Neurocristopathies: Enigmatic Appearances of Neural Crest Cell-derived Abnormalities.

The neural crest is an important transient structure that develops during embryogenesis in vertebrates. Neural crest cells are multipotent progenitor cells that migrate and develop into a diverse range of cells and tissues throughout the body. Although neural crest cells originate from the ectoderm, they can differentiate into mesodermal-type or endodermal-type cells and tissues. Some of these tissues include the peripheral, autonomic, and enteric nervous systems; chromaffin cells of the adrenal medulla; smooth muscles of the intracranial blood vessels; melanocytes of the skin; cartilage and bones of the face; and parafollicular cells of the thyroid gland. Neurocristopathies are a group of diseases caused by the abnormal generation, migration, or differentiation of neural crest cells. They often involve multiple organ systems in a single person, are often familial, and can be associated with the development of neoplasms. As understanding of the neural crest has advanced, many seemingly disparate diseases, such Treacher Collins syndrome, 22q11.2 deletion syndrome, Hirschsprung disease, neuroblastoma, neurocutaneous melanocytosis, and neurofibromatosis, have come to be recognized as neurocristopathies. Neurocristopathies can be divided into three main categories: dysgenetic malformations, neoplasms, and combined dysgenetic and neoplastic syndromes. In this article, neural crest development, as well as several associated dysgenetic, neoplastic, and combined neurocristopathies, are reviewed. Neurocristopathies often have clinical manifestations in multiple organ systems, and radiologists are positioned to have significant roles in the initial diagnosis of these disorders, evaluation of subclinical associated lesions, creation of treatment plans, and patient follow-up. Online supplemental material is available for this article. ©RSNA, 2019.

Infantile hemangioma: pathogenesis and mechanisms of action of propranolol.

Infantile hemangioma (IH) is the most common benign tumor of childhood, with a prevalence of 4 % to 10 %. It is characterized by a proliferative rapid growth phase, which starts after a few weeks of life, followed by a slow regression phase. In IH cases that are potentially disfiguring or life-threatening (10 % to 15 % of all cases), systemic therapy should be promptly initiated. Data source The present study reviews published scientific articles available in reliable electronic databases. Selected were all studies that evaluated the pathogenesis of IH and the mechanisms of action of propranolol. Conclusions The pathogenesis of IH has not been fully elucidated. Studies show that, in the proliferative phase of IH, there is an imbalance of angiogenic factors and an increase in the levels of vascular endothelial growth factor and matrix metalloproteinases 2 and 9. In the regression phase, the levels of these factors decrease, whereas those of antiangiogenic factors, including tissue inhibitors of matrix metalloproteinases, increase. Since 2008, propranolol has become the drug of choice in the treatment of IH, targeting vascular tone, angiogenesis, and apoptosis. Current insights into the pathogenesis of IH allow for the development of new therapeutic strategies.

Blue Rubber Bleb Nevus Syndrome Diagnosed Prenatally as an Epignathus.

The authors present a clinical report of the giant fetal tumor protruding from the oral cavity diagnosed sonographically at 32 weeks of gestation as an epignathus. After delivery, tumor proved to be a presentation of the blue rubber bleb nevus syndrome. To the best of our knowledge, the literature offers no reports on similar cases.

Infantile hemangiomas exhibit neural crest and pericyte markers.

Infantile hemangiomas (IHs) are the most common benign tumors of infancy and occur with greater than 60% prevalence on the head and neck. Despite their prevalence, little is known about the pathogenesis of this disease. Given the predilection of hemangioma incidence on the face and its nonrandom distribution on embryological fusion plates, we postulated that IHs are derived from pericytes of the neural crest. We performed an analysis on 15 specimens at various stages of the IH progression. Experiments performed included immunohistochemical staining, immunofluorescent staining, quantitative real-time polymerase chain reaction, and flow cytometry. We analyzed a number of cell markers using these methods, including cell markers for the neural crest, pericytes, endothelial cells, stem cells, and the placenta. We observed that neural crest markers such as NG2 and nestin were expressed in the hemangioma samples, in addition tomultiple pericytes markers including δ-like kinase, smooth muscle actin, calponin, and CD90. Stem cell markers such as c-myc, oct4, nanog, and sox2 were also more highly expressed in hemangioma samples compared to controls. Our work demonstrates that hemangiomas express pericyte, neural crest, and stem cell markers suggesting a possible pathogenetic mechanism.

Could pericytic mimicry represent another type of melanoma cell plasticity with embryonic properties?

We hypothesize that the interaction between angiotropic melanoma cells and the abluminal vascular surface can induce or sustain embryonic and/or stem cell migratory properties in these tumor cells. As a result, such angiotropic melanoma cells may migrate along the abluminal vascular surface, demonstrating pericytic mimicry. Through these cellular interactions, melanoma cells may migrate toward secondary sites.

