to report a rare case of extreme leukocytosis and leukemoid reaction associated with lung sarcomatoid carcinoma ( lsc ) and increase people s awareness of the disease . a 58-year - old male patient was diagnosed with lsc ; however , after the end of the second course of chemotherapy , his white blood cells increased gradually without fever or use of medications such as granulocyte colony - stimulating factor and steroids . when a patient s white blood cells are extremely elevated , we should think of the possible causes of the tumor itself and identify it with other diseases . however , more data and evidence are still needed to find an effective adjuvant therapy for these patients . lung sarcomatoid carcinomas ( lscs ) are very rare , mostly reported in the form of case reports , and leukemoid reactions has rarely been described in patients with lsc , to the best of our knowledge . , we discuss an unusual case of extreme leukocytosis and a leukemoid reaction associated with the lsc . we summarize the relevant reports , hoping to provide some help for other clinicians when they encounter similar disease or symptoms . a 58-year - old male patient had symptoms of intermittent cough and hemoptysis with no incentives in june 2014 , and accompanying chest tightness and shortness of breath . he was first admitted to a local hospital , where computed tomography of the chest showed a left lung mass , suggesting a probability of tuberculosis . therefore , he was treated for tuberculosis , but had no significant relief of symptoms . he then visited our hospital , where he underwent computed tomography - guided biopsy ; the pathology results showed poorly differentiated adenocarcinoma ( left lung ) . he then underwent surgery for resection of the mass ; pathological examination showed poorly differentiated peripheral pulmonary carcinoma with the tumor being composed of mononuclear and multinucleated tumor giant cells with significant atypia . immunohistochemistry showed : creatine kinase ( ck ) (  ) , p63 (  ) , thyroid transcription factor ( ttf)-1 (  ) , ck18 ( + ) , napsin a (  ) , ck ( + ) , vimentin ( + ) , smooth muscle actin ( sma ) (  ) , desmin (  ) , epidermal growth factor receptor ( egfr ) ( + + ) , ki-67 ( + 60% ) , epithelial membrane antigen ( ema ) ( + ) ; the consideration is sarcomatoid carcinoma ( giant cell carcinoma ) . the patient received two courses of chemotherapy in our hospital after surgery , gemcitabine 1.4 d1and 8 + cisplatin 30 mg d14 and tolerated it well . however , the patient s white blood cells ( wbcs ) increased gradually without fever or use of medications , such as granulocyte colony - stimulating factor ( g - csf ) and steroids , after the end of the second course ( figure 1 ) , and neutrophils accounted for ~93% . while his hemoglobin and platelets were within the normal range . next , a bone marrow biopsy was performed ; the results showed myeloid and erythroid focal hyperplasia and significant partial immature myeloid cell proliferation ( figure 2 ) . immunohistochemistry showed individual lymphocytes cd3 ( + ) , individual lymphocytes cd20 ( + ) , erythroid cd235a ( + ) , megakaryocytes cd61 ( + ) , cd34 (  ) , individual monocytes cd14 ( + ) , individual plasma cells cd138 ( + ) , a large number of myeloid myeloperoxidase ( mpo ) ( + ) ( figure 3 ) . finally , the patient was diagnosed with leukocytosis , then he and his family refused further chemotherapy , so we put the patient on  hydroxyurea  to control the leukocytosis . this study was approved by the ethics committee of the affiliated cancer hospital of zhengzhou university . sarcomatoid carcinoma is a poorly differentiated malignant cancer , which is composed of both carcinomatous and sarcomatous elements . it can occur in many parts of the body , but most commonly affects the respiratory tract , lungs , breasts , and kidneys . clinically , sarcomatoid carcinoma originating in the lung ( lsc ) is very rare , accounting for 0.3%4.7% of all lung malignancies.1 lsc is a non - small - cell lung carcinoma , which has a high degree of malignancy , and is more aggressive than the average lung cancers . the effects of radiotherapy and chemotherapy are not very good ; therefore , the prognosis of lsc is poor.24 leukemoid reaction is defined as a wbc count > 5010/l without evidence of leukemia or infection.5 leukemoid reaction is a potential cause for leukocytosis , especially in the presence of predominately mature granulocytic leukocytosis . a leukemoid reaction is caused by an exaggerated myeloid ; it has been associated with infections , allergies , burns , intoxications , acute hemorrhage , malignant neoplasms , and several other stimuli.69 lsc associated with leukemoid reaction is very rare . cancer - related symptoms , may be caused by g - csf secreted by the tumor cells.1012 chen et al13 indicated that , in cases of leukemoid reaction , leukocytosis is frequently mediated by tumor - related cytokines and csf including g - csf , granulocyte - macrophage csf , interleukin 6 or 1. jardin et al14 have reported a case with lung sarcoma and leukemoid reaction . the patient s g - csf concentration increase was observed after the first cycle of chemotherapy ( > 20,000 pg / ml ) . dramatically , the highest g - csf concentration level was observed when the wbc count was lowest , suggesting that a massive cytokine release appeared after tumor lysis related to chemotherapy.14 we also observed a similar phenomenon in our report ; after chemotherapy , the patient s wbc experienced dramatic increases . for various reasons , we have not measured g - csf concentration level , but we can speculate that perhaps the reason was the same . leukemoid reaction always indicates a high degree of malignancy , high probability of metastasis , and recurrence and wretched prognosis . in our report , the patient died of multiple organ failure 2 months after being diagnosed with leukocytosis . this is consistent with other reports correlating leukemoid reactions with advanced and aggressive tumor cell growth and poor outcome.6,15 in conclusion , lsc associated with leukemoid reaction is very rare and the prognosis is poor . when a patient s wbc is extremely elevated , we should think of possible causes of the tumor itself and identify it with other diseases . however , more data and evidence are still needed to find an effective adjuvant therapy for these patients .