Pancoast syndrome is a term used to describe unilateral shoulder and arm pain, weakness, and atrophy of hand muscles and Horner's syndrome as a result of a mass in the lung apex compressing blood vessels and nerve trunks. Bronchogenic carcinoma is the most common underlying etiology. A detailed clinical and imaging workup, as well as biopsy, is necessary to make a definite diagnosis.
Pancoast syndrome is an important clinical presentation of several disorders with different etiologies that develop in the apex of the lungs    . Bronchogenic carcinoma, however, is by far the most common cause of this clinical syndrome characterized by one or more of the following symptoms :
Although bronchogenic carcinomas are responsible for the development of Pancoast syndrome in the majority of cases (hence the terms Pancoast tumors or superior sulcus tumors), other conditions are neoplastic diseases (non-Hodgkin lymphomas, multiple myelomas, metastatic cancers of the liver and uterus), fungal infections (hydatid cysts as a result of Echinococcosis, histoplasmosis, aspergillosis, and mucormycosis) and pulmonary tuberculosis, whereas bacterial infections and other benign pathologies rarely induce Pancoast syndrome   .
As Pancoast syndrome is the likely manifestation of a malignant disease, its early recognition is vital for ensuring optimal patient outcomes. Unfortunately, tumors are already at an advanced stage when Pancoast syndrome appears (T3 or T4 stage is observed in the majority of cases) . Nevertheless, the immediate workup should start with a patient history that will note the timeline of complaints and their progression, whereas a properly conducted physical examination could identify unilateral pain of the shoulder and weakness of the ipsilateral arm, as well as constitutive features of Horner's syndrome. There should be a clinical suspicion regardless of the severity of symptoms, and imaging studies should be performed promptly, as they are the cornerstone in determining the etiology. Plain chest X-rays often reveal a homogeneous shadow or opacity in the lung apex and asymmetry of the apical caps of > 5 mm, but computed tomography (CT) is the gold standard    . CT is able to confirm the state of the surrounding tissues and determine whether the mass has invaded the ribs, vertebral bodies, the mediastinum, the brachial plexus, but also if blood vessel occlusion has occurred   . Furthermore, magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) can be employed to obtain an even better view of the tissues  . Even though bronchoscopy and subsequent biopsy of the lesion yields a definite diagnosis, the hardly accessible location of the lung apex does not allow for appropriate sampling  . For this reason, transthoracic image-guided needle aspiration biopsy has established itself as the main technique for obtaining a viable sample for histopathological examination  .