Miguel Reyes-Mugica

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• M.D.
• Director of Pediatric and Perinatal Pathology at University of Miami

Aims Rhabdomyosarcoma (RMS) is rare, but it is the most common sarcoma in childhood. The World Health Organisation classifies RMS into four main categories, sharing the same terminology of RMS, but the subtypes have different morphology, clinical behaviour and underlying molecular characterisation. Although the main diagnostic categories have remai...

Acute T-cell-mediated transplant rejection, the earliest contributor to immunological graft failure responds variably to T-cell suppression. Early rejection can co-exist with donor-specific antibodies which also shorten graft survival, without affecting graft histology visibly. Here, during early liver transplant rejection, blood leukocytes manifes...

Germline genetic alterations and their associated cancer predisposition syndromes (CPS) are an important cause of pediatric cancer. Early recognition is of great importance for targeted surveillance, early detection, and prompt (personalized) therapeutic interventions. This review provides an overview of non-central nervous system solid pediatric t...

Pediatric germ cell tumors represent a rare but biologically diverse group of neoplasms arising from pluripotent primordial germ cells. The 2022 edition of the WHO Classification of Pediatric Tumors introduced the first organ independent classification of germ cell tumors, reflecting advances in molecular biology, histopathology, and clinical pract...

Most pediatric specialists, including hematologists/oncologists, surgeons, radiologists, and pathologists, are familiar with the diagnosis and management of Wilms tumor (WT). However, it may be challenging to identify the underlying conditions causing cancer predisposition, which can change the management for the patient and potentially their entir...

Aims Kürsteiner canals (KC) were described at least 125 years ago as pharyngeal pouch embryological remnants of parathyroid and thymic development. While considered precursors for a subset of parathyroid cysts and salivary heterotopias (SH), they remain enigmatic. We now define a comprehensive phenotype of KC remnants and investigate their role in...

Introduction. Sarcina organisms are rare, gram-positive, sugar-fermenting cocci, identifiable in tissues only by histologic examination or molecular testing. Since its discovery, the pathogenicity and relevance of Sarcina in the human gastrointestinal tract has remained ill-defined. A recent literature review of 66 reported examples demonstrated th...

Close relationship between melanocytes and neural cells is accepted to reflect their common derivation from the neural crest and tumors combining both elements. We present a series of 10 patients with giant congenital melanocytic nevi (CMN) in which a secondary proliferation (11 lesions) with schwannian and/or perineuriomatous differentiation devel...

Respiratory viral infections remain a leading cause of morbidity and mortality. Using a murine model of human metapneumovirus (HMPV), we identified recruitment of a C1q-expressing inflammatory monocyte population concomitant with viral clearance by adaptive immune cells. Genetic ablation of C1q led to reduced CD8+ T cell function. Production of C1q...

Background Multiple, large or giant congenital melanocytic nevi (CMN) are uncommon and affected patients can show progressive growth and thickening, associate neurocutaneous melanocytosis or develop melanoma. Current treatment modalities are mostly complex surgeries that frequently do not solve the disease and its risks completely. Thus, investigat...

Neuroblastoma accounts for 15% of pediatric cancer deaths, despite multimodal therapy including surgical resection. Current neuroblastoma rodent models are insufficient for studying the impact of surgery and combination treatments, largely due to the small size of mouse models. Human neuroblastoma SK-N-BE(2) cells were injected into the left adrena...

Background: Biliary atresia (BA) is poorly understood and requires liver transplantation (LT) in most children with lifelong risks of immunosuppression. Aims & methods: To determine its genetic basis, we performed GWAS in 811 European BA cases treated with LT in US, Canadian and UK centers, and 4654 genetically matched controls. Whole genome seq...

We describe the first cases of pediatric melanoma with ALK fusion gene arising within giant congenital melanocytic nevi. Two newborn boys presented with large pigmented nodular plaques and numerous smaller satellite nevi. Additional expansile nodules developed within both nevi and invasive melanomas were diagnosed before 10 months of age in both bo...

Respiratory viral infections remain a leading cause of morbidity and mortality. Using a murine model of human metapneumovirus (HMPV), we identified recruitment of a C1q-producing inflammatory monocyte population concomitant with viral clearance by adaptive immune cells. Genetic ablation of C1q led to reduced CD8+ T cell function. Production of C1q...

Background/aims: Medication non-adherence is a leading cause of transplant rejection, organ loss, and death; yet no rigorous controlled study to date has shown compelling clinical benefits from an adherence-improving intervention. Non-adherent patients are less likely to participate in trials, and therefore, most studies enroll a majority of adher...

