Abstract

Soft tissue tumor is defined as a tumor occurring in voluntary muscles, fat, fibrous tissue, along with the vessels serving these tissue and peripheral nervous system. It is difficult to make a diagnosis by conventional microscopic observation because of their pleuripotentiality and similar growth characteristics. Although their morphological findings of tumors are similar to one another, their clinical courses, treatment and prognosis are different. So early, correct diagnosis and proper treatment are neccessary. The present study is aimed to evaluate a value of immunoperoxidase staining to make definite diagnosis of soft tissue tumors and its application to surgical pathology. The material consisted of 106 cases of fibrohistiocytic tumors and malignant soft tissue tumors which are morphologically similar to malignant fibrohistiocytic tumors for 5 years period lasting from 1980 to 1984 at the Department of Pathology, Yonsei University College of Medicine. After the classificationof fibrohistiocytic tumors by the Enzinger (1983), clinical finndings were reviewed and peroxidase antiperoxidase(PAP) method with alpha1-antichymotrypsin was done in 15 cases of all fibrohistiocytic tumors. Other soft tissue tumors which were difficult to differentiate from MFH by light microscopic observation were liposarcoma, rhabdomyosarcoma, fibrosarcoma and malignant schwannoma. These 21 cases of tumors including MFH were stained with PAP method for alpha1-antichymotrypsin, S-100 protein and myoglobin.
Results
obtained were as follows: 1) The cases on study consisted of 19 cases of malignant fibrous histiocytoma, 2 dermatofibrosarcoma protuberans, 45 fibrohistiocytic tumors and 11 other benign fibrohistiocytic tumors. 2) The male to female ratio was 1 : 1.8 in benign and intermediate group of fibrohistiocytic tumor, but 2.2 : 1 in malignant histiocytic tumor. 3) Most cases of benign fibrohistiocytic tumors were occurred in 4th and 5th decade of life. Intermediate and malignant fibrohistiocytic tumors were mostly found in late adult life and their mean age was 43.6 year. 4) The most common sites were trunk and both extrimities in benign fibrohistiocytic tumors(88.9%), but head, neck and lower extremities in MFH (78.9%). Two cases of dermatofibrosarcoma protuberans were occurred in turnk and upper extremity. 5) The PAP stain for alpha1-antichymotrypsin was done in 15 cases of 77 fibrohistiocytic tumors which included MFH, dermatofibrosarcoma protuberans, xanthoma, xanthofibroma, dermatofibroma showed variable degree of positivity to alpha1-antichymotrypsin. The positivity of alpha1-antichymotrypsin revealed no significant difference according to differentiation of the tumors, such as benign, intermediate and malignant. 6) The PAP stain for alpha1-antichymotrypsin revealed diffuse positivity in all cases of MFH and also in a case of malignant schwannoma, fibrosarcoma, liposarcoma and rhabdomyosarcoma, but myoglobin and S-100 protein were negative. In three cases of leiomyosarcoma, two of rhabdomyosarcoma and three of malignant schwannoma, alpha1-antichymotrypsin, S-100 protein and myoglobin were negative, although a few positive tumor cells were present, which may the considered as metatypci differentiation. Another possibility of this discordance was loss of antigenicity by improper procedure of paraffin embedding and poor differentiation of tumor cells. In summary, PAP method for specific tumor marker is important for proper diagnosis of soft tissue tumors, and application to surgical pathology.