Introduction
Lung and bronchus cancer is the third leading cancer in the United States (US) and was the leading cause of cancer death in 2019.1 Deaths from lung and bronchus cancer also accounted for 23% of all deaths related to cancer.2Lung cancer is split up into four major types of lung cancer that account for 88% of primary lung cancer; adenocarcinoma, squamous cell, small cell, and large cell, listed in descending order.3 These non-small cell lung cancers (NSCLC) makes up the majority of all lung cancers, however presentations of these cancers range from a peripheral nodule, central mass, to widely disseminated disease.3 The presentation of lung cancer can sometimes be easily seen when incidentally found on imaging, other times it is more subtle, like when presenting as a Paraneoplastic syndrome. These syndromes can present as hypercalcemia (squamous cell), SIADH (small cell), gynecomastia (large cell), or even connective tissue syndromes such as clubbing and hypertrophic osteoarthropathy (HOA) which are both most often associated with NSCLC.20
In this article, we describe a patient who experienced joint pain in her hands and pain in one knee, which later progressed to her other leg. She was ultimately found to have NSCLC of squamous origin. A thorough literature review on NIH Database has shown multiple case studies that show the correlation between NSCLC and HOA involving large joints. However, there are limited reports of singular joint involvement with later progression to other joints. One case report showed a patient with NSCLC who had 2 weeks of acute joint pain in all four extremities, including his hands, fingers, knees, and ankles and was found to have adenocarcinoma.4 Another retrospective study by Cantini and associates did a study from the years 2000 to 2005 which included patients with isolated knee monoarthritis as the initial presenting sign.5 The study eventually found that five out of 296 patients with isolated knee monoarthritis were found to have NSCLC.5 This conclusion was again demonstrated in 2020 by a case report involving monoarthritis in the knee, a presenting sign of HOA associated with NSCLC. However, the patient evaluated in this article shows that this monoarthritis could spread to other joints, which emphasizes the importance of watching for spreading arthropathies as a presenting symptom of NSCLC and how surgery could be the definitive treatment.