Sarcoma

A sarcoma is a kind of tumor.

Soft tissue tumors are a very heterogeneous group of neoplasms classified according to their line of differentiation, according to the adult tissue they mimic. Classically, soft tissues are defined as non-epithelial extraskeletal tissue of the reticuloendothelial system, glia, and organ support tissues. They are tissues that connect, support or surround other tissues; and include muscles, tendons, fat, and blood vessels. By agreement, the peripheral nervous system is also included. Embryologically soft tissues derive from mesoderm, with some ectodermal contribution.

The term comes from a Greek word meaning growth of meat, but they are placed in a separate category due to their distinct microscopic, biological, and clinical characteristics, and are treated differently.

The vast majority are benign, with a high cure rate. The benign ones imitate the healthy tissue, and their autonomous growth is limited. They do not usually invade locally and rarely recur. The malignant or sarcomas are locally aggressive through invasion and/or destruction, they recur and can give distant metastases. However, not all sarcomas are equally aggressive or have the same ability to metastasize, so it is important to understand the term sarcoma according to the degree of differentiation of the neoplasia. A well-differentiated sarcoma is generally low grade, and a poorly differentiated one is usually high grade. Those with intermediate differentiation usually recur but rarely metastasize.

Epidemiology

Their frequency is difficult to determine. Benign forms of these neoplasms are much more common (benign/malignant ratio = 100/1). Sarcomas constitute approximately 1% of all malignant neoplasms, with an annual incidence of 6 per 100,000 inhabitants, although it varies according to age and histological type. There are no data indicating a change in its incidence or significant geographical differences in recent decades.

Etiology

In most cases, the underlying cause is unknown, although an association has been found with genetic or environmental factors, radiation, viral infections, or immune deficiencies. Most originate de novo and without apparent cause, although cases developed on scars or fractures, or close to surgical implants have been reported.

Chemical carcinogens

Cases of sarcoma have been reported after exposure to herbicides, chlorophenols and their metabolites used in the agricultural industry, although other studies have not found this association.

Radiation

The incidence of sarcomas associated with post-irradiation is highly variable depending on the study. The risk increases with the radiation dose, especially above 50 Gy, and the mean time between exposure and diagnosis is 10 years.

Viral infections and immunodeficiencies

The HHV8 virus plays a fundamental role in the development of Kaposi's sarcoma, and its clinical course depends on the patient's immune status. The Epstein-Barr virus (EBV) has also been associated with smooth muscle tumors in immunocompromised patients.

Genetic susceptibility

Several types of benign soft tissue tumors appear to have a familial or inherited basis, although they are rare reports and comprise a small number of tumors. The most common example is hereditary multiple lipomas, or desmoid tumors in Gardner syndrome.

Neurofibromatoses (types 1 and 2) are associated with multiple benign nerve tumors. In 2% of patients with NF type 1, malignant peripheral nerve sheath tumors appear on their benign variants.

Li-Fraumeni syndrome is a rare autosomal dominant disease caused by mutations in the TP53 tumor suppressor gene, of key importance in sarcomagenesis. Half of these patients have developed malignancies by age 30, one third of which are soft tissue and bone sarcomas.

Patients with a germline mutation in the Rb1 gene (retinoblastoma-associated) have a significantly increased risk of developing osteosarcoma.

Clinical picture

Of the benign neoplasms, 99% are superficial, and 95% are less than 5 cm in diameter. Sarcomas can appear in any location, but three quarters originate in the limbs, and 10% in the trunk and retroperitoneum, with a slight predominance in males. Like many other malignancies, sarcomas increase in incidence with age.

Those located deep (see retroperitoneum) can reach large sizes before giving symptoms, and one tenth of patients have distant metastases at the time of diagnosis.

Incidence varies by age and histologic subtype; Thus, embryonal rhabdomyosarcoma, for example, occurs almost exclusively in children, while synovial sarcoma is typical of young adults, and pleomorphic sarcoma, liposarcoma, or leiomyosarcoma are more frequent in advanced ages.

In general, it is considered that at least a third of these patients die from the tumor, the majority from lung metastases.

Most of them present as a painless mass with no functional limitation, even in large tumors. The innocent appearance at presentation and the low incidence of these neoplasms means that they are frequently underdiagnosed as benign tumors. That is why it is usually interpreted that superficial tumors greater than 5 cm in diameter and all deep-located tumors have a 10% risk of being a sarcoma.

