Skin is an uncommon site of metastatic disease when compared to other organs or sites in the body. Occasionally, cutaneous metastasis may be the first clinical manifestation of a clinically silent, visceral malignancy of unknown origin. Hemorrhagic cutaneous metastatic nodules usually imply a primary renal cell carcinoma, thyroid follicular carcinoma, or choriocarcinoma. 
Testicular choriocarcinoma is a highly malignant germ cell neoplasm that accounts for about 5% of testicular tumors.  Only 11 cases of cutaneous metastasis from choriocarcinoma from the testis are found in the literature. Here we present another patient with metastasis to the skin of choriocarcinoma and review all articles pertinent to the subject. [3-13]
Report of a patient
A 30-year-old male patient presented himself to the dermatologist with an ulcerated nodule on the back measuring 9 x 4 mm. The skin lesion was excised completely and submitted for histopathological examination. The suspicion of the clinician was a fungal infection.
The patient had previously been submitted to chemotherapy because of a testicular carcinoma, but no information was given about the type of the primary lesion in the testis.
Histopathological analysis of the specimen demonstrated that the skin was ulcerated and infiltrated by a neoplastic proliferation of large and atypical cells with areas of necrosis (Fig. 1). Two distinct cell populations were identified: syncytiotrophoblasts and cytotrophoblasts (Figs. 2-4). These cells were strongly positive for human chorionic gonadotropin antigen β- HGC (Figs. 5 and 6) and cytokeratin CKAE1/AE3 (Figs. 7 and 8). No positivity was obtained for α- fetoprotein, CD 30, or CD 34.
Ulcerated skin lesion with an irregular proliferation of pale cells in the dermis.
Infiltration of the skin by syncytiotrophoblasts and cytotrophoblasts.
Atypical cells are strongly positive for human chorionic gonadotropin antigen ß- HGC.
Positivity for cytokeratin CKAE1/AE3.
Testicular choriocarcinoma is a highly malignant germ cell neoplasm that accounts for about 5% of testicular tumors. These neoplasms are often small, with no enlargement of the testis. Choriocarcinoma primarily arises from the fetal (placental) trophoblasts in the setting of a molar pregnancy. Nongestational choriocarcinoma from the ovary or testis is much rarer. They are usually hemorrhagic and partially necrotic. Microscopically, these tumors show giant syncyciotrophoblastic cells with large, atypical nuclei intermingled with cytotrophoblasts, which recapitulates that seen in normal chorionic villi. The syncyciotrophoblastic cells are consistently immunoreactive for HCG (human chorionic gonadotropin) and keratin. 
Metastasis from germ cells tumors disseminate principally via the lymphatic route but choriocarcinoma is known to spread also hematogenously, and metastases of lungs, brain, and liver are common. Spread to the skin, however, is rare. [12, 13] Eleven cases of cutaneous metastasis from choriocarcinoma from the testis are found in the literature [3-13].
In 1989, a case of solitary metastasis to subcutaneous tissue from choriocarcinoma of the testis which was predominantly seminoma was reported. The authors discussed the propensity for vascular route of metastasis of this tumor as a cause for the clinical picture seen in this patient. The human beta chorionic gonadotropin tumor marker elevation to 4,200 units preoperatively fell to normal two weeks postoperatively, suggesting a solitary metastatic site with total tumor extirpation. Nevertheless, the patient received chemotherapy because the nature of the metastatic route suggested other microscopic sites of metastasis. 
In 1995, Chhieng et al. reported the rare presentation of choriocarcinoma as a cutaneous metastasis in a 23-year-old male. Subsequent clinical evaluation of this patient revealed a testicular tumor with metastases to lungs, brain, liver and kidney and increased serum levels of human chorionic gonadotropin. The patient died shortly after diagnosis due to complications of metastatic disease despite chemotherapy.  A year later, Shimizu et al. reported a case of a 22-year-old Japanese man with pure choriocarcinoma of the testis who developed skin metastases that presented as multiple reddish nodules. The patient died three months after the initial onset of skin metastasis.  Tariq et al. presented in 1998 a case of metastatic choriocarcinoma to the nasal cavity from testicular teratoma presenting with intractable epistaxis in a 32-year-old Caucasian male, who ultimately succumbed to this disease. 
In 2001, another case of a 24-year-old white male with a testicular mixed germ-cell tumor with skin metastases of choriocarcinoma was reported.  In the same year, the case of a 31-year-old man treated for a pure choriocarcinoma of the right testis with skin metastasis was presented. In his first examination a skin metastasis was found but none in any other localization. The ß- HCG level was 328 mu/mL. The diagnosis was confirmed by pathological examination of the testis after orchidectomy. During the evolution, partial remission (50%) was obtained after the third course and complete remission one month after the end of treatment.  In 2001, Ameur et al. reported the case of a 25-year-old man with a single perineal reddish nodule whose microscopic examination revealed the typical histological features of a testicular choriocarcinoma with metastases to liver and lungs. The patient died four months after the diagnosis due to complications of metastatic disease.  In 2005, a group of French authors reported a case of angioma-like tumor in a 22-year-old man whose histopathological examination showed a cutaneous metastasis of a testicular carcinoma. Testicular echography showed an intratesticular tumor, and pulmonary and abdominal CT scans showed multiple metastases. Orchidectomy and retroperitoneal lymphadenectomy were performed before general chemotherapy. The patient died 14 months after diagnosis.  Also in 2005, Sofikerin et al. presented a case of a 42-year-old white male with testicular choriocarcinoma with skin metastasis,  and in 2006 a Japanese group also reported a case of a 39-year-old man with a testicular choriocarcinoma with metastases in the lung, liver, brain, stomach, kidneys and skin. In spite of various chemotherapies, he died 17 months after operation.  A year later, Gleizal et al. reported what, according to them, was the second case of a skin metastasis of choriocarcinoma to the head and neck, and the third in which a cutaneous metastasis was the first finding at initial presentation. Their review of published reports showed that it had been described as individual firm, reddish or violaceous subcutaneous nodules with typical histological features. 
It is apparent from the literature that skin metastasis of choriocarcinoma is rare and usually occurs as a nodular lesion with the typical feature histopathologically of the primary disease. It usually is a sign of poor prognosis.
We report on a 30-year-old man who presented himself with an ulcerated nodule on the back which was diagnosed as a skin metastasis of testicular choriocarcinoma. The rarity of this finding is discussed. A review of the literature revealed only eleven cases. Skin metastasis of choriocarcinoma usually occurs as a nodular lesion with typical feature of the primary disease on histopathology. It is a sign of a poor prognosis.
Juliana Jung, M.D., is a pathologist at Hospital Erasto Gaertner, Curitiba, Brazil. José Fillus Neto is a dermatopathologist in Curitiba, Brazil. This article was reviewed by Almut Böer, M.D. Contact corresponding author via email: firstname.lastname@example.org .
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