Diagnosis
Soft tissue sarcomas are a heterogeneous group of cancers, with more than 100 different forms described by the World Health Organization in 2013. Diagnosis is confirmed with a core-needle or incisional biopsy reviewed by a pathologist with experience in diagnosing sarcomas. It is important that the biopsy is carefully obtained to avoid compromising future resections.
Staging
Staging and grading of soft tissue sarcoma is important for determining the most effective treatment options. Staging includes MRI or CT imaging of the primary tumor location as well as thorough review of biopsy specimens. A chest CT scan is recommended to detect lung metastases for any sarcomas larger than 5 centimeters or with moderate to poor differentiation. Staging for soft tissue sarcoma depends on the location of the tumor.
Table 1: Definitions for TNM Staging of Soft Tissue Sarcomas (STS)
| Categories | STS of Trunk, Extremities, and Retroperitoneum | STS of the Head and Neck | STS of the Abdomen and Thoracic Visceral Organs |
| TX | Primary tumor cannot be assessed | Primary tumor cannot be assessed | Primary tumor cannot be assessed |
| T0 | No evidence of primary tumor | ||
| T1 | Tumor <5 cm | Tumor <2 cm | Organ confined |
| T2 | Tumor >5 cm and <10 cm | Tumor >2 to >4 cm | Tumor extension into tissue beyond organ |
| T2a | Invades serosa or visceral peritoneum | ||
| T2b | Extension beyond serosa (mesentery) | ||
| T3 | Tumor >10 cm and <15 cm | Tumor >4 cm | Invades other organs |
| T4 | Tumor >15 cm | Tumor with invasion of adjoining structures | Multifocal involvement |
| T4a | Tumor with orbital invasion, skull base/dural invasion, invasion of central compartment viscera, involvement of facial skeleton, or invasion of pterygoid muscles | Mulitfocal (2 sites) | |
| T4b | Tumor with brain parenchymal invasion, carotid artery encasement, prevertebral muscle invasion, or central nervous system involvement via perineural spread | Multifocal (3-5 sites) | |
| T4c | Multifocal (>5 sites) | ||
| N0 | No regional lymph node metastasis or unknown lymph node status | No regional lymph node metastasis or unknown lymph node status | No regional lymph node involvement or unknown lymph node status |
| N1 | Regional lymph node metastasis | Regional lymph node metastasis | Lymph node involvement present |
| M0 | No distant metastasis | No distant metastasis | No metastasis |
| M1 | Distant metastasis | Distant metastasis | Metastasis present |
Grade should be recorded for all soft tissue sarcomas and is based on tumor differentiation, mitotic count, tumor necrosis, and histology. The French Federation of Cancer Centers Sarcoma Group (FNCLCC) gives a score for each parameter, which is then added together to determine the histologic grade of the tumor. The scoring is as follows:
Tumor Differentiation
1 Sarcomas closely resembling normal adult mesenchymal tissue (eg, low-grade leiomyosarcoma)
2 Sarcomas for which histologic typing is certain (eg, myxoid/round cell liposarcoma)
3 Embryonal and undifferentiated sarcomas, sarcomas of doubtful type, synovial sarcomas, soft tissue osteosarcoma, Ewing sarcoma/primitive neuroectodermal tumor (PNET) of soft tissue
Mitotic Count
1 0-9 mitoses per 10 high-power fields (HPF) using a 40x objective
2 10-19 mitoses per 10 HPF
3 >20 mitoses per 10 HPF
Tumor Necrosis
0 No necrosis
1 <50% tumor necrosis
2 >50%tumor necrosis
Table 2: Definition of Histologic Grade
| G | G Definition |
| GX | Grade cannot be assessed |
| G1 | Total differentiation, mitotic count, and necrosis score of 2 or 3 |
| G2 | Total differentiation, mitotic count, and necrosis score of 4 or 5 |
| G3 | Total differentiation, mitotic count, and necrosis score of 6, 7, or 8 |
Table 3: American Joint Committee on Cancer (AJCC) Stage Groups for Soft Tissue Sarcoma of the Trunk, Extremities, and Retroperitoneum
| Stage | T | N | M | Grade |
| IA | T1 | N0 | M0 | GX, G1 |
| IB | T2, T3, T4 | N0 | M0 | GX, G1 |
| II | T1 | N0 | M0 | G2, G3 |
| IIIA | T2 | N0 | M0 | G2, G3 |
| IIIB | T3, T4 | N0 | M0 | G2,G3 |
| IIIB/IV | Any T | N1 | M0 | Any G |
| IV | Any T | Any N | M1 | Any G |
REFERENCES
- National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology. Soft Tissue Sarcoma. v2.2019. https://www.nccn.org/professionals/physician_gls/pdf/sarcoma.pdf. Accessed March 14, 2019.
- National Cancer Institute. Adult Soft Tissue Sarcoma Treatment (PDQ) – Health Professional Version. https://www.cancer.gov/types/soft-tissue-sarcoma/hp/adult-soft-tissue-treatment-pdq#section/_193. Accessed March 14, 2019.
- PDQ Adult Treatment Editorial Board. Adult Soft Tissue Sarcoma Treatment (PDQ®): Health Professional Version. PDQ Cancer Information Summaries [Internet]. Bethesda (MD): National Cancer Institute (US); 2002-.2018 Jun 29.
- Pollack RE, Maki RG, Baldini EH, et al. Soft tissue sarcoma of the trunk and extremities. In: Amin MB, Edge SB, Greene FL, et al. AJCC Cancer Staging Manual. 8th New York, NY: Springer, 2017, pp 531-537.
- Yoon SS, Maki RG, Asare EA, et al. Soft tissue sarcoma of the trunk and extremities. In: Amin MB, Edge SB, Greene FL, et al. AJCC Cancer Staging Manual. 8th New York, NY: Springer, 2017, pp 507-515.
