Light and Electron Microscopy Comparison of Poorly Differentiated Tumor

Poorly differentiated carcinoma is not a classification of tumors corresponding to adenocarcinoma, squamous cell carcinoma, or adeno-squamous carcinoma. Some textbooks classify these poorly differentiated and indistinguishable tumors as small cell carcinomas. According to the latest pathological classification of the World Health Organization (WHO) system, small cell carcinomas are one of neuroendocrine tumors, which corresponds to large cell carcinoma and so on. However, not all poorly differentiated and indistinguishable tumors are neuroendocrine tumors. Therefore, these morphologically indistinguishable low-differentiation tumors are classified as poorly differentiated carcinomas according to the degree of differentiation. The characteristics of poorly differentiated carcinomas include small cell body, large nucleo-cytoplasmic ratio, loose nuclear chromatin mainly dominated by euchromatin, large and prominent nucleolus, less cytoplasm, less various organelles, less free ribosomes, and light staining overall, which are not as strongly basophilic as other tumor cells. The cell attributes require pathological immunohistochemical analysis or genetic diagnosis. Morphologically, it only needs to indicate “suspected tumor cells” or “suspected poorly differentiated tumor cells.” And further examinations are needed to clarify the cell attributes. Such tumor cells may be poorly differentiated adenocarcinoma, poorly differentiated squamous cell carcinoma, or other cancers.