The first edition of Histological Typing of Soft Tissue Tumours, pub-
lished in 1969, represented a major step in the standardization of
nomen- clature in this specialty area. Accompanied by a glass slide set
of more than a hundred common and exotic tumours, this book resulted in
the rapid assimilation of a universal set of guidelines and diagnostic
defini- tions by pathologists in many countries. In the intervening two
decades numerous changes have occurred, and our committee has been chal-
lenged by the desire to incorporate new and exciting findings from the
areas of immunohistochemistry and molecular biology into the classifi-
cation with the need to develop a simple reproducible classification for
practising pathologists. The current system, while based principally on
standard microscopic observations, acknowledges and cites the use of di-
agnostically valuable ancillary techniques. Changes in the
Classification Although the original classification utilized the concept
of "histogene- sis" or tissue of origin in defining tumours, we have
departed from that point of view, acknowledging the impossibility of
determining histogen- esis by morphologic means alone. This
classification is based on the "line of differentiation", or stated
simply, by comparing tumours to the nor- mal cell they most closely
resemble without necessarily implying origin therefrom. As in the old
classification we have interpreted the term "tu- mours" in the broadest
sense of the word and have, therefore, included neoplastic and
non-neoplastic conditions.
