van Der Sijp, et al, 2002). A case with marked similarity to the MEN syndrome was described in the adrenal and thyroid glands of a horse (Cock & MaClachlan, 1999). Additionally, it was demonstrated that persons with squamous cell carcinoma of the head and neck often develop second carcinomas elsewhere in the upper aero-digestive tract; this has been related to the ability of a single progenitor cell to replicate, expand, and populate contiguous regions of the upper aero-digestive tract (Califano et al., 1999). However, no information has been found to fully explain this phenomenon in domestic animals.

References

1.  Cock, H. E. V.; Maclachlan, N. J. Simultaneous occurrence of multiple neoplasms and hyperplasias in the adrenal and thyroid gland of the horse resembling multiple endocrine neoplasia syndrome: case report and retrospective identification of additional cases. Veterinary Pathology, v. 36, p. 633-636, 1999.

2.  Van Der Sijp, J.R.M.; Van Meerbeeck, J.P.A.M.; Maat, A. P.W.M.; et al. Determination of the molecular relationship between multiple tumors within one patient is of clinical importance. Journal of Clinical Oncology, v. 20, p.105-1114, 2002.

3.  Califano, J.; Leong, P. L.; Koch, W.M.; et al. Second esophageal tumors in patients with head and neck squamous cell carcinoma: an assessment of clonal relationships. Clinical Cancer Research, v. 5, p.1862-1867, 1999.