PMC6332946_01
Chest X-ray showing an anterior mediastinum mass.
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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 1).
Pathology of the extracted tumor: the image shows the mediastinal tumor resection tissue (19 x 13 x 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.
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The pathological diagnosis of the extracted tumor was malignant teratoma with areas of yolk sac tumor (Figure 2).
Bone scintigraphy showing multiple lesions in the left frontal bone, sternum, right superior supraclavicular fossa, and iliac bone, suggesting fractures, inflammation, or malignant cells.
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The 99mTc-methylene diphosphonate bone scan showed increased tracer uptake at the left forehead and right hip joint (Figure 3).
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.
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The pathological diagnosis was metastatic malignant melanoma originating from an immature teratoma of mediastinum (Figure 4).