Myofibroblastic sarcoma in meningioma: a new variant of "metaplastic" meningioma

Dedifferentiated chordoid meningioma with rhabdomyosarcomatous differentiation on the middle cranial fossa

A 46-year-old woman presented with headache and right hemiparesis. MRI demonstrated a mass in the left middle fossa. Total resection was performed. A histological examination of the tumor specimen showed several characteristic morphological features. A chordoid meningioma showing an epithelial-like palisade arrangement was observed. An anaplastic short spindle cell tumor exhibiting a fascicular pattern was considered to be a rhabdomyosarcoma. After conventional radiotherapy, the tumor was well controlled without any neurological deficit for 20 months. When subsequent recurrences were observed, the patient was treated by surgery, stereotactic radiosurgery and chemotherapy. Thirty-two months after the initial treatment, the patient died due to intracranial dissemination and an autopsy was performed. The histological examination of the recurrent and autopsy specimens showed a prominent sarcoma component. This case appears to be the first reported intracranial tumor diagnosed as a dedifferentiated chordoid meningioma with rhabdomyosarcomatous differentiation.

Anaplastic and meningothelial meningiomas in a single tumor: A "dedifferentiated meningioma"?

The patient was a 74-year-old man, who developed progressive cognitive impairment and gait instability. Neuroradiological examination demonstrated a large and predominantly extra-axial tumor spreading over the bilateral frontal base, indicative of olfactory groove meningioma. The greater part of the resected tumor consisted of a dense, patternless proliferation of large, round or polygonal cells, and compactly fascicular growth of spindle cells. Tumor cells showed markedly anaplastic cytological features. In small areas of the tumor, a typical meningothelial meningioma showing no cellular atypism was found. Both tumor components were closely juxtaposed and no pathological features of an intermediate grade (atypical meningioma) were noted. Shortly after the operation, the patient developed a local recurrence of the tumor and multiple metastases to the cerebrum, bone and skin. Anaplastic meningioma is a rare, highly malignant neoplasm which arises de novo or as a result of the progressive transformation of a low-grade meningioma. The coexistence of anaplastic and low-grade components in a single meningeal tumor has been rarely reported. This dimorphic appearance is reminiscent of "dedifferentiation", a phenomenon infrequently seen in various mesenchymal and salivary gland neoplasms. We think that the term "dedifferentiated meningioma" can be appropriately applied to tumors such as that reported herein.

Emergence of a high-grade sarcoma in a recurrent meningioma: malignant progression or collision tumor?

Anaplastic meningiomas that resemble sarcomas often reveal clues to their meningothelial differentiation or develop in a plausible setting that confirms their meningothelial origin. Malignant mesenchymal neoplasms without obvious evidence of meningothelial differentiation or origin are more likely to be true primary or metastatic sarcomas. Because of their clinical and biological differences, it is important to distinguish anaplastic meningioma from a sarcoma. We present a 67-year-old woman with multiple meningiomas, who developed a high-grade spindle cell tumor 6 months after the resection of a World Health Organization grade I meningioma. It was not clear whether this tumor represented a malignant transformation of meningioma or a primary sarcoma. Malignant transformation of a meningioma is exceptional within this short period and a coexisting sarcoma and meningioma are equally uncommon. Even though these malignant neoplasms are rare in general, they appear to be more prevalent in patients with multiple meningiomas including those with neurofibromatosis type 2.