[Hyalinizing spindle cell tumor with giant rosettes. Case report with immunohistochemical characterization]

This is a case of a 46-years-old male patient with a long-standing history of lower abdominal complaints. A 6-cm measuring tumor was detected by CT and subsequently surgically removed. Classification of this tumor and prognosis was problematic in frozen section and paraffin-embedded material, including immunohistochemical studies. The immunohistochemical findings were compatible with myofibroblastic differentiation of tumor cells. The histologic pattern resembled a "hyalinizing spindle cell tumor with giant rosettes" as recently published. Even if there were certain discrepancies in the immunohistochemical findings in our case, we also recommended treating this tumor as a low-grade sarcoma. The malignancy was also supported by marked proliferative activity demonstrated by MIB 1/KI 67 expression in numerous tumor cells. Finally, it has not yet been determined whether the hyalinizing spindle cell tumor is a pattern associated with a certain cellular differentiation or a pattern common to several mesenchymal tumor types.