['In later years, several characteristic acquired chromosomal aberrations have been identified in mesenchymal tumors. Many of these aberrations, either alone or with histopathologic and clinical data, are useful in diagnosis. The cytogenetic profile of hemangiopericytomas has been poorly investigated.', 'Short-term cultures from four spindle cell tumors were cytogenetically analyzed.', 'Clonal acquired chromosome aberrations were found in three of the four tumors: inv(12) (q14q24) in a malignant hemangiopericytoma, a supernumerary der(3)t(3;12) (p21-23;q13-15) in a benign hemangiopericytoma, and t(6;12;19) (p21;q13;p13) in a spindle cell sarcoma that was histologically a malignant hemangiopericytoma or a synovial sarcoma. The fourth tumor, a malignant hemangiopericytoma, had a normal karyotype. The tumors with inv(12) and t(6;12;19) had subclones with trisomy 5 in addition to the structural changes.'] Do aberrations of chromosome segment 12q13-15 characterize a subgroup of hemangiopericytomas?