Diagnosi ultrastrutturale di miopericitoma cutaneo nel cane

In humans, myopericytoma is a neoplastic entity characterized histologically by a concentric perivascularproliferation of neoplastic cells with transitional myoid differentiation. Myopericytoma has been describedin dogs and Fischer rats, however their ultrastructural characterization is missing in dogs. An 11-year-oldRottweiler had a subcutaneous mass in the left anterior limb. Histology was characterized by interlacingbundles of spindle cells, perivascular whorls, staghorn growth, and occasional multinucleated neoplasticcells. The tumour was calponin (> 75%), myosin, vimentin, CD34 (50-75%), pan-actin, smooth muscleactin, desmin, laminin (5-25%) positive and smoothelin, h-caldesmon, CD18, FVIII, CD31, GFAP, S100,NSE, cytokeratin, Melan-A, 3G5 negative. Histology and immunohistochemistry were consistent with aperivascular tumour (myopericytoma or angioleiomyoma). On electron microscopy neoplastic cells werespindle, with active reticulated nucleolus, complex cytoplasmic processes, variably developed externallamina, moderate number of pinocytic vesicles, rare focal subplasmalemmal densities, rare myofilaments,vimentin bundles, dilated rough endoplasmic reticulum, variable number of mitochondria, occasionally ringshaped,and rare lipid droplets. Ultrastructural analysis was diagnostic for cutaneous myopericytoma andallowed the differential diagnosis with other neoplasms characterized by perivascular concentric growth.[...]