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Mixed tumors with follicular differentiation: complex neoplasms of the primary epithelial germ
1Department of Dermatology, University Hospital, Salamanca, Spain.
Background:
Some mixed tumors of the apocrine variety also show characteristics of follicular and/or sebaceous differentiation. This can be explained because of the common embryologic origin of the three structures in the primary epithelial germ of the superficial ectoderm.
Methods:
Twenty specimens of apocrine mixed tumors were studied by conventional microscopy. The specimens were evaluated searching for some features of folliculo-sebaceous differentiation.
Results:
Certain features of folliculo-sebaceous differentiation were found in 45% of the samples examined. Additionally, different tumoral architectures were observed, resembling several well-characterized adnexal organoid neoplasms. In some tumors, there were also follicular structures of mesenchymal origin, similar to the dermal hair papilla and the arrector pili muscle.
Conclusion:
Apocrine mixed tumors of the skin illustrate the ability of pluripotential primordial cells to differentiate in different directions within an individual tumor. Moreover, mixed tumors appear as a compendium of different folliculo-sebaceous neoplasms. We suggest that these proliferations should be interpreted as "complex neoplasms of the primary epithelial germ."