Diagnosis

Radiology

Magnetic Resonance Imaging (MRI) is the technique of choice for detecting, characterizing, and staging these tumors, due to its ability to distinguish neoplastic tissue from healthy tissue, as well as to establish relations with the neurovascular bundles and nearby fascial planes. It also helps to plan surgical treatment, evaluate the response to chemotherapy and restage the neoplasia. It also makes it possible to obtain measurements and provides information on necrosis, hemorrhage, edema or cystification that may exist within the neoplasia.

Computerized Tomography (CT) can be used in some cases of thoracic and abdominal tumors to avoid the artifact caused by the tissue/air interface in MRI.

Positron Emission Tomography (PET) has the capacity to determine the biological activity of the tumor, and can be used to differentiate benign from poorly differentiated tumors, staging or evaluation of recurrences.

Anatomo-patological

Sampling is very appropriate to provide histological type, histological grade and malignancy, and thus predict the pattern of local growth or metastasis. However, for the definitive diagnosis, the complete neoplasm or at least a large part of it is required.

Incisional biopsy is indicated for most limb lesions, while excisional biopsy should be avoided in lesions larger than 2 cm, to prevent possible contamination of adjacent healthy tissue.

Although it can be used in deep-located lesions, its value will be limited in these cases, since it can be neoplasms with very heterogeneous areas of differentiation, and healthy areas could be sampled in highly necrotic tumors or vice versa.

Fine needle aspiration cytology (FNA) should be limited to health centers with a high rate of cases and with a well-integrated multidisciplinary team, so that clinical-radiological correlations and accumulated experience minimize the risk of number of possible diagnostic errors. Also, like incisional biopsy, sampling for this technique is limited.

Classification

According to your prognosis

The WHO recommends classifying soft tissue neoplasms into four groups according to their biological potential and within each histotypic group:

• BlessingsThey are those who do not recite. They are considered cured if the excision is complete. In extremely rare cases metastases of benign tumors of soft tissue have been reported. These are completely unpredictable behaviors based on histological aspect.

• Intermediate (locally aggressive): are tumors of frequent local recurrence, with local destructive growth pattern. They have no potential to metastatize, and require removal with wide surgical margins.

• Intermediate (rarely metastatizing): locally aggressive and with the ability to give occasional metastases (risk 2%), usually to lymph nodes and lung.

• Evil: locally aggressive, recurrent and able to give distant metastases (risk 20-100%). In some sarcomas the risk is lower, but as the histologic degree increases in recurrence, the probability of metastatizing is increasing.

According to histological type

The distribution of histological types has varied throughout history and continues to do so today. This is a consequence of changes in the definitions of histological subtypes. According to the latest WHO classification of soft tissue tumors (WHO, February 2013), these are classified as follows:

Adipocyte tumors

1.1. Blessings

• Lipoma
• Lipomatosis
• Lipomatosis of the nerve
• Lipopblastoma/lipoblastomatosis
• Angiolipoma
• Miolipoma
• Condroid lipoma
• Angiomiolipoma extra-renal
• Extra-adrenal myelolipoma
• Pleomorphic lipoma/Fusiform cell lipoma
• Hibernoma

1.2. Intermediate (locally aggressive)

• Atypical lipomatous tumor/well differentiated liposarcoma

1.3. Evil

• Undifferentiated liposarcoma
• Mixoid liposarcoma
• Pleomorphic liposarcoma
• Liposarcoma, no other specification

Fibroblastic/Myofibroblastic Tumors

2.1. Blessings

• Nodular Fascitis
• Proliferative Fascitis
• Proliferative Miositis
• Osifying ositis
• Pseudotumor fibr-óseo digital
• Ischemic Fascitis
• Elastofibroma
• Childhood Fibrous Hamaroma
• Fibromatosis colli
• Youth spinal fluid
• Fibromatosis of inclusion bodies
• Fibroma of tendinous pods
• Demoplastic fibroblastoma
• Fibroblastoma type-mamario
• Calcifying aponeurtic fever
• Angiomiofibroblastoma
• Cellular amgiofibroma
• Nucal type
• Gardner Fibroma
• Calcifying fibrous tumor

2.2. Intermediate (locally aggressive)

• Fibromatosis plantar/palmar
• Fibromatosis type desmoid
• Lipofibromatosis
• Giant cell fibroblastoma

2.3. Intermediate (rarely metastatizing)

• Dermatofibrosarcoma protuberans
  • Dermatofibrosarcoma protuberans fibrosarcomatoso
  • Dermatofibrosarcoma protuberans pigmented

