TIBIAL METASTASIS AS INITIAL PRESENTATION OF SQUAMOUS CELL LUNG CANCER

Abstract

TOPIC: Lung Cancer TYPE: Medical Student/Resident Case Reports INTRODUCTION: Lung carcinomas are frequently detected at stage IV and pain caused by bone metastasis - usually to the ribs and thoracic vertebrae - is a frequent manifestation. Metastasis to the lower limbs are extremely rare, particularly below the knee and as solitary lesions. CASE PRESENTATION: A 57 years-old white man, former smoker (74 pack-years) with sleep apnea, presented to his physician with 2 weeks of right atraumatic knee pain, worse on exertion. No constitutional symptoms were reported. Knee radiography was normal. Considering a rheumatological disorder, non-steroidal anti-inflammatories drugs and intra-articular steroid injection were prescribed, but without improvement. The patient then underwent knee magnetic resonance imaging, which showed a mass at the proximal tibial epiphysis extending to the tibial cortex and surrounding soft tissues (figure 1). To exclude primary malignancy of the bone, a computed tomography (CT) guided bone biopsy was made. Bone scintigraphy excluded other lesions. Two months later, the patient presented to our emergency department with hemoptysis and weight loss of 22% of his body weight in the previous 3 weeks. Physical examination revealed low-pitched vesicular murmur on the left hemithorax, as well as swelling of the inferior portion of the right knee and upper third of the right tibial and severe pain at palpation with impaired gait. Chest radiograph showed a heterogeneous opacity on the upper left lung field (figure 2), and the thorax CT revealed a large mass in the central area of the upper lobe of the left lung, extending to the hilum with mediastinal adenopathies. Adrenal and hepatic metastasis were also noted (figure 3). Bone biopsy performed (previously at another hospital), revealed a carcinoma with squamous differentiation favouring a metastatic process. Bronchial biopsy by flexible bronchoscopy revealed squamous cell lung tumor, so the diagnosis of stage IV lung cancer was made. He will start palliative bone radiotherapy shortly and, pending the programmed death ligand 1 tumor proportion score, systemic treatment with chemo or immunotherapy. DISCUSSION: Lung cancer's bone metastases are usually found in the axial skeleton. The few cases of below-the-knee metastasis described in the literature are secondary to adenocarcinoma or small cell lung cancer. In this case, the diagnosis of lung cancer was delayed mainly due to the extremely atypical presentation as knee pain without respiratory or systemic symptoms. CONCLUSIONS: Although rarely, pain due to tibial metastasis may be the initial presentation of lung cancer. Therefore, this should be taken in consideration when approaching single bone lesions or localized rheumatologic disorders in order to prevent a delay in diagnosis and treatment of lung cancer, especially in current or past-smokers. REFERENCE #1: Popper HH. Progression and metastasis of lung cancer. Cancer Metastasis Rev 2016;35(1):75-91. REFERENCE #2: Gurrieri L, Longhi A, Braghetti A. Lung cancer presenting as a metastasis to the tibial bones: A case report. Tumori 2015;101(1):e18-20. REFERENCE #3: Kurishima K, Kagohashi K, Mammoto T, Satoh H. Tibia metastasis from small cell lung cancer. Tuberk Toraks 2014;62(1):89-90. DISCLOSURES: No relevant relationships by Carolina Alves, source=Web Response No relevant relationships by José Alves, source=Web Response No relevant relationships by Maria Carolina Carvalho, source=Web Response No relevant relationships by Ana Mendes, source=Web Response No relevant relationships by Ricardo Oliveira, source=Web Response No relevant relationships by Margarida Pereira, source=Web Response