This is a rare case of a metastatic sarcomatoid carcinoma in a patient that presentead with a clinic neurological deficit. It is a very rare tumor and poorly differentiated carcinoma that derives from epithelial tissues so it can develop in several anatomical sites and histologically is characterized by presenting epithelial and mesenchymal components [1,4,5]. The most common differential diagnosis is sarcoma and differentiation markers of epithelial lineage are used to make this distinction. Specific organ markers are also tested to determine the origin of the tumor [4,6]. Initially the hypothesis of pulmonary origin was considered, namely a lung sarcomatoid carcinoma which is a rare lung cancer that belongs to the group of non-small cell lung carcinomas (NSCLC) correspondind to only 0.1-0.3% of all lung cancers [4-10]. It usually presents as a solitary mass in the upper lobes that develops from central airways cells [4,6,7] but may also present a peripheral location [10]. Several studies have described that affects mostly men with an average of 65 years old and with a high correlation with smoking [4-7,10]. There is no specific presentation and cough and hemoptysis are the most common symptoms [4]. Differential diagnosis with other primary or secondary lung cancers is difficult and still a challenge [5,8,10]. It is a very aggressive tumor associated with low survival rates, lower than other NSCLC [4,5]. Metastasis occur by hematogenous route and the most affected organs are bone, brain and lungs [4,6]. The immunohistochemical study of the pulmonary nodule identified the presence of specific markers of the epithelial lineage such as CK7 (cytokeratin) and MMF116 characteristic of carcinomas. Although several specific organ markers were tested to establish the differential diagnosis between primary and metastatic tumor such as TTF1, Napsin-A, p40, Synaptophysin and SOX10, it was not possible to successfully determine the primary origin of the tumor that remained unknown [1-3,10]. Occurred a very aggressive clinical evolution that culminated in the patient death due to complications resulting from gastric metastatic lesions that is in agreement with literature for this type of tumor [1,5]. Markers of poor prognosis were identified in some previous studies which may indicate an even more aggressive disease at the moment of diagnosis like functional status, number of metastatic sites and increased lactic dehydrogenase, leucocytosis and neutrophilia that are systemic markers of inflammation with a role in the tumorogenesis process [1,5]. Due to their very low incidence and difficulties in diagnosis, these tumors still have a lack of clinical and pathological characterization that makes greater complementarity between different medical specialties an imperative to provide a reduction in the delay of deffining an accurate diagnosis, beucause this situation causes great anxiety and anguish to the patient and his family. Further studies and research are needed and we hope that advances in molecular biology will reduce this time and increase therapeutic options given the poor results obtained with conventional chemotherapy in these type of neoplasms [1,4].