Twenty-five
synovial sarcomas were studied with a battery of
antibodies directed against
keratin and
epithelial membrane antigen (EMA). The
keratin antibody MNF 116 showed reactivity in 24
tumors. In addition, 22
tumors showed reactivity with the antibody
Keratin Wide Spectrum, 20 with the antibody
Keratin 56, 64, and 19 with CAM 5.2. Seventeen
tumors showed reactivity with EMA. The
keratin and EMA reactivity was present in cells lining obvious cleft-like structures in biphasic
tumors. In the spindle cell areas of both biphasic and monophasic fibrous
tumors, we found clusters of a few reacting cells apparently located around small clefts. In the synovioblastic
tumors, clusters of plump
tumor cells reactive for both the
keratins and EMA were present. In conclusion, we found that proper identification of epithelial differentiation in
synovial sarcomas is facilitated by an immunohistochemical application of anti-epithelial
antibodies. In most
tumors, there was immunoreactivity for the same type of
keratins as are normally identified in simple epithelia (the antibody CAM 5.2), but also for those found in stratified squamous epithelia (the antibody
Keratin 56, 64). The results indicate that screening for epithelial features on
paraffin sections in the various types of
synovial sarcoma, even the poorly differentiated synovioblastic
tumors, is improved if epithelial
antibodies with a broad spectrum of reactivity are chosen.