Haemosiderotic fibrolipomatous tumors or haemosiderotic fibrohistiocytic lipomatous lesions are locally aggressive soft tissue tumors of uncertain differentiation.
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Epidemiology
Haemosiderotic fibrolipomatous tumors are rare with an estimated incidence of less than 0.2% of all benign lipomatous lesions. They have been described in all ages, but are predominantly seen in women in their 5th and 6th decades of life 1-3.
Diagnosis
Haemosiderotic fibrolipomatous tumors are diagnosed based on typical histological and molecular pathological features.
Diagnostic criteria
Diagnostic criteria according to the WHO classification of soft tissue tumors (blue book) 1:
- mature adipose tissue intermingled with bland hemosiderin-containing spindle cells and macrophages
The following criterion is desirable:
- TGFBR3 and/or OGA rearrangement
Clinical presentation
Clinically the tumors commonly manifest as a slow-growing subcutaneous mass sometimes associated with pain. Less often they occur in the deep soft tissues 1.
Pathology
Haemosiderotic fibrolipomatous tumors are unencapsulated neoplasms consisting of adipocytes and spindle cells with intracytoplasmatic hemosiderin inclusions 1.
Etiology
The etiology of haemosiderotic fibrolipomatous tumors is unknown 1.
Location
Haemosiderotic fibrolipomatous tumors are predominantly found in the following locations 1:
- dorsum of the foot and ankle region
- hands
- calf and thighs
- cheeks
Macroscopic appearance
Macroscopically haemosiderotic fibrolipomatous tumors are poorly delineated friable lesions with a dark yellow to brown color. They can be quite sizable on detection with an average of 7-8 cm 1-3.
Microscopic appearance
Microscopically haemosiderotic fibrolipomatous tumors consist of lobules of mature adipocytic cells mixed with fascicles of hemosiderin-containing fibroblastic spindle cells and hemosiderin-laden macrophages and giant cells. Beyond that, there are sometimes features resembling pleomorphic hyalinizing angiectatic tumors as ectatic partially thrombosed vessels with perivascular hyalinisation. There is usually no necrosis and a low mitotic activity 1,3.
Immunophenotype
On immunohistochemistry stains, haemosiderotic fibrolipomatous tumors usually express CD34 and calponin 1.
Genetics
Similar to pleomorphic hyalinizing angiectatic tumors of soft parts, haemosiderotic fibrolipomatous tumors are associated with rearrangements of the TGFBR3 and/or OGA genes 1.
Radiographic features
MRI
On MRI haemosiderotic fibrolipomatous tumors have been described as an ill-defined complex predominantly fat-intense mass with intermixed lipomatous and fibrous elements and with hemosiderin deposits 1-4, often displaying a blooming phenomenon on gradient echo sequences 5.
Signal characteristics
- T1: heterogeneous in up to 2/3 iso- to hypointense to muscle 5
- T2: heterogeneously hyperintense
- STIR/PDFS: heterogeneously hypointense
- T1C+ (Gd): heterogeneous enhancement
Radiology report
The radiological report should include a description of the following:
- form, location and size
- tumor margins and transition zone
- relations to the muscular fascia
- relation to adjacent neurovascular structures
- relations to bones
Treatment and prognosis
Treatment includes surgical excision. Local recurrence occurs in about 30-50% of the resected lesions in particular upon incomplete excision. The tumor itself does not metastasize but transformations to myxoid sarcoma have been described 1-3.
History and etymology
Haemosiderotic fibrolipomatous tumors have been first reported by the American pathologists, Cristina Marshall-Taylor and Julie C. Fanburg-Smith in 2000 2,3,6.
Differential diagnosis
Tumors or conditions which can mimic the presentation and/or appearance of haemosiderotic fibrolipomatous tumors include lipomas, atypical lipomatous tumors and pleomorphic hyalinizing angiectatic tumors of soft parts 2,3.