Mesotheliomas are rare and aggressive tumors that originate from mesothelial cells. Although exceedingly rare, these tumors may occur in children. Different from adult mesotheliomas, however, environmental exposures particularly to asbestos do not appear to play a major role in mesotheliomas in children, in whom specific genetic rearrangements driv...

Duchenne muscular dystrophy (DMD) is characterized by progressive systemic muscle wasting, leading to respiratory paralysis and early death. This X-linked disease is caused by DMD mutations, encoding dystrophin. 1 There is little information regarding gastrointestinal abnormalities in patients with DMD. However, since the esophageal wall includes s...

Mutations in cardiac genes are one of the primary causes of infantile cardiomyopathy. In this study, we report the genetic findings of two siblings carrying variations in the MYBPC3 and SMYD1 genes. The first patient is a female proband exhibiting hypertrophic cardiomyopathy (HCM) and biventricular heart failure carrying a truncating homozygous MYB...

Introduction: Alpha 1 antitrypsin deficiency (A1ATD) accounts for 21% of all pediatric liver transplants due to metabolic disease in the western world. Donor heterozygosity has been evaluated in adults but not to a recipient with A1ATD. Methods: The data of patient were retrospectively analyzed and a literature review performed. Results: We pr...

In the pediatric population, BCL6-correpresor gene (BCOR)–upregulated tumors include primitive myxoid mesenchymal tumors/undifferentiated sarcomas (PMMTI/UND), clear cell sarcomas of the kidney (CCSK), and high-grade neuroepithelial tumors (HG-NET). We investigated DNA methylation (DNAm) and copy number variation (CNV) profiling in these tumors (N...

17q12 deletion syndrome causes developmental abnormalities of the kidneys, pancreas, genital tract, and neurodevelopment, and it has a wide range of phenotypes ranging from fetal demise to normal adulthood with minimal renal impairment. Here we describe a rare case of 17q12 deletion diagnosed prenatally, complicated by anhydramnios and Potter seque...

Autoimmune Disease, Multisystem, with Facial Dysmorphism (ADMFD) is an autosomal recessive disorder due to pathogenic variants in the ITCH gene. It is characterized by failure to thrive, dysmorphic facial features, developmental delay, and systemic autoimmunity that can manifest variably with autoimmune hepatitis, thyroiditis, and enteropathy, amon...

Background: Operational tolerance after retransplantation of the intestine has never been reported. Purpose: To two recently described intestine transplant recipients with operational tolerance, we now add a third. Methods: Review of case record and immunological testing to confirm donor-specific hyporesponsiveness in multiple immune cell comp...

Acute hepatic failure is associated with high morbidity and mortality for which the only definitive therapy is liver transplantation. Some fraction of those who undergo emergency transplantation have been shown to recover native liver function when transplanted with an auxiliary hepatic graft that leaves part of the native liver intact. Thus, trans...

Background Acinic cell carcinoma (AciCC) is the second most common pediatric malignant salivary gland tumor. However, there are limited pathology publications about this tumor in the pediatric population. Methods We describe four pediatric AciCC cases diagnosed between 2000 and 2021 in our institute. Reticulin histochemistry plus immunohistochemis...

Teratocarcinosarcoma is an extremely rare malignancy of the nasal cavity and paranasal sinuses. It exhibits both sarcomatous and carcinomatous components. Less than 100 cases are reported. It presents in adults with only two reported cases in infancy. Here we present a case of 3-week-old female with antenatally detected ocular mass. MRI revealed an...

Introduction Appendicular foreign bodies are a rare, under-described cause of appendicitis. We performed this study to determine the varied causes and consequences of foreign-body appendicitis. Methods On retrospective review of the pathology archives of seven institutions, we identified 56 appendix specimens containing a foreign body (defined as...

Calyceal diverticula (CD) are relatively uncommon urologic conditions that generally follow an asymptomatic course and rarely require medical intervention. CD are thought to have a congenital origin due to abnormalities during the process of ureteral bud formation. Clinically and radiologically, they can mimic multiple neoplastic and non-neoplastic...

A 15-month-old full-term boy of African descent with an asymptomatic sickle cell trait presented with episodes of transient erythematous subcutaneous nodules involving the entire body except the face, since 2 weeks of age. The skin lesions evolved to areas of lipoatrophy and hyperpigmentation. An initial skin biopsy, studied at a different departme...

