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- 小脑肿瘤
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I could not come up with a straight forward diagnosis on this interesting case. A question first - is there associated cerebellar parenchyma resected for examination. My impression is that this is predominantly a fourth ventricular tumor, but would like to see the interface between tumor and surrounding parenchyma. There are two apparent cellular components in this tumor - (1) small cells in irregular aggregates, and (2) larger cells in between small cell aggregates.
At least some of the small cell aggregates are associated with blood vessels, suggesting that they may be perivascular lymphocytes (I do not see mature plasma cells). However, many aggregates are large and irregular shaped, and they contain cells with round as well as elongated nuclei (Figure 3). Stretching my imagination, I even see possible rosette formation in Figures 6 and 8. Some of the small cells in Figure 11 are very primitive in appearance. These features strongly suggest an embryonal cell component in this tumor.
The larger cells between small cell aggregates show fibrillary cellular processes consistent with glial (astrocytic) differentiation in many areas (Figures 3~6). In other areas (Figures 9~11), however, these cells have smaller, uniform and oval nuclei with much less prominent fibrillary cytoplasm. These uniform cells may be bland astrocytes or small mature neurocytes. Focally they appear transitional between the small cells and larger cells.
I do not see large ganglionic cells, strap cells (rhabdomyoblasts), papillary architecture, large anaplastic cells, metaplastic fat, necrosis or obvious mitotic figures. The observed features are not consistent with the classic or other variants of medulloblastoma. It is possible that this was a medulloblastoma that has undergone glial (astrocytic) and neurocytic differentiation with time before becoming symptomatic. Without additional information, the best category I can place this neoplasm in is "mixed glioneuronal tumor". This term is not formally used in WHO 2000 classification, but has been used to encompass some composite tumors showing both neuronal and glial differentiation and yet not fitting any well-defined entity. Grading of such neoplasms is variable (grade II~IV).
Immunohistochemistry (GFAP, CD56, synaptophysin, NSE, MIB-1) would help characterize various cell types in this interesting neoplasm.
聞道有先後,術業有專攻
非常高兴而且怀着浓厚的兴趣地翻译了马老师的帖子，触摸到了老师的诊断思路，感觉出了老师病理诊断的功力，通过老师丝丝入扣的分析，不但了解了该肿瘤的诊断，更带来诊断的思路。
本例非常有趣，但是有几个问题需要弄明白才好说话。首先，送检的病理标本是大脑实质吗？我的印象好象是四脑室肿瘤，但是并没有看到肿瘤和周围脑实质之间有表面之脑组织。第二个问题是肿瘤中有两种细胞成份，1是不规则排列的小细胞团，2是小细胞团之间的大细胞，至少有些小细胞与血管有关系，提示可能是血管周围的淋巴细胞（我没有看到成熟之浆细胞），许多细胞团大并且呈不规则形，有圆有长的细胞核（图3）。
尽我的想像力吧，我似乎看到了图6和8的菊形团，图11中某些小细胞形态非常幼稚（原始），这些特点明显提示为肿瘤的胚胎成份。小细胞团之间的大细胞显示出纤细之胞突，并且在许多区域显示出有胶质细胞（星形细胞）分化（图3-6），图9-11显示细胞较小，较一致，卵圆形的核，也没有明显的胞突。这些较一致的细胞，感觉是形态较温和之星形细胞或者是小的成熟神经原细胞。局部小细胞和大细胞之间有相互转化。
尽我的想像力吧，我似乎看到了图6和8的菊形团，图11中某些小细胞形态非常幼稚（原始），这些特点明显提示为肿瘤的胚胎成份。小细胞团之间的大细胞显示出纤细之胞突，并且在许多区域显示出有胶质细胞（星形细胞）分化（图3-6），图9-11显示细胞较小，较一致，卵圆形的核，也没有明显的胞突。这些较一致的细胞，感觉是形态较温和之星形细胞或者是小的成熟神经原细胞。局部小细胞和大细胞之间有相互转化。
我没有看到神经节细胞、球拍状细胞（横纹肌母细胞）、乳突状结构、大的间变性细胞、化生的脂肪组织、坏死，也没有看到明显的核分裂。
综上所述，这些特点并不足以诊断为经典之髓母细胞瘤，也不能确诊为其亚型。可能是髓母细胞瘤很早就已经向胶质细胞（星形细胞）和神经原细胞分化了，在没有其它信息的情况下，我考虑本例可能是混合性胶质神经原性肿瘤，该名称仅见于2000年以后的WHO分类，适用于复合性肿肿瘤，当肿瘤显示有神经原细胞和胶质细胞分化时可用该名称。混合性胶质神经原性肿瘤不适用于任何形态单一而十分明确的肿瘤，混合性胶质神经原性肿瘤分级从1-IV级不等。
免疫组化GFAP, CD56, synaptophysin, NSE, MIB-1都有帮助。
免疫组化GFAP, CD56, synaptophysin, NSE, MIB-1都有帮助。
