Clear cell sarcoma of patellar tendon studied by electron microscopy

A case of clear-cell sarcoma of patellar tendon in a 31-year-old Japanese woman is reported, with an emphasis on its electron microscopic description. The chief fine structural findings were: 1. presence of 2 types of cells—large clear cell and small dark cell, with abundant glycogen contents, 2. basement membrane and pseudoacinal structures, 3. filopodia, and 4. electron-dense bodies in the cytoplasm. Some histogenetic relation to synovial tissue was suggested. It seems that the tumor might fall under the category of synovial sarcoma.