Tumors of Uncertain Differentiation
Tumors of uncertain differentiation include benign and malignant neoplasms with distinctive features but uncertain lineage. Many have consistent genetic aberrations, and this category includes an increasing number of translocation-associated benign soft tissue tumors and sarcomas. Although they sometimes express antigens more characteristic of specific tumor types, such as carcinoma or melanoma, these neoplasms usually do not correspond to any normal cell type and can be regarded as new lineages with characteristic patterns of gene expression. Translocation-associated soft tissue sarcomas, when they have a reciprocal translocation resulting in diploid cells, typically lack nuclear pleomorphism, yet they often are aggressive high-grade sarcomas.
- Fetsch JF, Laskin WB, Michal M, Remotti F, Heffner D, Ellis G, et al. Ectopic hamartomatous thymoma: a clinicopathologic and immunohistochemical analysis of 21 cases with data supporting reclassification as a branchial anlage mixed tumor. Am J Surg Pathol. 2004;28:1360–70.PubMedCrossRefGoogle Scholar