Divided nevus of the eyelid: review of embryology, pathology and treatment.

Divided nevus, which is also known as "kissing nevus," "split ocular nevus" and "panda nevus" is a rare congenital dermatological abnormality that occurs on opposing margins of upper and lower eyelids. There is a paucity of literature on this rare anomaly, with most knowledge from this disease process derived from isolated case reports and series. The purpose of this study is to report a new case of divided nevus of the eyelid and to discuss the unique embryology, pathology, and potential treatment options for this rare entity. A systematic review of literature was performed of the English literature on PubMed and Medline with just under 150 cases reported in the literature. The vast majority of the divided nevi seen in this review were medium sized and of the melanocytic intradermal type. There were no described cases of malignant transformation in any of the documented cases. Numerous methods for reconstruction were described including the entire reconstructive ladder with both one and two staged approaches. In this review, we present basic guidelines to the reconstruction of these complicated defects, although ultimate treatment should be individualized and dependent on surgeon comfort.

Fibroepithelioma of Pinkus is a true basal cell carcinoma developing in association with a newly identified tumour-specific type of epidermal hyperplasia.

BACKGROUND: Fibroepithelioma of Pinkus (FEP) has long been viewed as a subtype of basal cell carcinoma (BCC). Recently, however, the proposal has been made that FEP represents a fenestrated trichoblastoma/trichoepithelioma. One of the main arguments is the presence of Merkel cells in FEP, which typically do not occur in BCC. OBJECTIVES: As the new stem cell marker, PHLDA1 (TDAG51), labels trichoepithelioma but not BCC, our aim was to characterize its staining pattern in FEP. Because adnexal tumours have been viewed as recapitulating embryogenesis, we also examined PHLDA1 immunoreactivity in the skin of human embryos and fetuses. METHODS: We studied immunohistochemically PHLDA1 staining in 31 FEPs, 14 BCCs and 16 trichoepitheliomas and compared this with its staining pattern in embryonic skin and with the distribution of Merkel cells. RESULTS: In FEP, PHLDA1 labels the anastomosing network of thin cellular strands but not the basaloid nubbins. During embryogenesis, PHLDA1 stains the basal cell layer of the epidermis, as long as adnexal structures develop. Immunoreactivity for PHLDA1 correlates positively with the presence of Merkel cells. CONCLUSIONS: We propose that the thin anastomosing network of PHLDA1-positive cells represents a type of epidermal hyperplasia specific to FEP. The multifocal BCCs that are PHLDA1-negative develop from this network which becomes incorporated into the tumour. Viewing the anastomosing network as a tumour-specific form of epidermal hyperplasia explains the hitherto enigmatic presence of Merkel cells in FEP.

Patterns in naevoid skin disease: development, disease and modelling.

The aetiology of pattern-formation in human naevoid skin disease remains unknown. However, it is likely that the majority of previously proposed mechanisms - those that simply rely on passive clonal trafficking in embryogenesis - are incomplete. A more comprehensive explanation for pattern-formation in naevi invokes the principle of self-organization. We define two types of patterning: anatomical and functional. Anatomical patterning is where the abnormal clone is limited to regions of pathologic skin, while functional patterning is where the abnormal clone and pathologic skin are spatially uncorrelated. From a theoretical perspective self-organized naevoid patterns may be either secondary to local interactions between normal and aberrant genotypes or due to the interaction between aberrant genotypes and the presence of normal embryonic patterning cues. The latter possibility suggests the critical observation and analysis of patterns in naevoid skin disease may lead to unique insights into key aspects of early human embryogenesis.

p75 Neurotrophin receptor differentiates between morphoeic basal cell carcinoma and desmoplastic trichoepithelioma: insights into the histogenesis of adnexal tumours based on embryology and hair follicle biology.

