Mixed tumor explained

A mixed tumor is a tumor that derives from multiple tissue types.^[1] A biplastic tumor or biphasic tumor has two tissue types.^{[2] [3]}

True versus false

• A true mixed tumor contains multiple types of neoplastic cells.^[4] Some sources require the included tissue types to be neoplastic for the definition of mixed tumor.^[1]
• A "false" mixed tumor contains one type of neoplastic cells, but which have more than one appearance. For example, benign pleomorphic salivary gland tumors may have some tumors cells that form pseudocartilage. Yet, all the tumor cells have similar myoepithelial profile on immunohistochemistry, and are thus classified as one cell type.

Reactive or adaptive changes to a tumor does not count towards a classification as mixed. Such changes include angiogenesis (blood vessel proliferation) and/or desmoplasia (proliferation of connective tissue).^[5]

Number of cell types

• A biplastic tumor or biphasic tumor consists of two tissue types.^{[2] [3]}
• A teratoma is the main tumor type that often includes more than two tissue types. They may form for example hair, muscle, teeth, and/or bone.^[6]

Examples of true mixed tumors

Disease	Cellular elements
Fibroadenoma^[7]		Stroma
Ceruminous adenoma^[8]	Inner luminal secretory cells	Myoepithelial cells
Carcinosarcoma^[9]	Carcinomatous cells	Sarcomatous cells

Notes and References

1. Web site: mixed tumor. TheFreeDictionary (by Farlex). 2020-04-26. In turn citing:
   -For requiring neoplastic types: Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition
   - Without further specification:
   - Farlex Partner Medical Dictionary
2. For "biplastic tumor": Salati SA. Breast fibroadenomas: a review in the light of current literature. . Pol Przegl Chir . 2020 . 93 . 1 . 40–48 . 33729177 . 10.5604/01.3001.0014.5676 .
3. For "biphasic tumor": Santosh. Arvind Babu Rajendra. Histogenetic Concepts, Terminology and Categorization of Biphasic Tumours of the Oral and Maxillofacial Region. Journal of Clinical and Diagnostic Research. 8. 2. 266–70. 2014. 2249-782X. 10.7860/JCDR/2014/7506.4078. 24701553. 3972583.
4. Fowler. Melissa H. Fowler. Jason. Ducatman. Barbara. Barnes. Leon. Hunt. Jennifer L. Malignant mixed tumors of the salivary gland: a study of loss of heterozygosity in tumor suppressor genes. Modern Pathology. 19. 3. 2006. 350–355. 0893-3952. 10.1038/modpathol.3800533.
5. Miller. Daniel D. Emley. Andrew. Yang. Shi. Richards. Joanna E. Lee. Jung Eun. Deng. April. Hoang. Mai P. Mahalingam. Meera. Mixed versus pure variants of desmoplastic melanoma: a genetic and immunohistochemical appraisal. Modern Pathology. 25. 4. 2011. 505–515. 0893-3952. 10.1038/modpathol.2011.196. free.
6. Web site: NCI Dictionary of Cancer Terms. National Cancer Institute. 20 December 2017. 2011-02-02.
7. Book: Tavassoli, F.A. . Devilee, P. . World Health Organization Classification of Tumours: Pathology & Genetics: Tumours of the breast and female genital organs . IARC Press . Lyon . 2003 . 978-92-832-2412-9 .
8. Ceruminous adenomas: a clinicopathologic study of 41 cases with a review of the literature. Thompson LD, Nelson BL, Barnes EL . Am J Surg Pathol. Mar 2004. 28. 3. 308–18. 15104293. 10.1097/00000478-200403000-00003.
9. Web site: Pathology of True Malignant Mixed Tumor (Carcinosarcoma). M Sherif Said. Medscape. Updated: Dec 01, 2015