横紋筋線維を有するmedulloblastoma様腫瘍について

A POSTERIOR FOSSA TUMOR RESEMBLING MEDULLOBLASTOMA WITH CROSS STRIATED MUSCLE FIBERS: CASE REPORT AND REVIEW OF THE LITERATURE

Ｉ．緒言

　小脳medulloblastornaに関する多くの病理学的記載の中に時折珍らしい所見についての報告がなされていることに気付く。すなわちmedullomyoblastoma^1）2），teratoid tumor^3）4）5）あるいはmedulloblatomaに筋線維を合併した腫瘍^6）7）8）など特異的な症例である。これはいわゆるmedulloblastやneuroblastなどの神経外胚葉起源の腫瘍成分の中に成熟横紋筋線維，myoblast，時には平滑筋などの間葉起源の組織を混じた腫瘍である。

　我々も小児後頭蓋窩に原発した，このような珍らしい腫瘍を経験した。組織学的にmedulloblastomaに良く似た小型円形細胞と成熟横紋筋線維の二成分からなり，手術的に亜全摘したにもかかわらず短期間に再発死亡した症例で，現在までmedullomyoblastomaなどとして報告されている症例と同種の腫瘍と考えられたので，その臨床像，組織所見を今迄報告された症例と比較し検討を加えた。結論としては，この腫瘍はteratoid tumorとして区分さるべきものと考えられた。

A peculiar case of cerebellar tumor was describedin a 4-year-old boy. Although the tumor in the cerebellar vermis was subtotally resected at inital craniectomy, the patient died after second operation for recurrence of the tumor.

Over-all duration was one year and one month.

At autopsy, a dark-browinish and soft tumor of a walt nut size occupied the region of the vermis and the 4th ventricle, and infiltrated to the floor of the 3rd ventricle through the aqueduct. Multi-ple metastases were found in the left temporal lobe and in other parts of cerebral base.

Histologically, the tumor consisted of undiffer-entiated small uniform round cells with round or ovoid nuclei closely packed with chromatin and they had very small amount of cytoplasm. Mitotic figures were not present and connective tissue or reticulin fibers were not proven except for in the perivas cular areas. The second type of cells were cross striated muscle fibers and were found equally in the metastatic lesions. However, undifferentiated mesenchymal cells were not seen.

This tumor was quite resemble to so called medullomyoblastoma, and clinicopathological study of this case, as well as previously reported similar cases, indicated that these tumors were identical to embryonic tumor and should be classified as a teratoid tumor. Comments on the origin of this tumor were made with special remarks that this should be an entirely different type of tumor from medulloblastoma.