choriocarcinoma is one of the malignant tumors arising from trophoblastic cells characterized by the secretion of human chorionic gonadotrophin ( hcg ) . the tumor consisted of two basic cell types : cytotrophoblast and hcg - positive syncytiotrophoblast , the typical histologic features of choriocarcinoma ( 1 - 5 ) . the serum hcg level is typically elevated , with resultant isosexual pseudoprecocity in children , and menstrual abnormalities , breast enlargement , androgenic changes , or combinations thereof , in adults ( 1 , 2 ) . it usually arises from fetal trophoblasts and rarely arises from germ cells in the testis or ovary or derives from dedifferentiation of other carcinomas ( 2 , 3 ) . the most common sites of systemic metastatic disease are lungs , liver and brain via hematogenous spread ( 1 ) . skin is a rare site for metastatic choriocarcinoma , and even more rare as the initial presenting site for the disease ( 3 - 5 ) . to the best of our knowledge , we describe a case of 52-yr - old korean female patient with cutaneous metastasis of choriocarcinoma , diagnosed from a skin biopsy that provided important diagnostic clues to the primary lesion . a 52-yr - old korean female presented with dyspnea of 2 months duration and cutaneous nodules of 1 month duration on the left side of the neck and the right side of the upper back . her past medical history was significant for behet 's disease , which had been treated with colchicine for the past 4 yr . routine blood tests showed leukocytosis with a wbc of 17,780/l , anemia with a hemoglobin of 9.4 g / dl and slightly elevated hepatic enzyme levels of got / gpt at 45/51 iu / l . chest radiography , chest and abdomen - pelvis ct revealed pleural effusion , innumerable variable sized pulmonary metastatic nodules on both lungs and multiple metastatic lesions on the liver , left adrenal gland and left kidney . a skin biopsy was performed on the nodule at the right side of upper back . at low magnification , there were several hemorrhagic foci and multiple cellular infiltrations throughout the dermis ( fig . 2a ) . at high magnification , the infiltrated tumor cells consisted of two cell types , and a biphasic pattern , in close proximity . one element had polygonal shaped , clear cytoplasm and large , irregular shaped , vesicular nuclei with prominent nucleoli , which were identified as cytotrophoblasts . the other cell population showed eosinophilic cytoplasm with cytoplasmic vacuoles and many dark nuclei , which were identified as syncytiotrophoblasts ( fig . the immunohistochemical staining for hcg antigen ( 1:600 , polyclonal rabbit , dakocytomation , denmark ) in the cytoplasm of syncytiotrophoblasts ( fig . magnetic resonance ( mr ) images of the abdomen - pelvis detected diffuse enlargement of the uterus body and a protruding mass in the uterine cavity , which was the primary origin of the tumor ( fig . her serum hcg level was 700,000 miu / ml ( upper normal limit : 10 miu / ml ) . she was referred to the gynecological oncology department , where combination chemotherapy was commenced . during combination chemotherapy , the serum hcg level has fallen off under 2.0 miu / ml and her skin lesions have almost disappeared . however , 3 months after 17 cycles , total abdominal hysterectomy and bilateral salpingo - oophorectomy were performed due to elevated serum hcg level ( 4,447.7 miu / ml ) , and she is scheduled to receive post - operative adjuvant chemotherapy . compared to other organs , skin is an uncommon site of metastatic cancer in the body as it is usually associated with a disseminated disease and grave outcome . occasionally , however , as in our case , cutaneous metastasis may be the first harbinger of a visceral malignancy of unknown origin and gives an important diagnostic clue ( 3 , 4 , 6 - 8 ) . cutaneous metastasis of a visceral malignancy has been estimated to be in the wide range of 1.4% to 10.4% according to the type of study undertaken and the site of primary tumor studied ( 6 - 11 ) . involvement of the skin is likely to be near the area of the primary tumor and in proportion to the incidence of internal malignancy . the chest , abdomen , and scalp are common anatomic sites to which metastasis localize with the back and extremities being relatively uncommon areas . breast cancer in women and lung cancer in men are the most common causes of chest metastatic lesion ( 6 - 8 ) . occasionally , a cutaneous metastatic lesion may show typical histologic