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Isolated asymptomatic skeletal muscle metastasis in a potentially resectable non-small cell lung cancer: detection with FDG PET-CT scanning.

Introduction

Lung cancer is one of the leading causes of cancer deaths and despite advances in diagnosis and treatment, the overall 5-year survival remains dismal at 14% for all stages (clinical staging)[1]. Distant metastases in lung cancer commonly involve the adrenal glands, liver, bones and brain[2]. Since the extent of disease decides the treatment options, radiological imaging plays an important role in staging evaluation. Positron emission tomography positron emission tomography: see PET scan.
positron emission tomography (PET)

Imaging technique used in diagnosis and biomedical research.
 (PET) imaging with [[sup.18] F]fluorodeoxyglucose (FDG) is now being increasingly used for characterizing lung nodules, for initial staging, restaging, treatment planning and assessing response to treatment in lung cancer[3]. We report a rare site of metastasis to the skeletal muscle in a case of lung cancer detected at initial staging with FDG PET-CT.

Case Report

A 36-year-old man with a 12-year smoking history presented with cough and weight loss for 2 months. A chest radiograph revealed a well-defined opacity in the left upper lobe.

A contrast enhanced computed tomography (CT) scan was performed which showed a 6.0 x 5.4 cm sized lobulated mass in the left upper lobe that did not involve the chest wall or the mediastinal mediastinal /me·di·as·ti·nal/ (-as-ti´n'l) of or pertaining to the mediastinum.

mediastinal

of or pertaining to the mediastinum.
 structures. An ipsilateral ipsilateral /ip·si·lat·er·al/ (ip?si-lat´er-al) situated on or affecting the same side.

ip·si·lat·er·al
adj.
Located on or affecting the same side of the body.
 mediastinal paraaortic node was noted measuring 1.5 cm in size. CT guided biopsy of the lung mass revealed a histopathological diagnosis of adenocarcinoma. On the basis of these findings, the tumor was staged as T2N2Mx and deemed potentially resectable re·sect·a·ble
adj.
Suitable for resection.
. A whole body [[sup.18] F]FDG PET-CT scan was performed as per the hospital protocol for potentially operable lung cancers. It revealed increased FDG uptake in the primary mass and the mediastinal paraaortic node (standardized uptake value (SUV) 16.5 and 7.9 respectively). Focal increased FDG uptake was also seen in the left gluteus maximus muscle (SUV 8.0) and there were no other areas of increased FDG uptake. The gluteal gluteal /glu·te·al/ (gloo´te-al) pertaining to the buttocks.

glu·te·al
adj.
Of or relating to the buttocks.



gluteal

pertaining to the buttocks.
 nodule was not palpable on clinical examination. Ultrasonography (USG) was performed to evaluate the gluteal lesion followed by guided fine needle aspiration fine needle aspiration Diagnostics A method of in which a thin or “skinny”–18- to 23-gauge needle is used to suck in cells or tissue bits for diagnoses; the sites selected for FNAs are often guided by radiologists with fluoroscopy, CT, MRI  cytology (FNAC). USG showed a 1.2 x 1.0 cm sized hypoechoic nodule in the gluteus maximus muscle. Cytology from the gluteal nodule revealed adenocarcinoma cells consistent with the known primary in the lung.

[FIGURE 1 OMITTED]

In view of skeletal muscle metastasis, the patient was upstaged (stage IV) and the intent of the treatment changed from potentially curative surgery to palliative systemic chemotherapy.

Discussion

Lung cancer is one of the leading causes of cancer death in both men and women worldwide. Most patients present at an advanced stage and hence despite developments in diagnosis and treatment the mortality remains high. Distant metastases of lung cancer commonly involve the adrenal glands, bone and brain. Contrast-enhanced CT scan of the thorax (including the adrenals) along with a radionuclide bone scan Radionuclide bone scan
A test that tells if cancer has spread to the bones.

