a) History and Physical Examination
Presentation will depend largely on the type of sarcoma and location of the tumour. The most common presenting complaint is that of a gradually enlarging, painless mass. The anatomic site of the primary disease represents an important factor influencing treatment and outcome. These tumours may occur anywhere, but the majority are in the extremities. They can become quite large especially in the thigh or retroperitoneum. There may be pain or symptoms associated with compression by the mass, such as paresthesias or edema.
b) Imaging
Magnetic Resonance Imaging (MRI):
- The modality of choice for detecting, characterizing and staging soft tissue tumours due to its ability to distinguish tumour tissue from adjacent muscle and fat, as well as to define relationships to key neurovascular structures.
- The preferred imaging modality for evaluation of soft tissue masses of the extremities, trunk and head and neck.
- Provides better tissue discrimination between normal and abnormal tissues
- Aids in guiding biopsy, planning surgery, evaluating response to treatment, and in the long term follow-up for local recurrence.
Computerized Tomography (CT):
- The preferred imaging modality for primary chest, retroperitoneal and visceral sarcomas.
- A baseline chest CT at the time of diagnosis is recommended for accurate staging, particularly for high-risk sarcomas (>5cm in diameter, deep and high grade).
PET-CT:
- PET scanning is not routinely recommended for initial sarcoma staging workup, but is often used to stage tumours such as Ewing sarcoma and rhabdomyosarcoma.
- There may be a role in selected cases for detecting extrapulmonary metastases.
Bone scan:
- Is usually not helpful for initial staging of soft tissue sarcomas.
Plain radiographs:
- Plain films of the primary site can be useful to rule out soft tissue masses that arise from bone and to detect intratumoral calcifications such as those that appear within soft tissue (extraskeletal) osteosarcoma and synovial sarcomas.
c) Biopsy: principles of biopsy
- A biopsy is necessary to establish malignancy, to assess histologic grade and to determine the specific histologic type of sarcoma. This information is essential to ensure the best outcome for the patient.
- A biopsy should be undertaken only after the tumour has been completely imaged and at the request of the treating surgeon.
- The biopsy should be performed after MRI has been done, as post procedural edema may make the MRI difficult to interpret.
- In collaboration with the treating surgeon, the needle tract (which needs to be excised with the tumour) can be established in keeping with oncologic principles.
- A poorly placed initial biopsy may compromise definitive surgery by affecting subsequent surgical resection, preparation of flaps, and/or cosmetic repair, or result in the need for more extensive surgery to encompass the biopsy site at the time of definitive resection.
- Adequate tissue is required as this affect diagnostic accuracy.
- Contemporary diagnostic approaches to most malignancies, including sarcoma, combine initial morphologic evaluation with diagnostically relevant cytogenetic, molecular and immunohistochemical testing methods. Therefore, the initial biopsy sample should ideally obtain sufficient tissue for these ancillary diagnostic techniques.
Core biopsy
- The preferred method of obtaining tissue is with a well-placed core needle biopsy if technically feasible, with resection of the entire needle tract at the time of definitive surgery.
- CT or ultrasound-guided biopsy of deep lesions can improve the diagnostic accuracy in lesions with cystic areas and necrosis by allowing the operator to select the site to be biopsied.
- In general, a core biopsy has low incidence of complications and high diagnostic accuracy.
Incisional biopsy
- If needed, incisional biopsy should be performed by the surgeon planning the definitive resection.
- Open biopsy incisions should be placed longitudinally along the extremity so that the scar can be resected along with the tumour at the time of definitive resection.
Excisional biopsy
- Should be avoided, particularly for lesions greater than 2 cm on size, since such an approach will make definitive resection more extensive due to contamination of surrounding tissue planes.
Fine needle biopsy
- Is not recommended in the initial diagnostic evaluation of a suspicious soft tissue mass due to limited sampling leading to low diagnostic accuracy and lack of tissue for ancillary diagnostics (eg. Cytogenetics).
- Can be useful in confirming disease recurrence.
d) Pathology
- Pathology specimens of suspected soft tissue sarcoma should be reviewed by a pathologist who specializes in the evaluation of soft tissue sarcomas.
- Diagnostic accuracy relies on a number of factors including appropriate and adequate sampling, quality of tissue obtained, the experience and expertise of the pathologist and the ability to collaborate closely with the treating surgeon to plan appropriate biopsies.
- Histologically, the diagnosis of soft tissue sarcoma is made on the basis of morphologic pattern.
- Novel insights into the molecular pathogenetic basis for sarcomas have reshaped contemporary diagnosis.
- Ancillary techniques are routinely used as an adjunct to morphologic diagnosis including immunohistochemistry and molecular genetic analysis.
- Molecular genetic analyses, such as fluorescence in situ hybridization, reverse transcription polymerase chain reaction, expression profiling and targeted sequencing have increasingly been incorporated into the routine diagnostic workup of these neoplasms.
- Some alterations with known protein correlates have resulted in the establishment of immunohistochemical markers with diagnostic, prognostic and/or predictive properties.
References
- Sinha S, Peach AH. Diagnosis and management of soft tissue sarcoma. BMJ 2010; 341:c7170
- Schaefer IM, Cote GM, Hormick JL. Contemporary diagnosis, genetics and genomics. JCO 2018;36(2):101-111
