Classification of soft tissue sarcomas

Staging of soft tissue sarcomas

At present, there is no generally accepted staging of sarcoma in children. The most common are two classifications - the classification of TNM of the International Union Against Cancer and the classification of the International Rhabdomyosarcoma Study Group.

Histological classification of soft tissue sarcomas

Histologically, soft tissue sarcomas are extremely heterogeneous. Below are variants of malignant sarcomas and histogenetically corresponding to them types of tissues.

Soft-tissue sarcomas are also referred to as extra-osseous tumors from bone and cartilaginous tissue (extraossar osteosarcoma, myxoid and mesenchymal chondrosarcoma).

Morphologically, it is difficult to make differential diagnosis between non-bloomingosarcoma soft-tissue tumors. To clarify the diagnosis, use electron microscopy, immunohistochemical and cytogenetic studies.

The histological appearance of a tumor of soft tissues (with the exception of rhabdomyosarcoma) does not give a clear idea of the clinical course and prognosis of the disease. To determine the correlation between the histological variant and the tumor behavior, the POG multidisciplinary research group (Pediatric Oncology Group, USA) identified three variants of histological changes that could be used as forecasting factors in a prospective study. The degree of histological changes was determined by the indices of cellularity, cellular pleomorphism, mitotic activity, severity of necrosis and invasive tumor growth. It was shown that the tumors of the third group (degree III) in comparison with the first and second have a much worse prognosis.

Histological classification of soft tissue sarcomas

Fabrics	Types of tumors
Tumors of the striated muscle tissue	Rhabdomyosarcoma
Tumors of smooth muscle tissue	Leiomyosarcoma
Tumors of fibrous tissue	Infantile fibrosarcoma
	Dermatofibrosarcoma
Fibrogystiocytic tumors	Malignant fibrocytic histiocytoma
Tumors of adipose tissue	Liposarcoma
Vascular tumors	Angiosarcoma
	Lymphangiosarcoma
	Hemangioperetcitoma malignant
	Hemangiendothelioma
	Sarcoma Kaloshi
Tumors from the shells of peripheral nerves	Malignant Schwannoma
Tumors of different histogenesis	Malignant mesenchymoma
	Triton tumor
Tumors of unknown histogenesis	Synovial sarcoma
	Epithelioid sarcoma
	Alveolar soft tissue sarcoma
	Malignant melanoma of soft tissues
	Desmoplastic sarcoma from small round cells

Degree I.

• MIXOID and highly differentiated liposarcoma.
• Deeply located dermatofibrosarcoma.
• Well differentiated or infantile fibrosarcoma.
• Well-differentiated hemangiopericytoma.
• Well-differentiated malignant tumor of peripheral nerve membranes.
• Extraobdominal myxoid chondrosarcoma.
• Malignant fibrocytic histiocytoma.

Degree II.

• Soft-tissue sarcomas not included in the first and third groups. Signs of necrosis show less than 15% of the surface of the tumor, with microscopy with an increase of x40, fewer than five figures of mitosis are detected in 10 fields of vision, there is no atypia of the cell nuclei, the cellularity is low.

Degree III.

• Pleomorphic or round-celled liposarcoma.
• Mesenchymal chondrosarcoma.
• Extramural osteosarcoma.
• The Triton tumor.
• Alveolar soft tissue sarcoma.
• Synovial sarcoma.
• Epithelioid sarcoma.
• Cellular light sarcoma of soft tissues (malignant melanoma of soft tissues).
• Soft tissue sarcomas not included in the first group, showing signs of necrosis of more than 15% of the surface or more than 5 figures of mitosis with microscopy with an increase of x40.

Classification of TNM

Primary tumor.

• T ₁ - the tumor is limited by the organ (tissue) from which it occurs.
• T ₂ - the tumor goes beyond the body (tissue).
  • T _2a - a tumor in diameter less than or equal to 5 cm.
  • T _2b - tumor more than 5 cm in diameter.
• Regional lymph nodes.
  • N ₀ - regional lymph nodes are not affected.
  • N ₁ - regional lymph node involvement.
  • N _x - insufficient data to assess involvement of lymph nodes.
• Distant metastases.
  • M ₀ - distant metastases are absent.
  • M ₁ - there are distant metastases.

The prognostic significance of TNM factors is shown in a number of studies on the study of soft tissue sarcomas in children.

The classification of soft tissue sarcoma International Rhabdomyosarcoma Study Group, originally created for rhabdomyosarcoma, is currently used for all soft tissue tumors. It takes into account the volume of the residual tumor after the operation and the presence of metastases.

[1], [2], [3], [4], [5], [6]