Indian Journal of Pathology and Microbiology

: 2021  |  Volume : 64  |  Issue : 4  |  Page : 834--836

Thigh mass in a patient with malignant pleural mesothelioma: Metastasis at an unusual site

S Sunitha, Ashini H Shah, Amisha Gami, Priti Trivedi 
 Department of Oncopathology, Gujarat Cancer Research Institute, Ahmedabad, Gujarat, India

Correspondence Address:
Ashini H Shah
Department of Oncopathology, Gujarat Cancer Research Institute, Ahmedabad, Gujarat, India. E.mail:


Soft tissue tumors are a highly heterogeneous group of lesions with varied clinical presentation. The majority is primary tumors and metastatic tumors are very rare. Malignant pleural mesothelioma presenting as a soft tissue mass at a distant site is even rarer and can cause diagnostic challenges both clinically and pathologically. We report a case of malignant pleural mesothelioma presenting as a soft tissue mass in the left thigh. A 59-year-old man, non-smoker, working in a cement factory since 30 years presented with complains of difficulty in walking since 1½ months. Review of his previous medical records revealed malignant pleural mesothelioma, which was diagnosed 9 months before. He had denied chemotherapy and was on Ayurvedic medication. The lesion involved the adjacent intercostal muscles. Few enlarged lymph nodes were noted in mediastinal and cervical regions. Biopsy of left supraclavicular and right cervical lymph nodes showed metastases. Metastasis from malignant pleural mesothelioma to the thigh was confirmed by immunohistochemistry. The tumor was positive for CK5/6, CK7, Calretinin and vimentin and immunonegative for CEA, Napsin A and TTF 1.

How to cite this article:
Sunitha S, Shah AH, Gami A, Trivedi P. Thigh mass in a patient with malignant pleural mesothelioma: Metastasis at an unusual site.Indian J Pathol Microbiol 2021;64:834-836

How to cite this URL:
Sunitha S, Shah AH, Gami A, Trivedi P. Thigh mass in a patient with malignant pleural mesothelioma: Metastasis at an unusual site. Indian J Pathol Microbiol [serial online] 2021 [cited 2023 Jan 30 ];64:834-836
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Full Text


Malignant mesothelioma is a rare neoplasm with aggressive behavior. It arises from mesothelial surfaces of pleural cavity, peritoneal cavity, pericardium or tunica vaginalis. Patients with malignant pleural mesothelioma (MPM) initially present with pulmonary symptoms and distant skeletal muscle metastasis is very rare.[1],[2] We report a case of MPM in an asymptomatic, 59-year-old non-smoker male, who presented with muscular metastasis in thigh.

 Case Report

A 59-year-old gentleman presented with difficulty in walking and tightness in the left thigh for 1 ½ months. There was no cough or breathlessness or chest pain. He gave a history of weight loss. He was a non-alcoholic and non-smoker. His general condition was good. All his biochemical, hematological parameters were normal. X-ray of the hip joint was normal. Magnetic resonance imaging showed a 22 × 13 × 11 cm3-sized heterogeneously enhancing soft tissue mass involving medial compartment of left thigh. The possibility of soft tissue sarcoma was suggested. Subsequently, patient developed cervical lymphadenopathy in left supraclavicular region. The biopsy of thigh mass showed moderately pleomorphic epithelioid cells having large hyperchromatic nucleus and abundant vacuolated cytoplasm arranged in pseudoglandular pattern [Figure 1]. Report was given as possibility of metastatic carcinoma and immunohistochemistry (IHC) was advised.{Figure 1}

Previous medical records of the patient were reviewed. Nine months before, the patient had undergone pleural biopsy in a well-known private hospital to rule out tuberculosis, as haziness was noted in lung fields during routine chest X-ray. This was noticed during regular health check-up done in the cement factory where he was working for 30 years. A biopsy report was given as malignant pleural mesothelioma. He had denied chemotherapy and was on Ayurvedic medication. IHC showed that tumor was positive for CK 7 and CK5/6, focally positive for vimentin and immunonegative for TTF1 and Napsin A.