• Solitary fibrous tumor
  • Malignant fibrous tumor

• Inflammatory myofibroblastic tumor
• Low-grade myofibroblastic sarcoma
• Mixoinflammary fibroblastic sarcoma/plastic atypical fibroblastic tumor

2.4. Evil

• Adult Fibrosarcoma
• Mixofibrosarcoma
• Low-grade fibromyxoid sarcoma
• Sclerosing epithelioid fibrosarcoma

Fibrohistiocytic tumors

3.1. Blessings

• Tumor of giant cells of tendinosa pod
• Deep benign fibrous histiocytoma

3.2. Intermediate (rarely metastatizing)

• Fibrohistiocytary tumor plexiforme
• Tumor of giant cells of soft parts

Smooth muscle tumors

4.1. Blessings

• Leiomioma of soft tissues

4.2. Evil

• Leiomiosarcoma

Pericytic (Perivascular) Tumors

• Genomic tumor (and variants)
  • Glomangiomatosis
  • Evil glorified tumor

• Miopericitoma
  • Miofibroma
  • Miofibromatosis

• Angioleiomioma

Skeletal Muscle Tumors

6.1. Blessings

• Rabdomioma

6.2. Evil

• Embryonic Rabdomiosarcoma
• Rabdomiosarcoma alveolar
• Pleomorphic Rabdomiosarcoma
• Fusocellular / sclerosing radomyorcoma

Vascular tumors

7.1. Blessings

• Hemangioma
• Hemangioma epithelioid
• Angiomatosis
• Linfangioma

7.2. Intermediate (locally aggressive)

• Hemangioendotelioma kaposiforme

7.3. Intermediate (rarely metastatizing)

• Intralingual papillary angioendothelioma
• Hemangioendothelioma retiforme
• Hemangioendothelioma composite
• Pseudomiogenic hemagioendothelioma (type epithelioid sarcoma)
• Sarcoma de Kaposi

7.4. Evil

• Hemangioendothelioma epithelioid
• Angiosarcoma of soft tissues

Gastrointestinal Stromal Tumors (GISTs)

• Benign GIST
• GIST of uncertain evil potential
• Evil GIST

Nerve Sheath Tumors

9.1. Blessings

• Schwannoma
• Melantic Schwannoma
• Neurofibroma
  • Neurofibroma plexiforme

• Perineuroma
  • Evil Perineuroma

• Granular cell tumor
• Mixed dermal nerve pods
• Solitary circumscribed neuroma
• Ectopian meningioma
• Glue nasal heterotopia
• Benign Triton Tumor
• Hybrid Nervous Vain Tumor

9.2. Evil

• Malignant peripheral nerve pod tumor
• Malignant epithelioid nerve pod tumor
• Tumor Evil Triton
• Malignant granular cell tumor
• Ectomesenquimoma

Tumors of uncertain differentiation

10.1. Blessings

• Fibromixoma acral
• Intramuscular mixture
• Mixoma yuxta-articular
• Deep angiomixoma (aggressive)
• Pleomorphic hyalinizing angiectal tumor
• Timoma hamartomatosus ectopics

10.2. Intermediate (locally aggressive)

• Weiderotic fibrolipomatous tumor

10.3. Intermediate (rarely metastatizing)

• Atypical fibroxantoma
• Histiocytoma fibrous angiomatoid
• Osifying fibromyxoid tumor
• Malignant osifying fibromyxoid tumor
• Mixed tumor
• Evil mixed tumor
• Mioepitelioma
• Myoepithelial carcinoma
• Benign phosphaturgical mesenchymal tumor
• Mesenchymal evil phosphaturgical tumor

10.4. Evil

• Synovial sarcoma
• Epithelioid sarcoma
• Alveolar sarcoma of soft parts
• Clear cell sarcoma
• Extraskeletal Mixoid Condrosarcoma
• Extraskeletal Ewing Sarcoma
• Demoplastic small round cell tumor
• Neoplasias with vascular epithelioid cellular differentiation (PEC)
  • benign PEComa
  • Evil pea
  • Intimal sarcoma

Undifferentiated / unclassifiable sarcomas

• Indifferentiated fusocellular sarcoma
• Indifferentiated pleomorphic sarcoma
• Indifferentiated sarcoma of round cells
• Indifferentiated epithelioid sarcoma
• Indifferentiated sarcoma, without other specification