About

Andrew J. Bauer, M.D., is a Professor of Pediatrics specializing in Endocrinology and Diabetes at the Children's Hospital of Philadelphia. He serves as the Medical Director of The Thyroid Center at CHOP and is involved in clinical care, particularly focusing on pediatric thyroid disease, including thyroid nodules and thyroid cancer. His research expertise encompasses pediatric thyroid disorders such as hypothyroidism, hyperthyroidism, thyroid nodules, and thyroid cancer. Dr. Bauer has contributed to the understanding of pediatric thyroid carcinoma through various publications and is engaged in collaborative clinics to treat refractory and progressive thyroid cancers in pediatric patients. His educational background includes a BS in Biochemistry from Canisius College and an MD from SUNY Buffalo School of Medicine and Biomedical Sciences.

Research topics

• Medicine
• Internal medicine
• Pediatrics
• Oncology
• Pathology

Selected publications

• Single-cell analysis reveals the cellular and transcriptional heterogeneity of the normal pediatric thyroid

  Frontiers in Endocrinology · 2026-01-29 · 1 citations

  articleOpen access

  To enhance the understanding of cellular heterogeneity within the pediatric thyroid, single-nuclei RNA sequencing was used to recover 38,069 non-pathogenic cells from thyroid tissue of three female pediatric/young adult patients. The recovered cells were analyzed using the SWANS (Single Entity Workflow ANalysiS pipeline (version 1.0). Analysis revealed seven major cell types: thyrocytes, endothelial cells, fibroblasts, C cells, T cells, B cells, and myeloid cells. Thyrocytes were the most prominent and heterogeneous cell type. Initially, two dominant thyrocyte subsets were identified based on transcriptional activity, which were subsequently subdivided into seven subclusters. Differentially expressed genes within each cluster support distinct cellular functions, including a metabolically active subset which may be involved in hormone synthesis and a subset involved in the transport of thyroid hormone into circulation. We identified an immune subpopulation originating predominantly from a single sample that was histologically and morphologically similar to the other two samples. This supports that transcriptional changes can be detected and used to identify populations of cells, even in the absence of histologically observable changes. This characterization represents the first comprehensive portraiture of pediatric thyroid gland cells and the first description of normal patient thyrocyte and stromal cell heterogeneity in the absence of adjacent malignancy.

  PublisherOA PDFDOI

• The landscape of pediatric differentiated thyroid carcinoma and predictors of invasive disease: a CATC study

  The Journal of Clinical Endocrinology & Metabolism · 2026-04-21

  articleSenior author

  CONTEXT: Differentiated thyroid carcinoma (DTC) is rare in children, comprising 2-4% of pediatric cancers. Due to low case volumes at individual institutions, comprehensive data on patient and tumor characteristics and treatment outcomes are limited. The Child and Adolescent Thyroid Consortium (CATC) was established in 2019 to address this gap and to assess impact of changes in practice on outcomes. OBJECTIVE: This inaugural CATC study analyzes the landscape of pediatric DTC and predictors of invasive disease. DESIGN: International, multicenter retrospective analysis of children (< age 19) with DTC diagnosed from 2010-2019. SETTING: Five high-volume pediatric centers. RESULTS: The cohort included 715 children (78.3% female) diagnosed with DTC at median age 15.2 years (range: 3.2-18.9). There were 673 (94%) patients with papillary thyroid carcinoma (PTC) and 42 (6%) had follicular thyroid carcinoma (FTC). Among PTC patients, Stage 1(M0) disease was present in 562 individuals (83.5%; 222 N0, 161 N1a, and 179 N1b). Stage 2 (M1) disease was present in 111 (16.5%) children with PTC and 1/42 (2.4%) with FTC. Males and children <10 years exhibited more advanced T-, N-, and M-stages. Any extrathyroidal extension (ETE) correlated with increased nodal and pulmonary metastases. Oncogenic fusions, compared with BRAFV600E, were associated with more advanced N- and M-stages. Deintensification of therapy since 2015 was not associated with changes in disease outcomes. CONCLUSIONS: Invasive DTC is associated with age <10 years, male sex, tumors driven by oncogenic fusions and ETE. Despite less aggressive therapies in recent years, disease outcomes have not worsened. Recognition of these associations may guide care and prognostication.

