Giant cell tumor of soft tissue
Giant cell tumors of soft tissue are fibrohistiocytic neoplasms of uncertain behavior that show morphological similarities to giant cell tumor of bone but are not related genetically.
Terminology
Giant cell tumor of low malignant potential is a term that should not be used any longer .
Epidemiology
Giant cell tumors of soft tissue are very rare and seen in a wide range of age with a peak incidence in the 5th decade. There is no predilection for gender or ethnicity .
Clinical presentation
The tumors often present as indolent slowly-growing mass .
Pathology
Giant cell tumors of soft tissue are multinodular soft tissue neoplasms characterized by mononuclear histiocytoid cells and osteoclast-like giant cells frequently with metaplastic bone formation .
Etiology
The etiology of giant cell tumor of soft tissue is unknown .
Location
About 70% of the tumors affect the subcutaneous fatty tissue and the skin, approximately 30% involve the deep soft tissues underneath the superficial fascia. Most giant cell tumors of soft tissue are located in the upper and lower limbs and a lesser number is situated in the trunk or the head and neck area .
Macroscopic appearance
Macroscopically giant cell tumors of soft tissue are solid well-demarcated nodular lesions with a brown-reddish to a grey color. Many tumors feature peripheral gritty regions of mineralized bone .
Microscopic appearance
The microscopic spectrum of giant cell tumors of soft tissue includes the following features :
- multinodular architecture with cellular nodules separated by sclerotic septa with sideritic components
- histiocytoid mononuclear cells with interposed multinucleated osteoclast-like giant cells
- stroma with abundant vascularity
- no nuclear pleomorphism
- rare necrosis
- osseous metaplasia in about half of the tumors
- commonly stromal hemorrhage and regressive change
Immunohistochemistry
Immunohistochemistry stains might express vimentin, CD68, smooth muscle actin or alkaline phosphatase. However, they do not seem to be particularly helpful .
Genetics
Different to giant cell tumor of bone mutations of the H3-3A (H3F3A) gene are typically absent .
Radiographic features
There are only a few reports where imaging features of giant cell tumors of soft tissue have been described, they include the following :
- cystic lesions with internal nodules or debris
- possible daughter cysts
- adjacent nondescript soft tissue changes
Ultrasound
Ultrasound appearances have been described as cystic with an internal hyperechoic solid nodule possibly associated with daughter cysts and internal debris .
MRI
Cystic lesions with fluid-fluid levels and differences in signal intensity as well as internal or adjacent solid portions or nodules have been reported as imaging features. Cyst wall and solid portions of the tumors have been described with the following signal characteristics :
- T1: low to intermediate signal intensity
- T2: low to intermediate signal intensity
- T2FS/STIR: high signal
- T1 C+ (Gd): avid enhancement of cyst wall and solid portions
Radiology report
The radiological report should include a description of the following points:
- form, location and size
- tumor margins
- relation to the muscular fascia
- relationship to bones, tendons and joints
- relationship to local nerves and vessels
Treatment and prognosis
The common management is surgical excision. Local recurrence is uncommon and occurs in about 12%. Metastases are very rare .
History and etymology
Giant cell tumor of soft tissue was apparently first reported in 1972 by R Salm and HA Sissons .
Differential diagnosis
The differential diagnosis of giant cell tumors of soft tissue are the following :
