尽管依靠光学显微镜能辨认出大部分肿瘤,但要依赖光镜在某些重要领域作出精细诊断仍比较困难,甚至是不可能的。例如要鉴别诊断未分化的多角细胞瘤为癌、淋巴瘤和色素缺乏性的黑色素瘤或上皮样癌便很困难。此外,梭状细胞瘤也可能是癌、黑色素瘤或鳞状上皮肉瘤;一些更特殊的肿瘤如儿童的小圆细 Although most of the tumors can be identified by optical microscopy, it is still difficult or even impossible to rely on light microscopy to make a fine diagnosis in some important areas. For example, it is difficult to distinguish between the diagnosis of undifferentiated hyperkeratotic tumors as cancers, lymphomas, and pigmentary melanomas or epithelioid cancers. In addition, the spindle cell tumor may also be cancer, melanoma or squamous epithelial sarcoma; some of the more special tumors such as children’s small round fine