Chest X-ray showed bilateral apical pleural thickening, hilar prominence, an ill-defined soft tissue opacity in right lower zone tracking along right lateral aspect of mid zone and blunting of right CP angle. Computed tomography showed a heterogeneously enhancing nodular soft tissue thickening involving costal, mediastinal and diaphragmatic pleura in right hemithorax, erosion of ninth and tenth ribs and extrathoracic extension [Figure 1]a. Some enlarged lymph nodes were noted in the cervical, perivascular, pericarinal and paravertebral regions. Biopsy of left cervical lymph nodes and thigh mass showed a similar morphology confirming metastases from common primary tumor. Immunohistochemical analysis performed on both tissues showed similar results. They were positive for CK5/6 [Figure 1]c, CK7 [Figure 1]d, Calretinin [Figure 1]e and vimentin and immunonegative for CEA, Napsin A [Figure 1]f and TTF 1 [[Figure 1f, Inset]. Metastases from malignant mesothelioma were confirmed. The patient continued Ayurvedic treatment and was lost to follow-up.


Malignant mesothelioma is a highly fatal neoplasm known for rapid progression and metastases. We report a case of MPM complicated by skeletal muscle metastasis. His initial clinical presentation was muscular symptoms rather than pulmonary symptoms, whereas MPM was incidentally diagnosed 9 months before. Subsequently, he developed multiple lymph node metastases. This highly aggressive tumor, when presented with unusual manifestations, can cause diagnostic confusion as in our case.

Malignant pleural mesothelioma arises from mesothelial surfaces of pleural cavity. It is related to asbestos exposure as in our case.[3],[4] Although cement products may contain only 10% of asbestos, it is enough to make the mix dangerous. Asbestos is added to make the cement stronger. In 2015, a Polish study analyzed the rates of asbestos-related cancer among asbestos product factories. The highest rate of mesothelioma occurred among asbestos-cement workers, at 6.54 cases/1000 workers. However, cases not related to asbestos have also been reported.[1]

The three histology subtypes of malignant mesothelioma are epithelioid, sarcomatoid and biphasic (mixed) variants. Many immunohistochemical markers are now available to support the diagnosis of malignant mesothelioma.[1],[5] The commonly used biomarkers are calretinin, CK5/6, Wilm's tumor-I (WT-I) and D2-40 (podoplanin) antigens.[6],[7] MPM is locally aggressive and invasion of chest wall, mediastinum and diaphragm is common.[8] Our case also showed the chest wall invasion with involvement of ribs and intercostal muscle. Metastasis to hilar and mediastinal lymph nodes is seen in 40%-45% of patients, whereas extrathoracic lymph node metastasis is rare.[9] Our case showed metastasis in bilateral cervical lymph nodes. Metastasis to unusual sites like bone, lung, liver, central nervous system and soft tissue is rarer.[6]

Very few cases of MPM with skeletal muscle metastasis are documented in the literature. This is the sixth case according to our knowledge. The first case was reported by Grellner W et al. in 1995, based on autopsy findings. Metastases were noted in left temporal muscle, proximal limb muscles of the right upper arm and both thighs.[10] In 1999, Laurini, et al. reported a case of MPM with a solitary forearm mass.[2] Aukema, et al. in 2009 reported extensive soft tissue metastases, detected by whole body FDG-PET/CT scan.[11] In 2014, Chia-Chun Chiang, et al. reported a case with disseminated skeletal muscle metastases. The patient died 3 months after the onset of symptoms.[1] In 2017, Irene Moysset et al. reported a case with metastasis in the abdomen and left buttock.[5]

Local heat production due to muscular action, possible effects of lactic acid metabolism creating a poor milieu for tumor cells, cellular and humoral immune factors in local environment of skeletal muscle are negative factors of metastatic growth.[12] The “seed and soil” hypothesis postulated by Paget states that the formation of metastases depends on the interaction of specially adapted tumor cells (seeds) and a permissive organ environment (soil). Tumor cells accumulate specific genetic mutations and acquire the ability to intravasate into the vasculature. They disseminate hematogenously into target organs. The cells suited to grow in diverse cellular microenvironment will develop into metastases.[13] The use of more sensitive imaging modalities like multislice CT, MRI and FDG-PET/CT can detect more of such cases.[1],[8],[11]


MPM is a highly malignant tumor having aggressive behavior. It can cause widespread lympho-hematogenous metastases and present as mass at unusual locations and organs, including distant skeletal muscle. When present as initial mode of presentation, causes diagnostic confusion. But awareness and timely use of correct immunohistochemical markers helps the pathologist to make a correct diagnosis.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

  1. Department of Immunohematology and IHC, Gujarat Cancer Research Institute, Ahmedabad, Gujarat, India.
  2. Department of Radiodiagnosis, Gujarat Cancer Research Institute, Ahmedabad, Gujarat, India.

Conflicts of interest

There are no conflicts of interest.


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