Clinical Profile:

A 50-year-old grocery shopkeeper presented with a swelling on the right anterior chest wall since one year. The swelling was round, firm, non-fluctuant and immobile.

Radiological diagnosis:

Chest wall tumors can arise primarily from vessels, nerves, soft tissue or bone; or can be secondary in origin (example: metastasis).

They can be benign or malignant

In this case, there is no fat component; thus ruling out lipoma or liposarcoma.

There is no bone erosion; bony origin is ruled out.

Characteristic vascular enhancement is not seen, hence vascular origin is ruled out.

Nerve sheath tumors typically show rib erosions or calcifications, hence this diagnosis is less likely.

So, it can be tumor which is secondary in origin.

There is no evidence of mediastinal, hilar or cervical enlarged lymph nodes making the diagnosis of lymphoma less likely.

With no history of radiation exposure, radiation associated malignancies are unlikely.

Radiological diagnosis:

Chest wall invasion by intrathoracic tumour (lung cancer, pleural tumours)

Soft tissue metastasis (not bony).

Pathological diagnosis:

Ultrasound guided biopsy of the mass was done which showed a high grade malignant tumor with spindle and epitheloid cells.
On immunohistochemistry, the cells express AE1/AE3, calretinin and WT1. The above histopathology findings were suggestive of malignant biphasic mesothelioma.

Discussion

Pleural malignant mesothelioma arises from mesothelial cells of the pleura. Approximately 80% of cases of malignant mesothelioma are of pleural origin.

Etiopathogenesis: Exposure to asbestos is an important risk factor for the development of malignant pleural mesothelioma (MPM) [1]. Asbestos fibers accumulating in the alveoli can reach the pleura through lymphatics or direct penetration. Furthermore, they may cause fibrosis, pleural plaque and malignant pleural mesothelioma [2,3].

Idiopathic or spontaneous mesothelioma are those mesothelioma, that occur in the absence of any exposure to asbestos or erionite, and they are strongly associated with germline alterations in BRCA-associated protein-1 gene (BAP1) [4].

Clinical presentation: Mesotheliomas usually present as dyspnea, chest pain, weight loss and chest wall mass. Breathlessness is due to a pleural effusion .

Histopathological features - Three histological cell types ― epithelioid, sarcomatoid and biphasic.

Epithelioid mesothelioma is the most common. It is also the most treatable form of the disease.

Sarcomatoid mesothelioma is the deadliest type. The spindle-shaped sarcomatoid cells are spaced farther apart than epithelial cells, making these cancer cells more likely to spread throughout the body.

In biphasic mesothelioma, both epithelioid and sarcomatoid cells are present in the tumors. Diagnosing biphasic mesothelioma can be a challenge. While a biopsy is the only way to determine the histological cell type of the cancer, a biopsy only samples a particular tissue or tissues . The prognosis for biphasic mesothelioma depends upon the proportion of epithelioid cells to sarcomatoid cells [5].

Radiological features:

Computed tomography : CT is the primary imaging modality used for the evaluation of malignant mesothelioma (MPM). The key CT findings include unilateral pleural effusion, nodular pleural thickening, interlobar septal thickening, pleura-based mass lesion, calcified pleural plaques and contraction of ipsilateral hemithorax with ipsilateral mediastinal shift & elevation of hemidiaphragm.

MPM is locally aggressive, with frequent invasion of the chest wall, mediastinum, and diaphragm. Chest wall involvement may manifest as obliteration of extra-pleural fat planes, invasion of intercostal muscles, displacement of ribs or bone destruction [6].

Pulmonary metastases of MPM manifesting as peri lymphatic nodules and masses, metastasis to mediastinal and retro-crural nodes can be evaluated, but its accuracy remains suboptimal because enlarged nodes do not prove nodal involvement [7].

MR imaging: It helps to differentiate normal from tumor tissue. Relative to chest wall muscle, the MPM is Iso or slightly hyperintense on T1, moderately hyperintense on T2 and enhances with use of gadolinium contrast. It is superior to CT in the evaluation of local invasion and resectabilty of the tumor because of excellent contrast resolution of MR imaging which allow improved detection of tumor extension, especially to the chest wall and diaphragm [6].

PET : Because it can provide both anatomic and metabolic information about a lesion, PET is useful in the staging and preoperative evaluation of MPM. PET has increased accuracy in the detection of mediastinal nodal metastases [8].

Staging:

TNM (tumor-node-metastasis) staging system from international mesothelioma interest group, aids in determining treatment options.

The above-described case belongs to T3 stage (locally advanced, potentially resectable).

Prognosis - is poor, with a median survival time of 12 months after diagnosis (10). Several factors have been shown to correlate with reduced survival time: intrathoracic lymph node metastases, distant metastatic disease, and extensive pleural involvement [9]. Treatment – Patient with early stages benefits from mesothelioma surgery ( extra-plural pneumonectomy and pleurectomy and decortication ). Best chance for living longer life. Chemotherapy help to remove the all the viable tissue from the chest area. Radiation therapy control the symptoms when surgery is not an option.

References:

1. Lanphear BP, Buncher CR. Latent period for malignant meso- thelioma of occupational origin. J Occup Med 1992;34:718– 21.

2. Carbone M, Kratzke RA, Testa JR. The pathogenesis of meso- thelioma. Semin Oncol 2002;29:2–17.

3. Boutin C, Dumortier P, Rey F, Viallat JR, de Vuyst P. Black spots concentrate oncogenic asbestos fibers in the parietal pleura. Thoracoscopic and mineralogic study. Am J Respir Crit Care Med 1996;153:444–9.

4. Rusch A, Ziltener G, Nackaerts K, Weder W, Stahel RA, Felley-Bosco E. Prevalence of BRCA-1 associated protein 1 germline mutation in sporadic malignant pleural mesothelioma cases. Lung cancer. 2015 Jan 1;87(1):77-9

5.Alì G, Bruno R, Fontanini G. The pathological and molecular diagnosis of malignant pleural mesothelioma: a literature review. Journal of thoracic disease. 2018 Jan;10(Suppl 2):S276.

6.Patz Jr EF, Shaffer K, Piwnica-Worms DR, Jochelson M, Sarin M, Sugarbaker DJ, Pugatch RD. Malignant pleural mesothelioma: value of CT and MR imaging in predicting resectability. AJR. American journal of roentgenology. 1992 Nov 1;159(5):961-6.

7.Boiselle PM, Patz Jr EF, Vining DJ, Weissleder R, Shepard JA, McLoud TC. Imaging of mediastinal lymph nodes: CT, MR, and FDG PET. Radiographics. 1998 Sep;18(5):1061-9.

8. Benard F, Sterman D, Smith RJ, Kaiser LR, Albelda SM, Alavi A. Metabolic imaging of malignant pleural mesothelioma with fluorodeoxyglucose positron emission tomography. Chest. 1998 Sep 1;114(3):713-22.

9. Rusch VW. A proposed new international TNM staging system for malignant pleural mesothelioma: from the International Mesothelioma Interest Group. Chest 1995; 108:1122-1128.

10. Aisner J. Current approach to malignant mesothelioma of the pleura. Chest. 1995 Jun 1;107(6):332S-44S.

Acknowledgement:

We are grateful to the Department of Pathology at our institution for providing the images of the histological appearance and their description.