features which give a decisive diagnostic clue to the primary origin . such cases include mucin - containing cells in colon cancer , bile - containing glandular structure in hepatoma , clear cells in renal cell carcinoma and , like our case , cytotrophoblasts and syncytiotrophoblasts in choriocarcinoma ( 6 ) . choriocarcinoma , in women , is often preceded by a gravid state , which is most often hydatidiform mole ( 50% ) , less frequently abortion ( 25% ) , and normal term pregnancy ( 15% ) . , it commonly arises from germ cells in the testis ( 1 - 5 ) . the gross appearance of choriocarcinoma is often dark red or purple colored and resembles that of a friable segment of placenta ( 1 ) . microscopically , it is characterized by multiple foci of hemorrhage and necrosis around the neoplastic cells , by large sheets of cytotrophoblastic and syncytiotrophoblastic cells , biphasic pattern , and by the absence of hydropic villi . the cytotrophoblasts have cuboidal shaped , pale cytoplasm and large , irregular shaped , vesicular nuclei with prominent nucleoli . the syncytiotrophoblasts show eosinophilic cytoplasm with cytoplasmic vacuoles , many hyperchromatic and pleomorphic nuclei with indistinct border , looking like multinucleated giant cells , and may form syncytial knots . the immunohistochemical staining for hcg antigen is positive in the cytoplasm of syncytiotrophoblasts but not in cytotrophoblasts ( 1 - 5 ) . other germ cell tumors such as polyembryoma , embryonal carcinoma , dysgerminoma and mixed germ cell tumor can also show hcg positive syncytiotrophoblastic cells but these tumors do not demonstrate a biphasic pattern consisting of cytotrophoblasts and syncytiotrophoblasts , as in choriocarcinoma ( 1 ) . the most common metastatic sites are , in a descending order of frequency , lung ( 60 - 95% ) , vagina ( 40 - 50% ) , vulva ( 10 - 15% ) , brain , liver ( 10% ) , kidney and spleen ( < 5% ) . although choriocarcinomas respond relatively well to chemotherapy , cutaneous metastasis is an extremely uncommon presentation and a poor prognostic sign as it is associated only with disseminated disease ( 1 - 5 ) . reported a case of cutaneous metastatic testicular choriocarcinoma where the patient died 10 days after the initiation of chemotherapy ( 4 ) . shimizu et al . also reported a case of metastatic disease to the upper back of testicular choriocarcinoma , where the patient died 3 months after the appearance of a cutaneous metastatic lesion . in their literature review , of 7 patients with metastatic choriocarcinoma to the skin , 5 patients died within 3 months after the appearance of skin metastasis ( 3 ) . reported another case of choriocarcinoma with metastasis to the chest wall , which responded well to 12 cycles of combination chemotherapy ( 5 ) . we described an extremely rare patient with metastatic choriocarcinoma presenting initially as a cutaneous lesion . the diagnosis was made from the typical histological findings of a cutaneous metastatic lesion , which was confirmed by immunohistochemical staining for hcg and from the abdomen pelvis mr images . this case highlights the importance of a histological examination of skin metastatic lesion , which can provide conclusive evidences to the diagnosis .
choriocarcinoma is one of the malignant tumors of trophoblastic cells characterized by the secretion of human chorionic gonadotrophin ( hcg ) ( 1 - 3 ) . 
 cutaneous metastasis is a rare presentation of choriocarcinoma but a poor prognostic sign because it is associated only with widespread disease ( 3 - 5 ) . 
 a 52-yr - old female complaining of dyspnea for 2 months , presented with fingertip sized erythematous nodules on the left side of the neck and the right side of the upper back of 1 month duraton . 
 she has suffered from behet 's disease since 1999 . 
 microscopic examination of a nodule of upper back demonstrated biphasic pattern of cytotrophoblasts and hcg - positive syncytiotrophoblasts , and the typical histologic features of choriocarcinoma . 
 she was referred to the gynecological oncology department . 
 after 17 cycles of combination chemotherapy , the serum hcg level has fallen from 700,000 to under 2.0 miu / ml and the skin lesions have almost disappeared . however , after 3 months , total abdominal hysterectomy and bilateral salpingo - oophorectomy were performed due to elevated serum hcg level ( 4,447.7 miu / ml ) , and she is scheduled to receive post - operative adjuvant chemotherapy .