Chest wall sarcoma is cancer of the bone, cartilage, or soft tissue that protects and supports the organs in the chest cavity. It is one of the rarest forms of cancer. They can be either benign or malignant. Primary tumors can originate from bone or muscle of the chest wall and secondary tumors originate elsewhere in the body and spread (metastasize) to the chest wall. There have been reports suggesting that the survival rate of patients with primary chest wall sarcomas is about 6 years and recurrence is seen in 50% of the cases.
Chest wall sarcoma may be caused by an oncogenic mutation such as translocation, deletion, or gain of function.
Types of chest wall sarcomas include:
Malignant fibrous histiocytoma
Symptoms of chest wall sarcomas vary with the tumor’s classification and severity.
Symptoms of benign (mild) chest wall tumors:
A localized mass
Muscle atrophy (breakdown)
Symptoms of malignant (spread rapidly) chest wall tumors:
A localized mass
Impaired movement or chest expansion
Chest wall sarcoma is comprised of a heterogeneous group of lesions that are challenging to both diagnose and treat. The protocol of diagnosis for a suspected chest wall tumor includes a careful medical history, proper physical examination, and a chest X-ray.
The foregoing may be followed by high-end techniques such as computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET). After a thorough clinical history, and physical examination, if warranted, the patient undergoes a chest radiograph (chest X-ray) that helps to evaluate the size and extension of the tumor. The chest X-ray also provides a prompt evaluation of the lungs for any direct invasion and may detect cortical bone destruction, confirm if the tumor is of bony origin, as well as differentiate malignant from benign chest wall tumors. However, computed tomography is more sensitive than chest radiograph for verifying all of the foregoing. For the evaluation of soft tissues, magnetic resonance imaging (MRI) is superior to computed tomography. MRI helps to differentiate neoplasms from normal chest wall structures and other disease processes developed due to infection or inflammation, and can also fully elucidate the various internal components of complex lesions. PET scan is utilized to identify the stage of the disease, evaluate response to treatment, or detect recurrent disease.
Though all these radiological evaluations can help to ascertain the density and shape of a tumor, they are not conclusive for a definitive diagnosis; a biopsy is essential to confirm the diagnosis. Excisional biopsy is performed for lesions measuring less than five centimeters, and needle aspiration or incisional biopsy is done for lesions greater than five centimeters. Several subtypes of chest wall sarcomas display a characteristic clinical appearance with distinct morphological and immunohistochemical profiles (techniques for identifying disease-specific protein in cells of tissue sections) that aid in the diagnosis.
Additionally, molecular testing with reasonably high sensitivity by fluorescence in situ hybridization (FISH) and polymerase chain reaction (PCR) molecular tools can help confirm a suspected diagnosis and is also useful for high-grade lesions where the morphology or immunohistochemistry (IHC) profile may be non-specific.
Surgical resection is the standard of care for benign tumors. The handling of malignant tumors involves a more interprofessional approach to optimize functional outcomes. The treatment plan takes into account, the type of chest wall tumor of the patient, as well as the size and location of the tumor. Malignant chest wall tumors usually require a combination of chemotherapy, radiation therapy, and/or surgery. Wide tumor excision with negative margins is preferred as they impede local recurrence. If surgery is required, reconstruction of the chest wall and the soft tissue (ribs, muscle, and skin) becomes imperative to ensure that the chest looks and functions normally.
Various types of muscle flaps are employed depending on the location and area of resection to cover most of the chest wall defects, such as pectoralis flap, latissimus dorsi flap, and rectus abdominis flap. Other appliances used for reconstruction include prosthetic mesh and titanium implants in combination with strong synthetic or biologic mesh. Full-thickness chest wall resection has been reported to improve survival, prolong palliation, and cure. However, such surgical procedures are at times accompanied by perioperative morbidity and mortality due to incomplete resection, unsuccessful reconstruction, or in some cases, incorrect diagnosis. Surgical resection along with reconstruction has been identified as the best option for primary tumors, and these procedures may even be curative. Combining surgery with radiation therapy and/or chemotherapy may be indicated in certain cases but it depends on the histopathology of the tumor.
On the basis of recent understanding and findings of specific cancer biology, various emergent therapeutic approaches for chest wall sarcomas are enlisted as follows:
Agents are being developed for targeting immune checkpoints other than PD-1 or a T cell receptor that attaches to a ligand, which is helpful in tumor progression.
Modulating agents are designed for the transition from tumor-promoting to the tumor-suppressive status of macrophages which are mainly responsible for the lysis of abnormal cells.
Cellular therapies, such as a chimeric antigen or CAR-T cell therapies specifically strengthen the adaptive immune response towards the clearance of cancer cells.