Idiopathic orbital inflammation is rare in the pediatric population, particularly infants. It can be mistaken either for orbital infection or malignant tumors. We report the case of a 9-month-old previously healthy white boy who presented with right upper eyelid swelling. Magnetic resonance imaging revealed an abnormal T2-hypointense enhancing lesi...

Immunohistochemical procedures are complex, multiparameter assays that must take into account many factors during protocol development. The overall goal of a successful immunohistochemistry protocol is to produce a specific, sensitive, robust, and reproducible stain. Each step in the protocol has an important role in this outcome. This chapter focu...

Background: Rhabdomyomatous mesenchymal hamartomas (RMHs), also termed striated muscle hamartomas, are rare benign tumors of skin and subcutis, which mostly occur at birth with a predilection for the head and neck. Simple surgical excision is the treatment modality of choice with excellent prognosis. Objective: To review the spectrum of the diff...

Pediatric tumors are uncommon, yet are the leading cause of cancer-related death in childhood. Tumor types, molecular characteristics, and pathogenesis are unique, often originating from a single genetic driver event. The specific diagnostic challenges of childhood tumors led to the development of the first World Health Organization (WHO) Classific...

Nemaline Myopathy (NM) is a disorder of skeletal muscles caused by mutations in sarcomere proteins and characterized by accumulation of microscopic rod or thread‐like structures (nemaline bodies) in skeletal muscles. Patients diagnosed with both NM and infantile cardiomyopathy are very rare. A male infant presented, within the first few hours of li...

Disorders of sex development (DSD) are a group of congenital conditions associated with anomalous development of internal and external genital organs. Ovotesticular disorder of sex development (OT-DSD) is a condition in which a child is born with both testicular tissue (that possesses variable fertility potential within seminiferous tubules) and ov...

The lysine methyltransferase SMYD1 was first identified in mice and shown to be important for embryonic cardiac development. Subsequently, we reported the first analysis of SMYD1 in adult myocardium and demonstrated that cardiomyocyte-specific loss of SMYD1 lead to progressive cardiac hypertrophy and heart failure, and showed that this enzyme is ne...

Salivary gland secretory carcinoma (SSC) is a neoplasm with characteristic histologic features, similar to those of secretory carcinoma of the breast. Only a few pediatric SSC cases have been reported, all with ETV6-NTRK3 fusion. We present four new pediatric SSC examples, one with a novel ETV6-RET fusion. Four cases of SSC were diagnosed between 2...

Objective Juvenile localized scleroderma (LS) is an autoimmune disease of the skin whose pathogenesis is not well understood due to the rarity of the disease. This study was undertaken to determine the skin transcriptome in skin biopsy tissue from children with juvenile LS compared to pediatric healthy controls, with identification of significant m...

Background Progressive familial intrahepatic cholestasis type 1 (PFIC1) arises from biallelic variants in the ATP8B1 gene that annul FIC1 activity, resulting in progressive liver disease. Liver transplant (LT) is indicated in refractory disease; however, post-LT complications including worsening diarrhea and steatohepatitis progressing to fibrosis...

In the past decade, there have been major advances in knowledge related to mesenchymal tumors, and new genetic alterations are being delineated. We report a mesenchymal spindle cell neoplasm harboring a novel gene fusion in an infant. Histopathologically, the neoplasm shared some features with sclerosing perineurioma, but immunohistochemically, EMA...

Background Ciliary defects cause heterogenous phenotypes related to mutation burden which lead to impaired development. A previously reported homozygous deletion in the Man1a2 gene causes lethal respiratory failure in newborn pups and decreased lung ciliation compared with wild type (WT) pups. The effects of heterozygous mutation, and the potential...

We have encountered a lesion of the pediatric testis, termed "nodular maturation," that clinically mimics a testicular neoplasm causing ultrasound abnormalities that may lead to surgical excision. To our knowledge, it has only been described anecdotally in textbooks without a series or description in the literature. We, therefore, report 8 cases in...

Familial hemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyperinflammatory syndrome resulting from defective cytotoxicity. A previously healthy 3-month-old female presented with fever, irritability, abdominal distention, and tachypnea. She ultimately met all eight HLH-2004 diagnostic criteria, accompanied by elevated CXCL9. Initial e...

Background Patients with Tetralogy of Fallot with pulmonary stenosis (ToF/PS), the most common form of cyanotic congenital heart disease (CHD), develop adverse right ventricular (RV) remodeling, leading to late heart failure and arrhythmia. We recently demonstrated that overactive β-adrenergic receptor signaling inhibits cardiomyocyte division in T...