Mentioned in: Lung Cancer, Small Cell
 and brain imaging (with CT or magnetic resonance imaging magnetic resonance imaging (MRI), noninvasive diagnostic technique that uses nuclear magnetic resonance to produce cross-sectional images of organs and other internal body structures.  (MRI)) was considered as optimal staging work up prior to the advent of PET scanning.

Metastases to skeletal muscle from primary lung cancer primary lung cancer Oncology Lung cancer arising in lung tissue–eg, trachea, bronchial tree, parenchyma. See Bronchoalveolar carcinoma, Small cell carcinoma, Squamous cell carcinoma. Cf Metastatic lung cancer.  is a rare event with very few reports described in the literature[4-6]. Various physiological factors like tissue blood flow, pressure and metabolism have been cited as the possible reasons why metastases to skeletal muscle are rare. According to some studies, the presence of proteases and certain inhibitors in muscle tissue are responsible for blocking tumor invasion and growth[7,8].

It has been shown that FDG PET is an excellent imaging modality for metastatic evaluation with the exclusion of the brain. It can detect occult metastases in about 10-20% of cases of non-small cell lung carcinoma (NSCLC NSCLC non (or cancer).
NSCLC Non-small cell lung cancer, see there
)[9-11]. In a study of 167 patients of NSCLC (stages I-III), FDG PET detected unsuspected distant metastases in a high proportion of patients who were otherwise candidates for potentially curative treatment [12]. However, of the 32 cases of distant metastases in the study, there were no cases of skeletal muscle metastasis, emphasizing the rarity of the event. Most cases of skeletal muscle metastases described in the literature presented with clinical symptoms of pain and swelling at the affected site. However, our patient had no symptoms related to the site of skeletal muscle metastasis. It was only suspected after the PET-CT study, which revealed intense focal uptake in the gluteus maximus muscle. Although focal FDG uptake in the deeper subcutaneous tissue of the gluteal region is not uncommonly observed as a result of injection site inflammation, the intense nature of the uptake and its deep location in the muscle was suspicious enough to warrant further evaluation. A USG guided FNAC confirmed the metastatic nature of the gluteal lesion. Detection of solitary extra-pulmonary FDG uptake in patients with recently diagnosed lung cancer, as is the case in our report, should be critically analyzed as nearly half of these lesions may represent a malignant etiology[13]. The increasing use of PET-CT as a whole body staging tool for various cancers has recently led to several reports describing unsuspected distant metastases at unusual locations. Unusual metastases of lung cancer to colon and to the extraocular muscles that were detected by PET-CT have been reported [14,15].

[FIGURE 2 OMITTED]

There is no consensus on the optimal treatment strategy for skeletal muscle metastases and although the options could include radiotherapy, chemotherapy or excision, the outcome remains poor. Although radical treatment of the primary and the solitary metastatic lesion could have been considered as a treatment option, our patient was offered palliative chemotherapy in view of the systemic nature of the disease.

Thus FDG PET-CT, due to its whole body screening ability, can unmask unusual metastatic sites at initial presentation and can help in reducing inappropriate surgeries in these patients.

References

[1] Mountain CF. Revisions in the international system for staging lung cancer. Chest 1997; 111: 1710-17.

[2] Pantel K, Izbicki J, Passlick B, et al. Frequency and prognostic significance of isolated tumour cells in bone marrow of patients with non-small cell lung cancer without overt metastases. Lancet 1996; 347: 649-53.

[3] Mavi A, Lakhani P, Zhuang H, Gupta NC, Alavi A. Fluorodeoxyglucose-PET in characterizing solitary pulmonary nodules, assessing pleural Pleural
Pleural refers to the pleura or membrane that enfolds the lungs.

Mentioned in: Pneumothorax


pleural

emanating from or pertaining to the pleura.
 diseases, and the initial staging, restaging, therapy planning, and monitoring response of lung cancer. Radiol Clin North Am 2005; 43: 1-21.