  PublisherDOI

• KEAP1 mutations activate the NRF2 pathway to drive cell growth and migration, and attenuate drug response in thyroid cancer

  Frontiers in Oncology · 2026-01-07

  articleOpen access

  The KEAP1/NRF2 pathway, a major regulator of the cellular oxidative stress response, is frequently activated in human cancers. Often mediated by loss-of-function mutations in KEAP1 , this activation causes increased NRF2 transcriptional activity and constitutive activation of the antioxidant response. While KEAP1 mutations have been well documented in various cancers, their presence and role in thyroid carcinoma have remained largely unexplored. In this study, we sequenced pediatric thyroid tumors and analyzed publicly available datasets, identifying 81 KEAP1 mutations in tumors across a range of histologies. In these tumors, we further identified frequent biallelic loss of KEAP1 via 19p13.2 loss of heterozygosity (LOH). MAPK-activating alterations were found in a subset of KEAP1 -mutant cases, but they were mutually exclusive with 19p13.2 LOH. Transcriptome analysis also revealed significant activation of the NRF2 pathway in KEAP1- mutant tumors. Four additional cases with similar transcriptional profiles but lacking mutational data were identified, likely representing putative KEAP1 mutants. Using in vitro cell line models, we then profiled the functional consequences of KEAP1 knockout in cells with and without known driver alterations. In these models, we show that KEAP1 loss leads to an NRF2-dependent upregulation of AKR1C3 , GCLC , NQO1 , and TXNRD1 , along with increased proliferation and migration irrespective of MAPK mutational status. We also demonstrate that loss of KEAP1 reduces sensitivity of RET fusion-positive cells to selpercatinib, consistent with previous reports that these alterations promote drug resistance in other malignancies. In this study, we comprehensively profile KEAP1 mutations in thyroid tumors, showing that they are more prevalent and functionally significant than previously recognized. These findings position KEAP1 mutations as novel oncogenic variants in thyroid cancer and support the integration of KEAP1/NRF2 pathway profiling into future studies and clinical frameworks.

  PublisherDOI

• MCT8 Deficiency in Females

  Universität Zürich, ZORA · 2026-01-01

  articleOpen access

  Context: Monocarboxylate transporter (MCT) 8 facilitates thyroid hormone (TH) transport across the blood-brain barrier. Pathogenic variants in SLC16A2 cause MCT8 deficiency (Allan-Herndon-Dudley syndrome), characterized by intellectual and motor disability and abnormal thyroid function tests. MCT8 deficiency typically affects males due to its X-linked inheritance. Objective: Here, we report 8 female patients with heterozygous pathogenic variants in SLC16A2 who presented with variable neurocognitive impairment, behavioral problems, and TH function abnormalities. Methods: We performed X-chromosome inactivation studies in female patients in whom heterozygous pathogenic variants in SLC16A2 were identified. The effect of SLC16A2 variants on TH transport was assessed in transfected cells and patient-derived fibroblasts. Results: In all patients (mean age 8.6 years; range, 2.3-25 years) routine care genetic analyses identified heterozygous variants in SLC16A2 (p.(R445C), p.(N193I), p.(G276R), t(X;20), resulting in a breakpoint in intron 1, t(X;19), resulting in a breakpoint in SLC16A2, p.(I562Sfs566*), p.(G221R)). All missense variants showed substantially reduced MCT8-mediated TH uptake in transiently transfected cells. X-chromosome inactivation studies in patient cells showed skewed X-inactivation in all 7 evaluated individuals. In 5 out of 7 evaluated cases, MCT8-mediated 3,5,3'-triiodothyronine (T3) uptake in patient-derived fibroblasts was impaired to a similar degree as in fibroblasts derived from male patients with MCT8 deficiency. Conclusion: Female patients with heterozygous pathogenic variants in SLC16A2 and skewed X-chromosome inactivation may present with variable neuro(psycho)logical, behavioral, and thyroid function test abnormalities. Female patients presenting with neurocognitive impairment and abnormal TH function tests (low free thyroxine and/or high total T3 concentrations) should be tested for genetic variants in SLC16A2.

  PublisherDOI

• Age-specific risk of malignancy in pediatric thyroid cytology: Reframing ROM based on pre-test probability

  The Journal of Clinical Endocrinology & Metabolism · 2026-02-24

  articleOpen accessSenior author

  OBJECTIVE: Paediatric thyroid nodules are uncommon but have a higher malignancy rate than adult nodules. Existing Bethesda risk-of-malignancy (ROM) estimates are not age-stratified and are affected by verification bias. We aimed to generate age-specific ROM, likelihood ratios (LRs), and post-test malignancy probabilities for paediatric and young adult thyroid cytology. METHODS: We analysed 2,728 thyroid fine-needle aspirations (FNAs) from patients aged 0-25 years across multiple tertiary centres (2000-2023). All cases were classified or reclassified using the 2023 Bethesda System and grouped into four age bands (0-8, 9-14, 15-18, and 19-25 years). We calculated lower-bound ROM (ROM overall; assuming non-operated FNAs were benign) and surgery-only upper-bound ROM (ROM surgery; 991 of 2,728 cases with histology). Age-specific pretest probabilities and Bethesda-category LRs were used to compute post-test malignancy probabilities with Bayes' theorem. RESULTS: Among operated nodules, malignancy prevalence decreased with age (84.2% at 0-8 years to 64.6% at 19-25 years). Verification bias was substantial: malignancy prevalence was 24.6% (671/2,728) under the lower-bound assumption but 67.7% (671/991) among surgical cases. Upper-bound ROM values were 2-10 times higher than lower-bound values across categories. Benign cytology showed low LRs (0.07-0.15), reducing post-test malignancy probability to 0-25%. Indeterminate categories showed age-related variation; for example, a follicular neoplasm diagnosis carried a ∼71% post-test risk in a 9-year-old versus ∼49% in a 24-year-old. AUS subtyping (nuclear vs other atypia) did not consistently separate ROM. CONCLUSIONS: Age substantially modifies both pretest and post-test malignancy probabilities in paediatric thyroid cytology. An age-stratified LR framework helps quantify verification bias and provides individualized risk estimates to guide decisions about surgery, molecular testing, and follow-up.

