Stages of Soft Tissue Sarcoma

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TNM Staging of Soft Tissue Sarcoma

TNM is the most commonly used system for staging STSs of the trunk, extremities (limbs), and retroperitoneum by the medical community. “T” stands for “Tumor Size”, “N” for “Lymph Nodes”, and “M” for “Metastasis”. Numbers and/or letters after T (1, 2, 3, and 4), N (0 and 1), and M (0 and 1) provide more details about each of these factors.

Additionally, STS of the trunk, extremities (limbs), and retroperitoneum is graded to assess the aggressiveness of the disease. A three-tiered French Federation of Cancer Centers Sarcoma Group (FNCLCC) grade system is the most commonly used system to grade the STS.

In this system, the grade of a tumor is determined with the help of 3 parameters: differentiation (appearance of cell morphology under the microscope), mitotic activity (rate of cancerous cell division), and extent of necrosis (extent of dead tissue present in the tumor mass).

Each parameter is scored as follows: differentiation (1–3), mitotic activity (1–3), and necrosis (0–2), where a higher score indicates abnormal cells morphology, high rate of cell division, and presence of high amount of dead tissue, respectively. The scores are added to assign the grade to a tumor, where G1 = a score of 2 or 3; G2 = a score of 4 or 5; and G3 = a score of 6 to 8.

Once T, N, and M categories and the overall grade of a tumor are determined through different diagnostic techniques, this information is combined to assign an overall stage (from 0 to IV) to the disease. Following table describes the characteristics of different stages assigned to the STS of the trunk, extremities (limbs), and retroperitoneum:

STAGE TNM and GRADE Trunk & Extremities Retroperitoneum
IA T1 N0 M0 G1/X The primary tumor is </=5 cm in size. No spread to nearby lymph nodes or distant body parts. The assigned grade is G1 or grade could not be assigned or is unknown. The primary tumor is </=5 cm in size. No spread to nearby lymph nodes or distant body parts. The assigned grade is G1 or grade could not be assigned or is unknown.
IB T2-4 N0 M0 G1/X The primary tumor size may range from >5 cm to >15 cm. No spread to nearby lymph nodes or distant body parts. The assigned grade is G1 or grade could not be assigned or is unknown. The primary tumor size may range from >5 cm to >15 cm. No spread to nearby lymph nodes or distant body parts. The assigned grade is G1 or grade could not be assigned or is unknown.
II T1 N0 M0 G2-3 The primary tumor is </=5 cm in size. No spread to nearby lymph nodes or distant body parts. The assigned grade is G2 or G3. The primary tumor is </=5 cm in size. No spread to nearby lymph nodes or distant body parts. The assigned grade is G2 or G3.
IIIA T2 N0 M0 G2-3 The primary tumor is >5 cm but </=10 cm in size. No spread to nearby lymph nodes or distant body parts. The assigned grade is G2 or G3. The primary tumor is >5 cm but </=10 cm in size. No spread to nearby lymph nodes or distant body parts. The assigned grade is G2 or G3.
IIIB T3-4 N0 M0 G2-3 The primary tumor size may range from >10 cm to >15 cm. No spread to nearby lymph nodes or distant body parts. The assigned grade is G2 or G3. The primary tumor size may range from >10 cm to >15 cm. No spread to nearby lymph nodes or distant body parts. The assigned grade is G2 or G3.
  Any T N1 M0 Any G N/A The primary tumor of any size. The disease has spread to nearby lymph nodes. No spread to distant body parts. The assigned grade may have any value.
IV Any T N1 M0 Any G The primary tumor of any size. The disease has spread to nearby lymph nodes. No spread to distant body parts. The assigned grade may have any value. N/A
  Any T Any N M1 Any G The primary tumor of any size that might or might not have spread to nearby lymph nodes. The disease has spread to distant body parts, such as the lungs. The assigned grade may have any value. The primary tumor of any size that might or might not have spread to nearby lymph nodes. The disease has spread to distant body parts, such as the liver or lungs. The assigned grade may have any value.

Stage grouping for STS in the abdomen, thoracic visceral organs, and Head & neck region require further data collection and has not been established yet.

Sarcoma Staging Investigations

Imaging Tests

Ultrasound

ultasound for sarcoma This test can distinguish between fluid-filled cysts (usually benign) and solid tumor masses. The ultrasound test does not use any ionizing radiation and is considered as safe.

Computed tomography (CT) scan

CT Scan This technique can accurately detect the tumor’s size, location, invasion to nearby structures (for example, the bones), and spread to distant body parts (for example, the lungs and the liver). Sometimes, it can distinguish between a benign and a cancerous change and can even reveal the type of tissue involved (and thus the type of STS). This is very helpful for planning the treatment in case radiation therapy is indicated for the treatment. It can also be used to guide a biopsy needle to collect biopsy samples from the affected area.

Magnetic resonance imaging (MRI) scan

MRI Scan This technique provides detailed images of soft tissues in the body using radio waves, strong magnetic field, and gadolinium – the contrast material, which is used via intravenous injection to improve the clarity of the MRI images.

Similar to CT, it can accurately diagnose the size, location, extent of invasion, and spread of disease to distant body parts, especially soft tissues like the muscles, eyeballs, blood vessels, brain, and spinal cord.

Sometimes, it can distinguish between a benign and a cancerous change and can even reveal the type of tissue involved (and thus the type of STS).

It is better than CT for the examination of soft tissues in the limbs, but inferior to CT for examining the bones. Additionally, similar to CT, it can be used in planning radiation treatment for STSs. It can also be used to guide a biopsy needle to collect biopsy samples from the affected area.

Positron emission tomography (PET) scan

PET Scan The areas of higher radioactivity indicate cancerous tissue on the PET scan. This technique can be combined with CT scan (PET/CT) to accurately diagnose the extent of disease in distant body parts.

Biopsy

biopsy sample It can establish the diagnosis of STS, the type of STS, the severity of cancerous changes involved (grade of cancer), and the presence of specific defective genes. The detected defect(s) can be targeted with the help of an appropriate treatment approach.

Following are common techniques used for collecting the biopsy samples from the affected area/lymph nodes:

Core Needle Biopsy

In this technique, a hollow needle attached to a syringe is used to collect the biopsy sample from the affected area/lymph node. A small sample of tissue is usually obtained with this technique that can be tested to establish the diagnosis of the STS. A fine needle aspiration can be utilized to diagnose disease progression or recurrence in patients who have received treatment.

Surgical biopsy

In this technique, a tissue sample from the affected site is removed surgically. When only a part of the affected tissue is removed, the procedure is known as the incisional biopsy. While in the case of excisional biopsy, the whole tumor is removed surgically. The magnitude of the procedure depends upon the location and the size of the tumor. Excisional biopsy is usually performed when the tumor is located at an accessible site and do not involve any critical structure. It usually combines both diagnosis and treatment for the STS.

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