Abstract
Background. Cellular schwannomas are characterized by a high density of spindle cells, as in the Antoni A pattern. Case. A 65-year-old female was referred to our hospital for an evaluation of back pain. A CT scan showed a giant tumor, 12 cm in size, superior to the right crus of the diaphragm. An FDG-PET scan revealed abnormally increased FDG uptake in the tumor. A malignant tumor was suspected, so the tumor was resected. The tumor was encapsulated, with a smooth peripheral sheath, and was strongly adherent to the vertebrae and descending aorta. The histological examination showed that the spindle cells had a high-density arrangement with the accumulation of foamy macrophages. Immunohistochemical staining showed that the spindle cells were positive for the S-100 protein and the Ki-67 labeling index was low. The final diagnosis was a cellular schwannoma. Conclusion. We herein report a case of a giant cellular schwannoma originating from the phrenico-costal sinus. Discriminating the schwannoma from a malignant soft tissue tumor was required, because the lesion showed an abnormally increased FDG uptake due to its high cell density.
