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Biphenotypic Branchioma: A Better Name Than Ectopic Hamartomatous Thymoma for a Neoplasm with HRAS Mutation

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Abstract

Ectopic hamartomatous thymoma is a rare neck lesion originally thought to represent a non-neoplastic hamartoma, even though thymic origin has been questioned, and there is uncertainty about whether the lesion is a neoplasm. We investigated the genetics by performing targeted next generation sequencing (NGS). Three cases were identified from the authors’ consultation files. A custom, targeted NGS panel including 1385 pan-cancer‐related genes was performed on all cases. Three patients included 2 males and 1 female, aged 50, 58 and 70 years, respectively (mean 59.3 years), with tumors arising in the low anterior neck. All cases showed classical histologic features of EHT, with one case showing intraductal carcinoma in association with the EHT. By targeted NGS, one case harbored a hotspot HRAS mutation (p.Gln61Lys), while the other two cases only showed non oncogenic variants. Dual mesoderm and endoderm derivation/differentiation (biphenotypic) has been previously recognized, with epithelial and myoepithelial components, and arising from the apparatus contributing to neck development (branchial apparatus). Thus, EHT has been shown to have genetic alterations in HRAS. These findings, without evidence of thymic derivation or an ectopic tissue location, strongly support that EHT is a true neoplasm. The name biphenotyic branchioma more correctly reflects the true nature of this dual mesoderm and endoderm derived tumor occurring in the lower neck.

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Acknowledgements

The views expressed are those of the authors solely and do not represent endorsement from Southern California Permanente Medical Group or the University of Texas Southwestern Medical Center.

Funding

This study was funded in part by the Jane B. and Edwin P. Jenevein M.D. Endowment for Pathology at UT Southwestern Medical Center.

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Authors and Affiliations

  1. Department of Pathology, Southern California Permanente Medical Group, Woodland Hills Medical Center, 5601 De Soto Avenue, Woodland Hills, CA, 91365, USA

    Lester D. R. Thompson

  2. Department of Pathology, University of Texas Southwestern Medical Center, Dallas, TX, USA

    Jeffrey Gagan & Justin A. Bishop

  3. Trinity Pathology Associates, Tyler, TX, USA

    Antoine Washington

  4. ProPath, Dallas, TX, USA

    Rodney T. Miller

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  1. Lester D. R. Thompson
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  2. Jeffrey Gagan
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  3. Antoine Washington
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  5. Justin A. Bishop
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Corresponding author

Correspondence to Lester D. R. Thompson.

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All authors declare that he/she has no conflict of interest as it relates to this research project.

Ethical Approval

All procedures performed in this retrospective data analysis involving human participants were in accordance with the ethical standards of the institutional review board (IRB #5968), which did not require informed consent.

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Thompson, L.D.R., Gagan, J., Washington, A. et al. Biphenotypic Branchioma: A Better Name Than Ectopic Hamartomatous Thymoma for a Neoplasm with HRAS Mutation. Head and Neck Pathol 14, 884–888 (2020). https://doi.org/10.1007/s12105-020-01132-4

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  • DOI: https://doi.org/10.1007/s12105-020-01132-4

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