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Skeletal muscle metastases as the initial manifestation of an unknown primary lung cancer detected on F-18 fluorodeoxyglucose positron emission tomography/computed tomography
Address for correspondence: Dr. Anish Bhattacharya, Department of Nuclear Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh - 160 012, India. E-mail: anishpgi@yahoo.co.in
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This article was originally published by Medknow Publications & Media Pvt Ltd and was migrated to Scientific Scholar after the change of Publisher.
Abstract
Skeletal muscle metastasis as the initial presentation of the unknown primary lung cancer is unusual. A 65-year-old male patient presented with pain and swelling of the right forearm. Fine needle aspiration of the swelling revealed metastatic squamous cell carcinoma. The patient underwent whole body F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) to identify the site of the primary malignancy. The authors present PET/CT images showing FDG-avid metastases to the skeletal muscles along with a previously unknown primary tumor in the right lung, in a patient presenting with initial muscular symptoms without any pulmonary manifestations.
Keywords
F-18 fluorodeoxyglucose
lung cancer
metastases
muscle
positron emission tomography/computed tomography
INTRODUCTION
Skeletal muscle metastasis as the initial presentation of an unknown primary lung cancer is unusual. F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) imaging is useful in the identification of primary in carcinoma of unknown origin. We describe a patient showing FDG-avid metastases to the skeletal muscles along with a previously unknown primary tumor in the right lung, in a patient presenting with initial muscular symptoms without any pulmonary manifestations.
CASE REPORT
A 65-year-old male presented with pain and swelling of the right forearm. Fine needle aspiration cytology of the swelling showed metastatic squamous cell carcinoma. The patient underwent a whole body F-18 FDG PET/CT to identify the site of the primary malignancy. Increased FDG avidity (standardized uptake value [SUVmax] 9.0) was detected in an irregular heterogeneously enhancing soft-tissue mass in the right paravertebral region in the upper lobe of the right lung with a focus of calcification within the mass [Figure 1b and d, white arrow]. Abnormal FDG uptake was also noted in a presacral mass [Figure 1c and e], the bulky left adrenal gland, several dorsal vertebrae and multiple lesions in the trapezius [Figure 1b and d, red arrow], right brachioradialis [Figure 2], deltoid, and right external oblique muscles [Figure 3], suggestive of metastatic involvement. A diagnosis of primary squamous cell carcinoma of the lung was pathologically confirmed. The patient was treated with 4 cycles of chemotherapy, after which significant decrease in FDG uptake (SUVmax = 5.1) was seen in the primary as well as the right brachioradialis muscle lesion (not shown here).
DISCUSSION
Skeletal muscles are uncommon site of hematogenous metastases from epithelial neoplasms. Solitary muscle metastasis has been previously reported in lung cancer.[1] Tuoheti et al. found that only 4 patients (0.16%) among 2,557 patients with lung cancer developed metastasis to the skeletal muscle.[2] Most frequent muscle involvement is seen in the thigh, iliopsoas and paraspinous muscles.[3] Whole-body FDG PET/CT imaging is useful in detection of muscle metastases in lung cancer patients.[4] Multiple muscle metastases from lung cancer are rare, and FDG PET/CT imaging is useful in the identification of unsuspected metastatic sites.[5] Primary presentation of a skeletal muscle metastasis, such as in our case, remains an unusual occurrence.[36789] The present case, where the initial presentation was of metastatic muscular involvement, highlights the role of FDG PET/CT in tracing the location of primary lung malignancy and unsuspected sites of multiple muscle metastases in a patient with muscle metastases of unknown primary.
Source of Support: Nil
Conflict of Interest: None declared.
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