Haemosiderotic fibrolipomatous tumour (so-called haemosiderotic fibrohistiocytic lipomatous tumour): analysis of 13 new cases in support of a distinct entity.

AIMS: To describe 13 new cases of a rare soft tissue neoplasm currently known as haemosiderotic fibrohistiocytic lipomatous tumour (HFHLL) and to further its characterization. METHODS AND
RESULTS: Patients were eight females and five males, aged 8 months to 74 years. Lesions ranged in size from 10 to 130 mm (median 45). Twelve of 13 lesions were located in the ankle/foot region; one involved the hand. Grossly the lesions were fatty/gelatinous or lipoma-like. They were characterized by varying proportions of mature adipocytes and fibroblastic spindle cells, associated with haemosiderin pigment present predominantly in macrophages within the spindle cell component. Dissecting between adipocytic lobules were septa containing short spindle cells with streaming, swirling or honeycomb growth patterns. Most tumours contained scattered osteoclast-like giant cells. Mitoses were rare and only one case showed mild atypia. Immunohistochemistry in 10 cases showed 7/9 CD34+; all were negative for smooth muscle actin, CD68, S100 and desmin. Follow-up in nine cases ranging from 1 to 130 months (median 12) showed local recurrence in three but no metastasis.
CONCLUSIONS: So-called HFHLL, better termed haemosiderotic fibrolipomatous tumour, is a distinct lesion characterized by an admixture of fibroblastic spindle cells, mature adipocytes and haemosiderin pigmentation, shows a predilection for the distal extremities and quite often recurs locally.