NON-SMALL CELL CARCINOMA OF LUNG WITH METASTASIS TO DELTOID MUSCLE: A RARE AND UNUSUAL PRESENTATION

Abstract

SESSION TITLE: Medical Student/Resident Lung Cancer Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Lung cancer is the leading cause of cancer-related death worldwide. Major risks factors include tobacco smoking and environmental pollution. Despite its high incidence, the lack of efficacious screening programs for early detection and presence of non-specific symptoms mimicking other respiratory diseases lead to late-stage diagnosis [1]. Lung cancer is known to metastasize to most organs, including brain, bone, liver, adrenal glands, and lymph nodes due to their abundant blood supply [2]. Metastatic spread of lung cancer to skeletal muscle, however, is an extremely rare finding seen in less than 1% of all cases [3]. Skeletal muscle metastases most commonly arise from primary tumors of the gastrointestinal and genitourinary tracts [4], with the muscles most frequently affected being the thigh, iliopsoas, and paraspinous muscles [5]. Multiple hypotheses have been formulated to explain the low prevalence of muscle metastases, which include muscle contractility, tissue pressure, variable blood flow, oxygen free-radical production, cellular and humoral immunity, and hypersensitivity reactions. CASE PRESENTATION: We are reporting a 61-year-old male presenting with left shoulder pain since motor vehicle accident, cough and weight loss. X-ray of shoulder was unremarkable. CT chest showed 10.0 x 7.4 cm mass noted in the left upper lobe concerning for neoplasm. MRI left shoulder showed significant edema involving the deltoid muscle with no drainable fluid. IR US guided deltoid biopsy showed poorly differentiated adenocarcinoma that favored the result of lung mass biopsy as well. DISCUSSION: Skeletal muscle is an extraordinarily rare site of metastasis of lung cancer and usually favors aggressive disease. Non-small cell lung cancer metastasis to skeletal muscle is seen in <1% of cases. Diagnosis is usually obtained by fine needle biopsy of muscle. Adenocarcinoma of the lung with metastatic spread to skeletal muscles described in the literature as more aggressive with median survival of approximately 6 months. The best effective treatment is currently unknown. CONCLUSIONS: Lung cancer is the most common cause of cancer related deaths worldwide, with non-small cell lung cancer (NSCLC) making up 8% of all cases. Skeletal metastatic disease is extremely rare, especially to upper extremities and if present usually affects injured muscle site.Alteration of muscle physiology increases susceptibility to cancer spread. The lactic acid producing activity of tumors has been described as a factor that contributes to the formation of new blood vessels by signaling low perfusion to an area of the body. This neovascularization produces a more hospitable environment for tumor growth. Muscle injury may decrease muscle ability to remove lactic acid. Increased vascular perfusion to injured areas has been associated with increased susceptibility for metastatic disease. Reference #1: Seely S. Possible reasons for the high resistance of muscle to cancer. Med Hypotheses. 1980;6(2):133–137. doi:10.1016/0306-9877(80)90079-1. https://pubmed.ncbi.nlm.nih.gov/7393016-possible-reasons-for-the-high-resistance-of-muscle-to-cancer/ Reference #2: Perisano C, Spinelli MS, Graci C, et al. Soft tissue metastases in lung cancer: a review of the literature. Eur Rev Med Pharmacol Sci. 2012;16(14):1908–1914. https://www.europeanreview.org/article/2667 Reference #3: Surov A, Kohler J, Wienke A, Gufler H, Bach AG, Schramm D, et al. Muscle metastasis: comparison of features of different primary tumors. Cancer imaging 2014;14:21 DISCLOSURES: No relevant relationships by Muhammad Faisal Aslam, source=Web Response No relevant relationships by Ritika Kompella, source=Web Response No relevant relationships by Luis Medina Mora, source=Web Response No relevant relationships by Anastasia Novikov, source=Web Response No relevant relationships by Theo Trandafirescu, source=Web Response No relevant relationships by Salim Yaghi, source=Web Response