Summary
A spontaneous tumor originated in the dorsal muscles of the proximal portion of the tail of a 2.5-year-old axolotl (Siredon mexicanum). Histologically, the tumor consisted of tissues derived from ectoderm, mesoderm, and endoderm. Its most significant cells were epithelial, partly organized in the form of gland-like structures. The neoplastic glandular epithelium was arranged mostly in solid sheets or cords resting on a thin basement membrane; this tissue did not resemble any of the well-developed or differentiated epithelium or glandular tissue known to occur in the axolotl. The cells contained scanty cytoplasm with abundant basophilic material. Their nuclei were large and hyperchromatic and had one or two prominent nucleoli. Only these cells underwent mitosis, which was extensive in some areas. A second common tissue most likely resulted from differentiation and gradual degeneration of the epithelial tumor tissue, producing rounded pieces of compact tissues with a comparatively small number of nuclei and gradually increasing amounts of intercellular material. The nuclei became pycnotic and fewer in number. The tumor also contained loose, compact, and embryonic connective tissues. In septa composed of connective tissue, isolated striated muscle was found. In some areas there were neuroepithelial structures and abnormal cartilage. There were few blood vessels, many blood sinuses, and many blood cells in various stages of development.
This tumor was evidently a spontaneous teratoma.
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