[4] Sridhar KS, Rao RK, Kunhardt B. Skeletal muscle metastases from lung cancer. Cancer 1987; 59: 1530-4.

[5] McKeown PP, Conant P, Auerbach LE. Squamous cell carcinoma squamous cell carcinoma
n.
A carcinoma that arises from squamous epithelium and is the most common form of skin cancer. Also called cancroid, epidermoid carcinoma.
 of the lung: an unusual metastasis to pectoralis muscle. Ann Thorac Surg 1996; 61: 1525-6.

[6] Di Giorgio A, Sammartino P, Cardini CL, et al. Lung cancer and skeletal muscle metastases. Ann Thorac Surg 2004; 78: 709-11.

[7] Eisenstein R, Kuettner KE, Neapolitan C, et al. The resistance of certain tissues to invasion. Am J Pathol 1975; 81: 337-48.

[8] Sorgente N, Kuettner KE, Soble LW, et al. The resistance of certain tissues to invasion: II. Evidence for extractable factors in cartilage which inhibit invasion by vascularized mesenchyme mesenchyme /mes·en·chyme/ (mez´eng-kim) the meshwork of embryonic connective tissue in the mesoderm from which are formed the connective tissues of the body and the blood and lymphatic vessels.  Lab Invest 1975; 32: 217-22.

[9] Earnest F, Ryu JH, Miller GM, et al. Suspected non-small cell lung cancer: incidence of occult brain and skeletal metastases and effectiveness of imaging for detection--pilot study. Radiology 1999; 211: 137-45.

[10] Weder W, Schmid RA, Bruchhaus H, et al. Detection of extrathoracic metastases by positron emission tomography in lung cancer. Ann Thorac Surg 1998; 66: 886-93.

[11] Pieterman RM, van Putten JWG, Meuzelaar JJ, et al. Staging of non-small-cell lung cancer with positron-emission tomography. N Engl J Med 2000; 343: 254-61.

[12] MacManus MP, Hicks RJ, Matthews JP, et al. High rate of detection of unsuspected distant metastases by PET in apparent stage III non-small-cell lung cancer: implications for radical radiation therapy. Int J Radiat Oncol Biol Phys 2001; 50: 287-93.

[13] Lardinois D, Weder W, Roudas M, et al. Etiology of solitary extrapulmonary positron emission tomography and computed tomography findings in patients with lung cancer. J Clin Oncol 2005; 23: 6846-53.

[14] Stinchcombe TE, Socinski MA, Gangarosa LM, Khandani AH. Lung cancer presenting with a solitary colon metastasis detected on positron emission tomography scan. J Clin Oncol 2006; 24: 4939-40.

[15] Nguyen BD, Roarke MC. Choroidal cho·roi·dal
adj.
Of or relating to the choroid.



choroidal

pertaining to or emanating from the choroid.


choroidal hypoplasia
 and extraocular muscle metastases from non-small-cell lung carcinoma: F-18 FDG PET/CT imaging. Clin Nucl Med 2008; 33: 118-21.

Nilendu C. Purandare, Venkatesh Rangarajan, Conjeevaram S. Pramesh, Anshu Rajnish, Sneha Shah and Sumeet G. Dua

Bioimaging Unit, Tata Memorial Hospital, Mumbai, Maharshtra 400012, India

Corresponding address: Dr Venkatesh Rangarajan, Bioimaging Unit, Tata Memorial Hospital, E. Borges Road, Parel, Mumbai, Maharshtra 400012, India.

Email: drvrangarajan@gmail.com

Date accepted for publication 22 October 2008
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Title Annotation:positron emission tomography; fluorodeoxyglucose; computed tomography
Author:Purandare, Nilendu C.; Rangarajan, Venkatesh; Pramesh, Conjeevaram S.; Rajnish, Anshu; Shah, Sneha;
Publication:Cancer Imaging
Article Type:Case study
Geographic Code:1USA
Date:Jan 1, 2008
Words:1407
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