Undifferentiated cells refers to a cell that has yet to develop into a particular cell variant. Undifferentiated stem cells are the very basic cells in biology that all other cells derive from. The very first few cells in an embryo are considered undifferentiated.
Stem cells are basically undifferentiated cells that have the unique ability to produce many different types of cell lines. By the very definition large undifferentiated carcinoma cells lack either glandular or squamous differentiation.
The term is the opposite of differentiated cells and is usually used to help describe tissue or cells that have not used paracrine cell signalling to become specialized into a particular function or structures as adult stem cells. Undifferentiated cancer cells are dangerous and often grow and spread quickly.
Published Clinical Citations
 ^ Hu, Kexiang, Feihu Zhao, and Qingkang Wang. 2013. Mechanical characterization of living and dead undifferentiated human adipose-derived stem cells by using atomic force microscopy. Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine, no. 12 (September 17). doi:10.1177/0954411913503064. https://www.ncbi.nlm.nih.gov/pubmed/24044923
 ^ Louthrenoo, W, S Boonyaratavej, R Sittiwangkul, and W Sukitawut. 1998. Anti Ro/SSA positive undifferentiated connective tissue disease in a mother with a newborn with complete congenital heart block: a case report. Journal of the Medical Association of Thailand = Chotmaihet thangphaet, no. 8. https://www.ncbi.nlm.nih.gov/pubmed/9737117
 ^ Watthanaworawit, Wanitda, Paul Turner, Claudia Turner, Ampai Tanganuchitcharnchai, Allen L Richards, Kevin M Bourzac, Stuart D Blacksell, and François Nosten. 2013. A prospective evaluation of real-time PCR assays for the detection of Orientia tsutsugamushi and Rickettsia spp. for early diagnosis of rickettsial infections during the acute phase of undifferentiated febrile illness. The American journal of tropical medicine and hygiene, no. 2 (June 3). doi:10.4269/ajtmh.12-0600. https://www.ncbi.nlm.nih.gov/pubmed/23732256.