Abstract

ABSTRACT: BACKGROUND: Soft tissue sarcoma (STS) represents a heterogeneous group of rare malignant tumors. Many diagnostic problems and difficulties are often encountered in the differential diagnosis of these tumors. The variety of appearance gives a wide range of tumor types and subtypes with a high discrepancy rate in tumor typing among pathologists. METHODS: This study was conducted at the Military Medical Academy (EGYPT) during the period from (1989-1990). The study aimed to reexamine a routinely processed H and E stained slides of cases previously diagnosed as STS by a group of pathologist and match the old and new diagnoses, with the application of some special stains; histochemical and immunohistochemical, then evaluate the results. Forty cases previously diagnosed as STS were reexamined and classified according to the criteria of Enzinger and Weiss. A descriptive or morphological classification was also used; as spindle, round, myxoid and pleomorphic STS. The results were compared to, and matched with the previous diagnoses. Histochemical stains used are, Picro Sirius red (PSR), Masson trichrome (MT), and Periodic-acid schiff stain (PAS). Myoglobin was used as immunohistochemical marker for the detection of cross-striated muscle cell differentiation by peroxidase antiperoxidase method (PAP). RESULTS: Agreement in diagnosis between the previous and the recent diagnosed STS was found to be 47.5%. For spindle cell malignant tumors the agreement was 58.8%, while for round cell malignant tumors was 33.3%. Agreement in diagnosis in mixed malignant soft tissue tumors was 62.5%. PSR and MT demonstrate the amount and distribution of collagen. MT also demonstrates muscle fibers. Using Myoglobin immunohistochemical marker in the previously diagnosed STS: one out of four cases diagnosed as Rhabdomyosarcomas gave a positive result, while two cases from the unsuspected group gave positive results. In the recently diagnosed tumors: all cases diagnosed as Rhabdomyosarcoma gave positive results, while from the unsuspected group one gave positive result. CONCLUSION: While the ordinary H and E stain will suffice to permit recognition of many of STS, it will not do so for all. Limitation of diagnosis of these tumors, especially the rare ones, to specialized centers or highly qualified pathologists is recommended. Histochemical stains are supportive rather than exclusive for the diagnosis of STS. Myoglobin immunohistochemical marker could be used to aid in the diagnosis of rhabdomyosarcomas. Definite diagnosis of many STS needs further special stains and/or electron microscopy and other sophisticated procedures