We report about a 14-year-old boy who presented with an anterior mediastinal mass that was diagnosed as malignant teratoma. Surgical resection was performed along with pre- and postoperative chemotherapy. Although elevated alpha-fetoprotein became negative, he experienced pain in his right hip joint 3 months after resection. Systematic evaluation revealed multiple locations of metastasis, and the pathological diagnosis based on bone biopsy was malignant melanoma originating from malignant teratoma, which rapidly progressed. He died 15 months after diagnosis of the original malignant teratoma. Diagnosing and treating malignant transformation of teratoma, including malignant melanoma, is difficult because it is very rare. To our knowledge, this is the second reported case of malignant melanoma arising from a mediastinum malignant teratoma, with both cases having a poor prognosis. In addition to the follow-up of tumor markers, systematic evaluation, including imaging, should be considered even after remission to monitor malignant transformation of teratoma. We expect to establish a successful therapy and improve mortality rate after more such cases are accumulated.
Primary mediastinal germ cell tumors (GCTs) are rare and account for approximately 5% of all extragonadal GCTs. In addition, they account for approximately 25% of mediastinal tumors in children, including 60% of mature teratoma, 20% of mixed GCTs, and 20% of embryonal carcinoma (including seminoma/germinoma, immature teratoma, yolk sac tumor, and choriocarcinoma) [
However, here, we report about a patient with mediastinum malignant teratoma who could not be saved despite surgical resection and pre- and postoperative chemotherapy because of the metastasis of malignant melanoma arising from a teratoma.
A 14-year-old boy, who was initially examined for continuous coughing, was referred to our hospital owing to an anterior mediastinal mass identified on chest X-ray (Figure
Chest X-ray showing an anterior mediastinum mass.
Pathology of the extracted tumor: the image shows the mediastinal tumor resection tissue (19 × 13 × 11.5 cm in size). The surface is covered with a membrane, and the boundary is clear and shows expansive development. Approximately two-thirds of the cut surface show hemorrhaging and necrosis, including the cystic area of grayish white or black color. The remaining tumor tissue consists of a teratoma showing epithelial/epidermal appendages, central nerve, bone/cartilage, smooth muscle, adipose tissue, gastrointestinal epithelium, and respiratory epithelium differentiation. Mesenchymal tissue, muscle/adipose tissue, cartilage, central nervous system, and ducts can be seen as undifferentiated immature components. Several yolk sac tumor lesions showing reticular structures with positive immunostaining for alpha fetoprotein can also be seen.
After 3 months of follow-up, the patient experienced pain in his right hip joint while AFP was still normal. The 99mTc-methylene diphosphonate bone scan showed increased tracer uptake at the left forehead and right hip joint (Figure
Bone scintigraphy showing multiple lesions in the left frontal bone, sternum, right superior supraclavicular fossa, and iliac bone, suggesting fractures, inflammation, or malignant cells.
Cranial bone biopsy: black lesions are observed macroscopically at the surface and in the lumen of specimen. Histologically, metastasis of large heterozygous malignant cells is observed in the medullary cavity. Tumor cells are round or polygonal, including multinucleated cells with clear nucleoli, which have melanin granules in a wide cytoplasm. The histology is consistent with malignant melanoma. Large heteromorphic cells containing melanin were found with mesenchymal spindle-shaped cells of primary immature mediastinum teratoma.
We report about an adolescent patient who died of metastatic malignant melanoma arising from a mediastinal malignant teratoma after two courses of chemotherapy without re-elevation in tumor markers, including AFP. There are few reported cases of malignant melanoma arising from ovarian cystic teratomas [
A review of cases of primary malignant melanoma of the ovary revealed that it is extremely rare and has poor prognosis [
In a review of 9 cases in which malignant melanoma originated from ovarian cystic teratomas, patients were aged 24–75 years, with an average age of 51.1 years [
Mediastinal NSGCTs are associated with hematologic malignancies such as acute megakaryoblastic and myelogenous leukemia, myelodysplasia, malignant mastocytosis, and malignant histiocytosis. A retrospective study at 11 centers in the United States and Europe found that 6% of 287 patients with primary mediastinal NSGCTs developed a hematologic disorder [
Malignant transformation of teratomas, especially malignant melanomas, is very rare, and its diagnosis and treatment are extremely difficult. Although the data are limited, the prognosis is poor, and the overall 5-year mortality rate is estimated at 90% [
The authors declare that there are no conflicts of interest regarding the publication of this article.
All authors appreciate Dr. Toru Igari for his support in pathological diagnosis. Yumi Tone deceased after contributing to this study.