  PublisherDOI

• DNA Methylation-Based Risk Stratification and Classification of Pediatric Thyroid Carcinoma

  Clinical Cancer Research · 2026-02-17

  articleOpen access

  PURPOSE: Accurate assessment of invasiveness in pediatric thyroid carcinomas is essential to prevent unnecessary surgery and avoid surgery-associated complications. DNA methylation, a proven molecular biomarker for cancer classification, holds promise for stratifying thyroid cancer risk. The objectives were to determine the epigenetic hallmarks of pediatric thyroid carcinomas and investigate whether DNA methylome profiling is a feasible approach for preoperative risk stratification of this pediatric disease. EXPERIMENTAL DESIGN: We interrogated genome-wide DNA methylation profiles from two separately processed cohorts of pediatric thyroid carcinoma. The reference cohort included 100 samples, consisting of 87 well-differentiated primary tumors-77 papillary and 10 follicular thyroid carcinomas-and 13 matched lymph node metastases. To predict oncogenic drivers and tumor invasiveness, defined by the presence of nodal metastasis, we trained two classifiers on the reference cohort and then evaluated their performance on a second validation cohort of 84 samples, including 83 primary tumors and one lymph node metastasis. RESULTS: We identified distinct methylation patterns associated with tumor invasiveness and key driver mutations, including BRAF p.V600E, RAS-like mutations, kinase fusions, and DICER1 mutations. The differentially methylated regions reflect inflammatory stress and disrupted thyroid development and function, implicating androgen receptor, Hippo, and AP-1 signaling. Leveraging these epigenetic signatures, we developed and validated two methylation-based classifiers that accurately predict tumor invasiveness and oncogenic mutation subgroups. CONCLUSIONS: In patients with pediatric thyroid carcinoma, DNA methylation assays accurately predict tumor invasiveness and driver mutations. Our findings highlight the clinical value of DNA methylation profiling for risk stratification and classification of pediatric thyroid cancers.

  PublisherOA PDFDOI

• Thyroid Monitoring After Intravascular Iodinated Contrast Media in Infants and Children Through 3 Years of Age

  PEDIATRICS · 2026-04-27

  article

  In March 2022, the US Food and Drug Administration issued a drug safety communication (DSC) recommending monitoring of thyroid function in children up to 3 years of age who receive intravascular injection of iodinated contrast media (IV ICM) for medical imaging. In response, a group of pediatric and imaging experts convened to review the current scientific evidence on thyroid dysfunction after IV ICM and to provide recommendations on thyroid testing and management after IV ICM administration in infants and children. There are considerable gaps in knowledge related to the risk of thyroid dysfunction in young children exposed to IV ICM, and we strongly recommend that high-quality prospective studies be proposed and funded to clarify the incidence, risk modifiers, natural history, and outcomes of thyroid dysfunction after IV ICM exposure in this population.

  PublisherDOI

• Molecular Landscape and Therapeutic Strategies in Pediatric Differentiated Thyroid Carcinoma

  Endocrine Reviews · 2025-02-07 · 9 citations

  reviewOpen accessSenior author

  There has been significant progress in understanding the molecular landscape of pediatric differentiated thyroid carcinoma (DTC) over the past 2 decades. Classification of pediatric DFC into 3 tiers, RAS-like mutant, BRAF mutant, and kinase fusions, accurately reflects an increasing risk for invasive behavior, including regional and distant metastasis. In clinical practice, somatic oncogene testing for nodules with indeterminate cytology per the Bethesda System for Reporting Thyroid Cytopathology provides objective data to optimize surgical planning. In addition, knowledge of the somatic oncogene for widely invasive carcinomas allows for incorporation of oncogene-specific inhibitory therapy both in the adjuvant and neoadjuvant setting. In the present review, we review the risk factors, clinical presentation, and evaluation of pediatric DTC, highlighting the correlation among ultrasound features, cytology, and oncogenic driver of the tumor. We subsequently propose an integrated, multimodal approach that can be used to improve diagnostic accuracy and reliability for preoperative planning as well as identify and discuss which pediatric patients may benefit from systemic oral targeted therapy.

