Soft Tissue Sarcomas

Overview

Soft tissue sarcomas are malignant tumors arising from mesenchymal tissues such as:

• Muscle
• Fat
• Fibrous tissue
• Blood vessels
• Peripheral nerves

They may occur in:

• Extremities
• Pelvis
• Retroperitoneum
• Trunk
• Head and neck

Common histological types include:

• Liposarcoma
• Undifferentiated pleomorphic sarcoma
• Leiomyosarcoma
• Synovial sarcoma
• Fibrosarcoma
• Rhabdomyosarcoma

Most occur in adults between 40–70 years, except:

• Rhabdomyosarcoma: common in children
• Synovial sarcoma: common in adolescents and young adults

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General Clinical Features

Typical presentation:

• Painless enlarging soft tissue mass

Important features concerning for malignancy:

• Size >5 cm
• Deep location beneath fascia
• Rapid growth
• Recurrence after previous excision

Pain is less common, although:

• Synovial sarcoma may be painful

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Metastatic Pattern

Most common metastatic site:

• Lungs

Other sites:

• Bone
• Liver

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Imaging Characteristics

MRI Findings

MRI is the investigation of choice.

Typical findings:

• Heterogeneous T1 and T2 signals
• Necrosis
• Hemorrhage

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Special MRI Features

Myxoid Tumors

• Homogeneous appearance
• Hyperintense on T2
• Due to mucopolysaccharide content

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Well-Differentiated Liposarcoma

• Fat signal intensity
• Thick septations
• Nodular areas

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Synovial Sarcoma

May show:

• Calcifications
• Triple signal intensity on T2 imaging
  • Solid areas
  • Hemorrhagic areas
  • Cystic areas

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Common Locations

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Important Cytogenetic Translocations

Synovial Sarcoma

• t(X;18)
• Produces SYT-SSX fusion gene

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Myxoid / Round Cell Liposarcoma

• t(12;16)

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Alveolar Rhabdomyosarcoma

• t(2;13) or t(1;13)

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Immunohistochemistry

Most sarcomas are:

• Vimentin positive

Additional markers help identify lineage.

Examples:

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Liposarcoma

Overview

• Second most common soft tissue sarcoma
• Most common sarcoma in adults

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Subtypes

• Well differentiated
• Myxoid
• Round cell
• Pleomorphic
• Dedifferentiated

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Histology

Well Differentiated

• Resembles lipoma
• Lipoblasts present
• Thick atypical septa

Myxoid

• Myxoid matrix
• Arborizing capillaries

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Treatment

• Wide surgical excision
• Radiotherapy depending on margins and location

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Undifferentiated Pleomorphic Sarcoma

Previously called:

• Malignant fibrous histiocytoma

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Features

• High-grade sarcoma
• Pleomorphic spindle cells
• Deep soft tissue location
• Common in extremities and retroperitoneum

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Histology

• Storiform pattern
• Marked pleomorphism
• Necrosis common

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Treatment

• Wide excision
• Radiotherapy

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Fibrosarcoma

Features

• Malignant fibroblast tumor
• Usually deep soft tissue lesion

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Histology

Classic:

• Herringbone pattern

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Treatment

• Wide excision
• Radiotherapy

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Synovial Sarcoma

Overview

• Common near joints
• Rarely intra-articular
• Typically affects young adults

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Histological Types

Biphasic

• Spindle cells
• Epithelial cells

Monophasic

• Mainly spindle cells

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Imaging Features

• Calcification
• Cystic degeneration
• Triple signal intensity on MRI

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Treatment

• Wide excision
• Radiotherapy
• Chemotherapy often used in younger patients

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Rhabdomyosarcoma

Overview

• Most common malignant soft tissue tumor in children

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Subtypes

• Embryonal
• Alveolar
• Pleomorphic

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Histology

• Rhabdomyoblasts
• Cross striations may be seen

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Treatment

Multimodal treatment:

• Surgery
• Chemotherapy
• Radiotherapy

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Leiomyosarcoma

Overview

• Malignant smooth muscle tumor

Common sites:

• Retroperitoneum
• Deep soft tissues

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Histology

• Spindle cells
• Cigar-shaped nuclei
• Actin and desmin positive

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Treatment

• Wide surgical excision
• Radiotherapy

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Management Principles

Mainstay of Treatment

Wide Surgical Excision

Goals:

• Adequate margins
• Limb preservation
• Local control

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Radiotherapy

Used for:

• Local control
• High-grade tumors
• Large tumors
• Close margins

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Chemotherapy

Selective use in:

• Rhabdomyosarcoma
• Synovial sarcoma
• Metastatic disease

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Amputation

Reserved for:

• Unresectable tumors
• Extensive contamination
• Nonfunctional limb

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Prognostic Factors

Poor prognostic indicators:

• Large tumor size
• High grade
• Deep location
• Metastases
• Positive surgical margins

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Prognosis

• Five-year survival for nonmetastatic disease: approximately 60–65%
• Metastatic disease significantly worsens prognosis

Outcome depends on:

• Histological grade
• Tumor size
• Tumor location
• Completeness of surgical resection