Cardiac rhabdomyoma in a slaughtered heifer
Ramírez-Romero, RafaelRamírez-Hernández, Cecilia
During routine inspection of a slaughtered heifer from a feedlot, the veterinarian in charge condemned the heartdue to a lesion on the endocardium. Histopathology and immunohistochemistry showed that the lesion was composed bycardiac tissues at different degree of differentiation, disordered and out of proportion. The most conspicuous was adispersed population of large, vacuolated and PAS positive cells, enmeshed in excessive fibrous connective tissue. Thesecells, identified as spider cells, resulted markedly positive for desmin, and negative for vimentin, smooth muscle α-actin andmyogenin factor 4. An extensive infiltration by fibro-fatty tissue was other abnormal component of the lesion. Furthermore,abnormal cardiomyoblasts forming tortuous bundles were also recognized. Nonetheless, these cells showed distinctivestriations and even intercalated discs. Some of this abnormal cardiac myoblasts resulted markedly positive for desmin andisolated strands also were positive for smooth muscle α-actin, but negative for myogenin factor 4 and vimentin. Based onthe pathognomonic spider cells and immunoreactivity, the lesion was classified as a cardiac rhabdomyoma. For some, thecardiac rhabdomyomas are not true neoplasms but congenital hamartomas in heart. However, principal component incardiac hamartomas in animals is an abnormal vascular pattern completely different from the lesion herein presented. Basedon the diverse tissue components, their immature and distorted image and, positive results for immunomarkers of earlymyoblast differentiation as well as terminal cardiomyocyte characteristics, dysplasia must be considered as the commondenominator in development of cardiac rhabdomyomas with tissue heterogeneity.(AU)
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