  PublisherOA PDFDOI

• Mapping variants in thyroid hormone transporter MCT8 to disease severity by genomic, phenotypic, functional, structural and deep learning integration

  Nature Communications · 2025-03-12 · 4 citations

  articleOpen access

  Predicting and quantifying phenotypic consequences of genetic variants in rare disorders is a major challenge, particularly pertinent for 'actionable' genes such as thyroid hormone transporter MCT8 (encoded by the X-linked SLC16A2 gene), where loss-of-function (LoF) variants cause a rare neurodevelopmental and (treatable) metabolic disorder in males. The combination of deep phenotyping data with functional and computational tests and with outcomes in population cohorts, enabled us to: (i) identify the genetic aetiology of divergent clinical phenotypes of MCT8 deficiency with genotype-phenotype relationships present across survival and 24 out of 32 disease features; (ii) demonstrate a mild phenocopy in ~400,000 individuals with common genetic variants in MCT8; (iii) assess therapeutic effectiveness, which did not differ among LoF-categories; (iv) advance structural insights in normal and mutated MCT8 by delineating seven critical functional domains; (v) create a pathogenicity-severity MCT8 variant classifier that accurately predicted pathogenicity (AUC:0.91) and severity (AUC:0.86) for 8151 variants. Our information-dense mapping provides a generalizable approach to advance multiple dimensions of rare genetic disorders.

  PublisherOA PDFDOI

• Composition and Priorities of Multidisciplinary Pediatric Thyroid Programs: A Consensus Statement

  Thyroid · 2025-02-14 · 4 citations

  review

  Background: The incidence of pediatric thyroid cancer has been increasing, and care varies due to socioeconomic disparities or differing practice patterns. Clinical guidelines call for care in multidisciplinary teams to minimize variance and provide protocols. Based on expert opinion, we hope to describe the form and function of such multidisciplinary teams for pediatric thyroid programs. Methods: A modified Delphi method to reach consensus statements over two rounds. Twenty-one experts with varying backgrounds responded to each statement on a 9-point Likert scale. Upon completion of the survey, the panel reviewed and shared the results and comments from participants and modified the statements accordingly. This process was repeated such that statements reached consensus, were deemed no consensus, or had no change in the mean. Results: There was an 88% and 83% completion rate for Rounds 1 and 2, respectively. A consensus was observed that there is a distinct definable model of care for pediatric thyroid patients. No consensus was reached for the age range of patients, but programs should care for children with medullary thyroid cancer, differentiated thyroid cancer, and patients with genetic predisposition syndromes. A comprehensive team includes, but is not limited to, a thyroid surgeon, a pediatric endocrinologist, a high-volume fine-needle aspiration (FNA) proceduralist, an oncologist, a nuclear medicine physician, a pediatric pathologist, a pediatric radiologist, and a nurse coordinator. Necessary support services involve care coordination, access to a multidisciplinary tumor board, ability to perform ultrasound-guided FNA, and access to molecular testing. The panel emphasized cross-institutional collaborative research prioritizing guidelines development, disease-specific outcomes, treatment toxicity, and the molecular landscape of thyroid cancer. Conclusions: These consensus statements can be beneficial in improving multidisciplinary care, by describing which elements of pediatric thyroid programs should be consistent across institutions. Overall, the panel agreed that pediatric thyroid centers should provide integrated care with defined team members, services, resources, and research priorities. This model has the potential to standardize various aspects of clinical care and enhance our ability to study patient outcomes, improve health care delivery, and increase scholarly collaboration.

  PublisherDOI

Frequent coauthors

• Ken Kazahaya

  University of Pennsylvania

  71 shared

• Sogol Mostoufi‐Moab

  Children's Hospital of Philadelphia

  59 shared

• Amber Isaza

  Children's Hospital of Philadelphia

  51 shared

• Gary L. Francis

  The University of Texas Health Science Center at San Antonio

  49 shared

• N. Scott Adzick

  University of Pennsylvania

  49 shared

• Aime T. Franco

  Children's Hospital of Philadelphia

  42 shared

• Lea F. Surrey

  Children's Hospital of Philadelphia

  34 shared

• Zubair Baloch

  Philadelphia University

  33 shared

Education

• Pediatric Endocrinology Fellowship

  Uniformed Services University of the Health Sciences

  2002

• Pediatric Residency

  Madigan Army Medical Center Department of Pediatrics

  1996

• MD

  University at Buffalo School of Medicine and Biomedical Sciences

  1993

• BS, Biochemistry

  Canisius College

  1989