Dramatic response of chemotherapy for cancer of unknown primary origin of sarcomatoid carcinoma producing granulocyte colony-stimulating factor

Cancer of unknown primary origin (CUP) which is usually diagnosed based on the histological type of metastatic site has marked heterogeneous characteristics. Sarcomatoid carcinoma defined as CUP has not been reported according to our literature survey. A 59-year-old man presented with enlarged multiple thoracic lymph nodes, huge splenomegaly and nodules in left temporal lobe of the brain. The histopathological diagnosis of lymph node and spleen was sarcomatoid carcinoma. However, all extensive diagnostic examinations could not detect a site of primary origin. The laboratory data showed marked leukocytosis with increased serum granulocyte colony-stimulating factor (G-CSF). Therefore, the patient was finally diagnosed of CUP of sarcomatoid carcinoma producing G-CSF. After gamma knife treatment for brain metastases, two regimens of taxan-based chemotherapy (carboplatin and paclitaxel, gemcitabine and docetaxel) were administered, with no effect but further tumor progression. Splenectomy for avoiding splenic rupture was performed. As the third line chemotherapy, the combination consisting of doxorubicin and ifosfamide was administered and showed a good therapeutic effect and normalized white blood cell count and serum G-CSF level. He achieved complete remission after three cycles. Herein we present an extremely rare case of CUP of sarcomatoid carcinoma producing G-CSF. Our case suggests the importance of chemotherapy including doxorubicin and ifosfamide, and multimodal therapeutic strategy for this aggressive disease.