Clear Cell Sarcoma of Kidney : Classic Pattern
Classic Morphologic Pattern in Clear Cell Sarcoma of Kidney: The most common is the classic pattern which is present, at least focally, in >90% of cases. It consists of nests, columns, palisades or cords of small uniform polygonal to ovoid to spindle cells, separated by regularly spaced vascular channels. The cellular cords are 4 to 10 cells thick. The vascular channels range from delicate, arborizing capillaries with a "chicken-wire" appearance (similar to those seen in myxoid liposarcomas) to blood vessels encased in thick fibrocollagenous bands. In some cases, the vascular spaces are dilated and have staghorn, hemangiopericytomatous configuration. The tumor cells have pale-staining or clear cytoplasm, indistinct cell borders, uniform round or oval nuclei with evenly dispersed chromatin (i.e. without coarse condensations) and inconspicuous or punctate nucleoli. Many nuclei appear empty or optically clear (Orphan Annie nuclei) due to fixation-artifact. Mitotic activity is low. The background stroma may be myxoid, fibrotic or hyalinized. Anaplastic nuclei are seen in about 3% of cases.