Bone tumors with undetected or undetermined or unusual origin and the role of new diagnostic methods in their diagnosis detection and determination

Bone tumors are relatively common neoplasms composed of malignant, benign and intermediate varieties of which three groups are very important due to diagnostic, treatment and basic scientific aspects: 1- Tumors with unknown origin including giant cell tumor and Ewing’s sarcoma. 2- Unusual bone tumors including adipose, muscular and neural tissue tumors. 3- Bone metastases which are included in differential diagnosis of many primary bone tumors specially when their origin is not clinically detectable. The aim of this research is first to determine the role of new diagnostic methods specially immunohistochemistry staining in diagnosis and typing of these tumors and to compare the results with conventional microscopy for documenting more accurate diagnostis criteria, and second to compare their clinicoepidemiologic, radiologic and pathologic charecterstics with other world wide reports and third to achive more experience in routin microscopic diagnosis of these tumors. All tissue specimens archived in pathology department of Mashhad Emam Reza Hospital in last 30 years were evaluated. Among the 126670 filed specimens, 163 cases previously diagnosed as any one of these three groups were specified and elicited. Registered epidemioclinical and pathologic informations were gathered and organized in tables. Then microscopic slides were reviewed applying new diagnostic criteria, and if necessary further sections for conventional H/E and histochemical study were obtained and specially immunohistochemical assesment with appropriate markers was performed. From 163 elicited tissue specimens, 2 cases due to unrelated final histopathologic diagnoses and 5 cases because of their specification as soft tissue tumors, were rulled out. Tumors with unknown origin composed 61.5%, unusual bone tumors about 2% and bone metastases 36.5% of the documented studied tumors. In most cases the diagnostic, radiologic and pathologic charectristics were in correspondance with classical features of these tumors and other world wide reports. Merely 13% of the cases required immunohistochemical study for definite diagnosis, of which only in 4 cases the microscopic diagnosis changed. Conventional microscopic diagnostic method with carefull attention to clinical and radiologic findings is the main method for diagnosing these tumors, of course in few complicated cases complemental procedures such as immunohistochemistry is inevitable in diagnosing and determining accurated and true nature of these bone tumors.