Histopathological characteristics of luteal hypertrophy induced by ethylene glycol monomethyl ether with a comparison to normal luteal morphology in rats.

Ethylene glycol monomethyl ether (EGME) is a known reproductive toxicant that induces luteal hypertrophy in rat ovaries. In this study, we characterized the histopathological features of corpora lutea (CL) from EGME-treated rats and compared them with normal CL formation and regression. Normally cycling female Sprague-Dawley rats were treated with 5-bromo-2'-deoxyuridine (BrdU) intraperitoneally on the morning of estrus and their ovaries were examined 1 (metestrus), 4 (estrus), 8 (estrus), or 12 (estrus) days later to observe the transition of BrdU-labeled cells within in the CL. CL at each time point of estrus stage were classified into 4 types: Type I (newly formed CL), Type II (mature CL), Type III (regressing CL), and Type IV (residual CL). CL almost fully regressed within 4 estrus cycles. In contrast, in female rats given EGME orally (30, 100, or 300 mg/kg for 2 or 4 weeks), luteal cells were hypertrophic with abundant cytoplasm. Although the size of CL varied, all CL in EGME-treated rats had histological features similar to Type II CL, but they were more hypertrophic with less apoptosis. These results suggest that EGME has a luteal hypertrophic effect on all CL phases, including regression.

Primary neuroblastoma in the skin of an adult shih tzu dog.

A subcutaneous mass arising in the right gluteal area of an 11-year-old female shih tzu dog was surgically excised. Histologically, the mass was composed of small round or ovoid neoplastic cells that were arranged in nests of various sizes. The neoplastic cells generally had hyperchromatic nuclei and scanty eosinophilic cytoplasm, and were surrounded by a pale pink fibrillar area. Immunohistochemically, the neoplastic cells were positive for vimentin, S-100 protein, neurone-specific enolase and synaptophysin, but negative for cytokeratin, neurofilament protein, glial fibrillary acidic protein and chromogranin A. On ultrastructural observation, aggregates of thin cytoplasmic processes were frequently seen among the neoplastic cells. Based on these features, the tumour was diagnosed as a neuroblastoma. To the authors' knowledge, this is the first description of a neuroblastoma originating from the skin in an adult dog.