Linear Sebaceous Nevus Syndrome is a rare disorder that presents with nevus sebaceus in association with corneal dermoids, colobomas, choroidal osteomas, and arachnoid cysts. It is thought to represent a mosaic RASopathy. These are disorders characterized by postzygotic somatic mutation in genes involved in RAS/MAPK signaling pathway. In this repor...

Objectives Very-long-chain acyl-CoA dehydrogenase deficiency (VLCADD) is a disorder of fatty acid oxidation. Symptoms are managed by dietary supplementation with medium-chain fatty acids that bypass the metabolic block. However, patients remain vulnerable to hospitalisations because of rhabdomyolysis, suggesting pathologic processes other than ener...

Background Mesenchymal chondrosarcoma is a rare and aggressive bone tumor with few reports of primary tumor in the chest wall. Case We report a case of a 17-year-old male presenting with back pain and a posterior mediastinal mass. Imaging demonstrated what was thought to be a benign chondral tumor. The patient underwent resection which confirmed e...

Large/giant congenital nevi (L/GCMN) are benign neoplasms of the melanocytic neural crest lineage covering extensive areas of skin presenting risk for melanoma. Surgical resection often leads to scarring and trauma. Histone deacetylase inhibitors (iHDACs) as topical therapeutic agents may prove beneficial as an alternative/adjunct to surgery in thi...

Myoepithelial tumors of soft tissue are rare mesenchymal neoplasms that overlap with their salivary gland and skin counterparts at both the histopathologic and molecular levels. EWSR1 gene rearrangements with various fusion partners represent a common genetic event in myoepithelial tumors of soft tissue, whether benign or malignant, and may prove u...

A "central pathology" or "site" reading of biopsy slides is used in liver transplant clinical trials to determine rejection. We evaluated inter-rater reliability of readings of "rejection or not" using digitized slides from the Medication Adherence in Pediatric Liver Transplant Recipients (MALT) study. 4 masked experienced pathologists read the dig...

Introduction Somatic internal tandem duplication of 3’ of BCOR ( BCOR ITD) has been found in clear cell sarcomas of the kidney (CCSK), soft tissue undifferentiated round cell sarcomas/primitive myxoid mesenchymal tumors of infancy (URCS/PMMTI), and a subgroup of central nervous system high-grade neuroepithelial tumors (CNS-HGNET). BCOR ITD+ tumors...

Cystic partially differentiated nephroblastoma (CPDN) and cystic nephroblastoma are paediatric renal tumours characterised by the presence of a variable combination of primitive epithelium, immature stroma and blastema. Cystic nephroblastoma can be identified by the presence of solid expansile areas of tumour which are absent in CPDN. The distincti...

In inflammatory dermatoses, dermal melanophages (MLP) are ascribed to “pigment incontinence”, with melanin “dropping down” from the epidermis. Although this is analogous to the “dropping down” of melanocytic nevus cells (Abtropfung); MLP in ordinary nevi have not been systematically studied ‐ so “pigment incontinence” may not apply to MLP in nevi....

The cover image is based on the Original Article CD154‐expressing CMV‐specific T cells associate with freedom from DNAemia and may be protective in seronegative recipients after liver or intestine transplantation by Chethan Ashokkumar et al., https://doi.org/10.1111/petr.13601.

Factors regulating transcription of pluripotency genes in congenital nevo-melanocytes are not known. Nevo-melanocytes belong somewhere in-between the ends of a spectrum where the normal epidermal melanocyte represents one end and a melanoma cell with multiple genetic abnormalities represents the other. Cells from large/giant congenital nevi (L/GCMN...

Reticular dysgenesis is an autosomal recessive form of severe combined immunodeficiency (SCID) that usually manifests in newborns. It is a unique example of an immune deficiency that is linked to dysfunctional mitochondrial energy metabolism and caused by adenylate kinase 2 (AK2) deficiency. It is characterized by an early differentiation arrest in...

One million patients with congenital heart disease (CHD) live in the United States. They have a lifelong risk of developing heart failure. Current concepts do not sufficiently address mechanisms of heart failure development specifically for these patients. Here, analysis of heart tissue from an infant with tetralogy of Fallot with pulmonary stenosi...

Cell‐mediated immunity to CMV, if known, could improve antiviral drug therapy in at‐risk children and young adults with LT and IT. Host immunity has been measured with CMV‐specific T cells, which express IFNγ, but not those which express CD154, a possible substitute for IFNγ. CMV‐specific CD154+ T cells and their subsets were measured with flow cyt...

