Soft Tissue Sarcoma Knowledge Centre
Diagnosis
Introduction
Some of the information within this section is taken from the ESMO clinical guidelines and its use is subject to permission from ESMO.
The standard approach to diagnosis consists of multiple core needle biopsies. However, an excisional biopsy may be the most practical option for <5 cm superficial lesions. An open biopsy may be another option in selected cases. The biopsy should be performed by a trained surgeon, or discussed between the surgeon and the radiologist. It should be planned in such a way that the bioptic pathway and the scar can be safely removed on definitive surgery, and should be preceded by imaging (contrast-enhanced MRI is the preferred method for limb and superficial trunk lesions).
Histological diagnosis should be made according to the WHO classification. The malignancy grade should be provided in all cases in which this is feasible based on available systems. In Europe, the Fédération Nationale des Centres de Lutte Contre le Cancer (FNLCC) grading system is generally used, which distinguishes three malignancy grades. A core biopsy may underestimate the tumor malignancy grade, so that, when preoperative treatment is an option, radiological imaging may add to pathology in providing the clinician with information which helps to estimate the malignancy grade.
Pathologic diagnosis relies on morphology and immunohistochemistry. It should be complemented by molecular pathology (FISH, RT–PCR), to be performed in a laboratory enrolled in an external quality assurance program, in particular when the clinical pathologic presentation is unusual, or the histologic diagnosis is doubtful. The tumor sample should be fixed in formalin (Bouin fixation should be avoided, since it may impair the feasibility of molecular analysis). Collection of frozen tissue and tumor imprints (touch preps) is encouraged, because new molecular pathology assessments may become available later on and be made in the patient’s interest. Informed consent for tumor banking should be sought that allows for later analysis and research.
Tumor site should be properly recorded. Tumor size and tumor depth (in relation to the muscular fascia) should be recorded, since they entail a prognostic value, along with the tumor malignancy grade.
Morphological assessment
Morphological assessment is performed to evaluate disease extension, notably to identify a possible extension of the tumour to the vascular system or to adjacent bone structures and organs. Morphological imaging may also help determine the tumour type and make treatment decisions and includes computed tomography (CT) scan and magnetic resonance imaging (MRI). MRI is the technique of choice for limb localisations, whereas CT scan examination is preferred for tumours arising in the abdomen or the chest. Clinicopathological staging of the tumour is essential for determining the most effective treatment strategy. The classification systems most frequently used are based on the size (T1:<5 cm, T2:>5 cm) and histologic grade (1-3) of the tumour, and also differentiate between superficial (above the superficial fascia) and deep lesions1.
Prognostic factors
The risks of local recurrence, metastatic relapse or disease-related death depend on several factors, including the type and location of the tumour and patient clinical management1,2. Young age, female sex, low histologic grade and stage 1 tumours are associated with good prognosis and low invasiveness, whereas the prognosis for patients with high-grade (grade 3) stage 2 tumours, positive (R1 or R2) resection margins, local relapses, or aggressive histologic subtypes is generally poor.
Diagnostic workup
Precise histologic examination of a tumour specimen is required to confirm the diagnosis before treatment is initiated. For all soft tissue tumours of unknown aetiology it is essential to have a careful review of the biopsy tissue. After histopathological examination, samples are processed and stored for molecular analysis.
References:
1. Erba E, Bergamaschi D, Bassano L, et al. Ecteinascidin-743 (ET-743), a natural marine compound, with a unique mechanism of action. Eur J Cancer. 2001;37:97-105.
2. Grosso F, Jones RL, Demetri GD, et al. Efficacy of trabectedin (ecteinascidin-743) in advanced pretreated myxoid liposarcomas: a retrospective study. Lancet Oncol. 2007;8(7): 595-602.