SESSION TITLE: Cancer Student/Resident Case Report Posters III
SESSION TYPE: Medical Student/Resident Case Report
PRESENTED ON: Tuesday, October 28, 2014 at 01:30 PM - 02:30 PM
INTRODUCTION: Lung cancer, the most common cancer worldwide, presents as a metastatic disease in majority of the cases. The most frequent sites of distant metastases are liver, adrenal glands, bones, and brain. Skeletal muscle metastasis as a mode of presentation of lung cancer is a rare phenomenon which is often discovered at autopsy.
CASE PRESENTATION: A 69-year-old male, with forty pack years history of smoking, presented with a painful right, distal thigh swelling for two months and unintentional weight loss of twenty pounds. Examination of right distal thigh revealed a tender, hard, non fluctuant mass, with surrounding erythema. Complete blood count, basic metabolic and hepatic function panel were unremarkable. Chest x ray showed large mass in right lower lobe with a smaller nodule in the right upper lobe which was confirmed by computed tomography ( CT) of the chest. Magnetic resonance imaging of the right lower extremity showed 5.5 x 4.0 x 6.2 cm soft tissue mass in lateral aspect of the distal thigh adjacent to femur. The patient underwent CT guided biopsies of the right lower lobe lung mass and the right thigh mass. Pathology of the lung mass revealed moderately differentiated adenocarcinoma (immunostaining positive for cytokeratin and thyroid transcription factor-1) and that of the right thigh mass revealed poorly differentiated malignant tumor most consistent with metastatic non small cell carcinoma (immunostaining positive for cytokeratin). Positron-emission tomography with 18F-fluorodeoxyglucose (FDG) demonstrated hypermetabolic right lower lobe lung mass and right upper lobe lung nodule, a large right knee soft tissue mass and multiple hypermetabolic soft tissue lesions throughout the muscles of the body along with jugular, external iliac and inguinal hypermetabolic lymphadenopathies. The patient was started on palliative radiation to the right distal thigh. Chemotherapy was not administered due to rapidly deteriorating clinical status. The patient died of septic shock within 4 weeks of diagnosis.
DISCUSSION: Skeletal muscle is an exceptionally rare site of metastasis of lung cancer(1). The local pH and the contractile property of skeletal muscle do not favor metastasis. Delay in the diagnosis may occur due to its clinical and radiological resemblance to diseases like abscess and soft tissue sarcoma. Definitive diagnosis requires biopsy of the muscle mass. Treatment is palliative, and majority of the patients die within 1 year of diagnosis (2,3)
CONCLUSIONS: Lung cancer with skeletal muscle metastasis should be considered as a potential differential diagnosis in patients presenting with intramuscular mass.
Reference #1: Belhabis D, et al. Muscle metastasis of primary bronchial carcinoma. Tunis Med. 2001;79:557-560.
Reference #2: McKeown PP, et al. Squamous cell carcinoma of the lung: An unusual metastasis to the pectoralis muscle. Ann Thorac Surg. 1996;61:1526-1528.
Reference #3: Sridhar KS, et al. Skeletal muscle metastases from lung cancer. Cancer. 1987;59:1530-1534.
DISCLOSURE: The following authors have nothing to disclose: Runa Shrestha, Rajesh Mourya, Archana Rao, Frank Paolozzi
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