Cystic partially differentiated nephroblastoma (CPDN) and cystic nephroblastoma are paediatric renal tumours characterised by the presence of a variable combination of primitive epithelium, immature stroma and blastema. Cystic nephroblastoma can be identified by the presence of solid expansile areas of tumour which are absent in CPDN. The distincti...

Background/purpose: Synoptic, or standardized, reporting of surgery and pathology reports has been widely adopted in surgical oncology. Patients with Hirschsprung disease may experience morbidity related to surgical factors or underlying pathology and often undergo multiple operations. Our aim is to improve the postoperative outcome and care of pa...

45,X/46,XY mosaicism is one of a heterogenous group of congenital conditions known as differences (disorders) of sex development (DSD) that results in abnormal development of internal and external genitalia. Patients with DSD, particularly those with segments of the Y chromosome, are at increased risk for germ cell tumors including gonadoblastoma....

Renal mass lesions with a follicular architecture resembling atrophic kidney have been described, but their distinction from thyroid-like follicular carcinoma of the kidney remains controversial. We collected 8 cases of this purported "atrophic kidney"-like lesion to fully describe their clinical and histologic spectrum, their possible etiology, an...

Context: - Intestinal neuronal dysplasia type B (IND B) is a controversial histopathologic phenotype that has been associated with intestinal dysmotility, either as an isolated condition or in conjunction with established pathologic disorders (eg, Hirschsprung disease). Many factors contribute to the debate over the existence and/or clinical signi...

Background: Omipalisib has been found to affect the viability of cancer cells. However, its effect on clonogenicity - a feature of cancer stem cells, is not clear. Cells isolated from neurocutaneous melanocytosis (NCM) patients' lesions grow clonogenically. The aim of this study was to investigate the effect of omipalisib treatment on clonogenic g...

SOX8 is an HMG-box transcription factor closely related to SRY and SOX9. Deletion of the gene encoding Sox8 in mice causes reproductive dysfunction but the role of SOX8 in humans is unknown. Here, we show that SOX8 is expressed in the somatic cells of the early developing gonad in the human and influences human sex determination. We identified two...

SOX8 is an HMG-box transcription factor closely related to SRY and SOX9. Deletion of the gene encoding Sox8 in mice causes reproductive dysfunction but the role of SOX8 in humans is unknown. Here, we show that SOX8 is expressed in the somatic cells of the early developing gonad in the human and influences human sex-determination. We identified two...

Capillary hemangioma is a rare benign lesion in the testicle, particularly in pediatrics. It can mimic malignancy, leading to radical orchiectomy. We present a case of a testicular hemangioma in a child, and review the literature on testicular hemangiomas in this age group. A hypervascular testicular lesion without elevated tumor markers may warran...

Fibrosis is commonly described in heart allografts lost late after transplantation. CMR-derived ECV is a validated measure of DMF in native adult hearts that may predict heart failure and mortality. We explored associations of ECV with histologic myocardial fibrosis and clinical features after pediatric heart transplantation. Twenty-five recipients...

Background: The XX male disorder of sex development (DSD) is a rare condition that is most commonly associated with the presence of the SRY gene on one of the X chromosomes due to unequal crossing-over between sex chromosomes during spermatogenesis. However, in about 20% of the XX male individuals, SRY is missing, although these persons have at le...

Linked Article: Kinsler et al. Br J Dermatol 2017; 176:1131–1143.

Germ cell tumors in the pediatric age group conform a heterogeneous collection of neoplastic entities whose common denominator is their origin in progenitor germ cells. The three major types include teratoma, embryonal carcinoma/yolk sac tumor, and seminoma/dysgerminoma. Their common extragonadal locations are consistent with migratory pathways of...

Nonadherence to immunosuppressant medications is a leading cause of poor long-term outcomes in transplant recipients. The Medication Level Variability Index (MLVI) provides a vehicle for transplant outcome risk-stratification through continuous assessment of adherence. The MALT (Medication Adherence in children who had a Liver Transplant) prospecti...

Cystinosis is the most common cause of inherited renal Fanconi syndrome in young children, and typically presents with laboratory findings of a proximal tubulopathy and corneal crystals by one year of age. We describe here renal biopsy findings in a 20-month-old patient with an atypical presentation of distal renal tubular acidosis, diabetes insipi...

The Native American Pima population has the highest incidence of insulin resistance (IR) and type 2 diabetes mellitus (T2DM) of any reported population, but the pathophysiologic mechanism is unknown. Genetic studies in Pima Indians have linked acyl-CoA dehydrogenase 10 (ACAD10) gene polymorphisms, among others, to this predisposition. The gene code...