ABSTRACT
A 9-y-old male Boxer dog developed a mandibular skin tumor, which histologically had a locally invasive growth pattern composed of bilayered structures of inner eosinophilic cuboidal tumor cells and outer clear polygonal tumor cells with cytoplasm containing glycogen granules. Both cell populations gradually changed from low-grade morphologic features to highly anaplastic ones. Immunohistochemically, the eosinophilic tumor cells were positive for cytokeratin 8, a useful marker for luminal epithelial cells. In contrast, the clear tumor cells expressed several myoepithelial markers, including α-smooth muscle actin, p63, and cytokeratin 14. Based on these histologic and immunohistochemical characteristics, we diagnosed this apocrine sweat gland tumor as a carcinoma-and-malignant myoepithelioma with high-grade transformation of both luminal and myoepithelial cells. Our case may be a helpful reference for the histogenesis of carcinoma-and-malignant myoepithelioma, in which both the luminal epithelial and myoepithelial components are malignant.
Subject(s)
Bone Neoplasms , Carcinoma , Dog Diseases , Myoepithelioma , Sweat Gland Neoplasms , Animals , Dogs , Male , Biomarkers, Tumor , Bone Neoplasms/pathology , Bone Neoplasms/veterinary , Carcinoma/veterinary , Carcinoma/pathology , Dog Diseases/diagnosis , Dog Diseases/pathology , Epithelial Cells/pathology , Epithelium/pathology , Myoepithelioma/veterinary , Myoepithelioma/chemistry , Myoepithelioma/diagnosis , Sweat Gland Neoplasms/veterinary , Sweat Gland Neoplasms/pathologyABSTRACT
Cancer stem cells or tumor-initiating cells (TICs) are a small subpopulation of cells that have the capacity to self-renew, differentiate and initiate tumors. These cells may function in tumor initiation, aggression and recurrence. Whether spheres derived from canine rhabdomyosarcoma cells have stem cell-like properties is unclear. We induced sphere formation in the canine rhabdomyosarcoma cell lines, CMS-C and CMS-J, and characterized the spheres in vitro and in vivo. Sphere-forming cells were more resistant to vincristine, mitoxantrone and doxorubicin than adherent cells. Xenograft transplantation demonstrated that 1 × 103 sphere-forming cells derived from CMS-C were sufficient for tumor formation. The sphere assay showed that the sphere-forming cells were present in these tumors. These results suggest that the spheres derived from canine rhabdomyosarcoma cells may possess characteristics of TICs. This study provides the foundation for elucidating the contribution of TICs to rhabdomyosarcoma tumorigenesis.
