Giant cell tumor of soft tissue

Last revised by Joachim Feger on 17 Sep 2022

Giant cell tumors of soft tissue are fibrohistiocytic neoplasms of uncertain behavior that show morphological similarities to giant cell tumors of bone but are not related genetically.

Giant cell tumor of low malignant potential is a term that should not be used any longer 1.

Giant cell tumors of soft tissue are very rare and seen in a wide range of ages with a peak incidence in the 5th decade. There is no predilection for gender or ethnicity 1,2.

The diagnosis of giant cell tumors of soft tissue is established histologically, the location of the tumor is an important clue to diagnosis 1.

Diagnostic criteria according to the WHO classification of soft tissue and bone tumors (5th edition) 1:

  • multinodular tumor occurring in the superficial soft tissues
  • a population of osteoclast-like giant cells and histiocytoid mononuclear cells
  • frequent metaplastic bone formation and hemosiderin deposition

The tumors often present as indolent slowly-growing mass 1.

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 1-3.

The etiology of giant cell tumors of soft tissue is unknown 1.

About 70% of the tumors affect the subcutaneous fatty tissue and the skin, and 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 are situated in the trunk or the head and neck area 1

Macroscopically giant cell tumors of soft tissue are solid well-demarcated nodular lesions with a brown-reddish to grey color. Many tumors feature peripheral gritty regions of mineralized bone 1-3

The microscopic spectrum of giant cell tumors of soft tissue includes the following features 1-3:

  • 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 stains might express vimentin, CD68, smooth muscle actin or alkaline phosphatase. However, they do not seem to be particularly helpful 1.

Different to giant cell tumors of bone mutations of the H3-3A (H3F3A) gene are typically absent 1,2.

There are only a few reports where imaging features of giant cell tumors of soft tissue have been described, they include the following 3,4:

  • cystic lesions with internal nodules or debris
  • possible daughter cysts
  • adjacent nondescript soft tissue changes

Ultrasound appearances have been described as cystic with an internal hyperechoic solid nodule possibly associated with daughter cysts and internal debris 3,4.

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 3,4:

  • 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 

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

The common management is surgical excision. Local recurrence is uncommon and occurs in about 12%. Metastases are very rare 1.

Giant cell tumor of soft tissue was first reported in 1972 by the British pathologist R Salm and orthopedic surgeon HA Sissons 3,5.

The differential diagnosis of giant cell tumors of soft tissue are the following 3,4:

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