Accurate diagnosis of soft tissue tumors can be difficult and although some entities are readily diagnosed on routine histology, it is often prudent to perform additional studies in others. Selecting the appropriate test and correctly interpreting the results may be challenging to general pathologists, residents and fellows. We will use a case based approach encompassing lesions that are frequently seen in consultation. Examples of both "H&E alone" cases and lesions requiring molecular diagnostics will be offered, encompassing tips for avoiding common diagnostic errors and suggestions for dealing with needle biopsies. Discussion will include the use and utility of various tests as well as common pitfalls in interpretation, but will not address methodology or mechanisms of molecular analysis. This course is intended for residents and practicing pathologists. Multiple representative images of each case will be provided prior to the meeting on the USCAP website for review by pre-registrants. A syllabus will be available at the meeting and all participants will receive a CD containing the course material.

Topics to be addressed include: 1.) The many morphologic and immunohistochemical profiles of Ewing sarcoma. a) Pitfalls in immunohistochemical analysis b) Use of RT-PCR and FISH for translocation analysis. 2.) Vascular lesions: malignant or just ugly? a) Histologic features of malignant vascular tumors b) Angiosarcoma mimics 3.) Benign and low grade malignant spindle cell lesions: a logical approach a) Low grade fibroblastic sarcomas vs fibromatosis b) Fasciitis vs fibromatosis c) Mesenteric fibromatosis vs GIST 4.) Pseudosarcomas and pseudo-pseudosarcomas (i.e. sarcomas)

a) Reactive vs neoplastic b) Immunohistochemical adjuncts 5.) Pleomorphic undifferentiated sarcomas: the new MFH? a) What is pleomorphic and what does it mean? b) Pleomorphic sarcomas and sarcoma mimics 6.) Rhabdomyosarcoma: alveolar vs embryonal and does it matter? a) Muscle-specific markers in diagnosis and classification b) The role of translocation analysis in diagnosis and classification.

(New Course) This course may be used for CME credits or SAM's credits.