INFLAMMATORY LEIOMYOSARCOMA - A MORPHOLOGICAL SUBGROUP WITHIN THE HETEROGENEOUS FAMILY OF SO-CALLED INFLAMMATORY MALIGNANT FIBROUS HISTIOCYTOMA

Twelve cases of inflammatory leiomyosarcoma are presented. These tumou rs arose in the deep soft tissues of the trunk and proximal limbs, The age of the patients ranged from 13-53 years (median 36 years); there was an approximately equal sex ratio. Follow-up data was available for nine patients (mean duration 3.3 years); local recurrence occurred in three and lung metastases in one. Lesions were spindle cell neoplasms with fascicular areas which occupied between 5% and 80% of the tumour . Areas with a distinct storiform pattern were also seen in 10 cases, A prominent inflammatory cell component was evident in all tumours, of ten masking the neoplastic spindle cells, Histiocytes were identified in all cases, with aggregates of xanthoma cells seen in eight tumours. In 10 cases there was also a dense lymphoid infiltrate and in two a m arked polymorphonuclear leukocyte infiltrate was evident, Immunohistoc hemistry showed in all tumours that the spindle cells stained positive ly for myogenic markers (8 of 12 positive for desmin, 10 of 12 for alp ha smooth muscle actin and 11 of 12 for HHF-35). CD68 was expressed by the histiocytic infiltrates, Many of these tumours were diagnosed ini tially as inflammatory malignant fibrous histiocytoma. We provide evid ence that at least one subset of neoplasms, which would have been form erly classified under this rubric, in fact show smooth muscle differen tiaton. Further studies are required to investigate the possibility th at other tumour types or lines of differentiation may be present withi n the category of so-called inflammatory malignant fibrous histiocytom a.