BACKGROUND: Tumour development is frequently described in the basic pathology literature as a recapitulation of embryogenesis. However, a link between the embryology of the skin and the histogenesis of adnexal tumours has been largely overlooked. The low-affinity p75 neurotrophin receptor (p75NTR) has a profound role in hair follicle biology. We therefore speculated that it is involved in the histogenesis of follicular adnexal tumours. One of the most challenging diagnoses in dermatopathology is differentiating morphoeic basal cell carcinoma from desmoplastic trichoepithelioma. OBJECTIVES: To describe the expression pattern of p75NTR during cutaneous embryogenesis, in the adult hair follicle and in morphoeic basal cell carcinoma and desmoplastic trichoepithelioma. METHODS: Evaluation of the staining pattern for p75NTR was performed using standard immunohistochemical techniques. For comparison, we examined staining for cytokeratin 20 which highlights Merkel cells. RESULTS: All 17 desmoplastic trichoepitheliomas were immunoreactive with > 80% of the cells stained, whereas 12 of the 14 (86%) morphoeic basal cell carcinomas were p75NTR negative. In the two positive cases of morphoeic basal cell carcinoma < 30% of cells were labelled. In the late bulbous hair peg stage and in the postnatal anagen hair follicle p75NTR highlights the outer root sheath. CONCLUSIONS: Our results support the classification of desmoplastic trichoepithelioma as a follicular hamartoma mimicking the outer root sheath. In contrast, the lack of p75NTR expression in morphoeic basal cell carcinoma favours a concept of this tumour as a more primitive follicular lesion with the characteristics of a carcinoma and not a hamartoma. We suggest including p75NTR as a tool in the differential diagnosis between morphoeic basal cell carcinoma and desmoplastic trichoepithelioma.

Giant congenital melanocytic nevi.

BACKGROUND: : Giant congenital melanocytic nevi are rare lesions with the potential to regress into malignant melanoma and/or neurocutaneous melanosis. Appropriate investigations include a screening magnetic resonance imaging scan, neurologic evaluation, and serial clinical observations looking for the development of these complications. Numerous excisional and nonexcisional options have been described for the management of giant congenital melanocytic nevi. METHODS: : A MEDLINE search was performed to obtain all relevant citations. CONCLUSIONS: : To successfully treat these complex lesions, the plastic surgeon must understand the disease process, the natural history and complications, and the options for treatment.

Critical role of IkappaB kinase alpha in embryonic skin development and skin carcinogenesis.

IkappaB kinase alpha (IKKalpha), IKKbeta, and IKKgamma/NEMO form the IKK complex, which is essential for NF-kappaB activation. However, genetic studies have shown that the role of IKKalpha is distinct from that of IKKbeta or IKKgamma in the development of the mouse embryonic skin. Loss of IKKalpha has been shown to cause epidermal hyperplasia, prevent keratinocyte terminal differentiation, and impair the formation of the skin, resulting in the deaths of IKKalpha-deficient (Ikkalpha-/-) mice soon after birth. Recent experimental data from several laboratories have revealed that IKKalpha functions as a tumor suppressor in human squamous cell carcinomas (SCCs) of skin, lungs, and head and neck. Chemical carcinogenesis studies using mice have shown that reduction in IKKalpha expression increases the number and size of Ras-initiated skin tumors and promotes their progression, indicating that reduced IKKalpha expression provides a selective growth advantage that cooperates with Ras activity to promote skin carcinogenesis. In this review, we will summarize these findings from our and other studies on the role that IKKalpha plays in development of the mouse embryonic skin and skin carcinogenesis.

Placental anomalies in children with infantile hemangioma.

Evaluation of the placenta provides some important insights into pathophysiologic changes that take place during the prenatal and intrapartum process. We investigated the pathogenic significance of placental features and their relationship to the development of infantile hemangioma in order to obtain a better understanding of its cause. Placental specimens were reviewed from 26 singleton pregnancies of women whose offspring weighed less than 1500 g. A group of 13 neonates who developed infantile hemangioma in the immediate neonate period were compared with 13 healthy preterm infants of comparable postconception age who had no infantile hemangioma. Pathologic placental changes were analyzed in both groups. Gross lesions with disturbance of the utero-placental circulation were found in all placentas from children who developed infantile hemangioma, including massive retroplacental hematoma in two infants, extensive ischemic infarction in seven, and large dilatated vascular communications, severe vasculitis, chorioamnionitis and funiculitis in four. Placental features included percentages greater than 25% of avascular villi, platelet and fibrin aggregates, and multifocal disease involving more than one histologic section. Examination of 13 placentas of low-birth-weight infants without infantile hemangioma only showed abnormal placentation in one and isolated villous dismaturity in two. The higher ratio of placental pathologic findings in patients with infantile hemangioma suggests that reduced placental oxygen diffusive conductance contributes to fetal hypoxic stress and that hypoxic/ischemic changes in the placenta could be related to infantile hemangioma development via vascular endothelial growth factor and placental growth factor expression, among others, within the villious vessels and throphoblasts.

Correlation of embryonic fusion planes with the anatomical distribution of basal cell carcinoma.

BACKGROUND: The clinical relevance of the anatomic distribution of basal cell carcinoma is not completely understood. Embryonic fusion planes--the regions of mesenchymal migration and fusion of the five primordial facial processes during the 5th to 10th weeks of human development--have been implicated in the pathogenesis of basal cell carcinoma. OBJECTIVE: This study sought to examine the predilection of midfacial basal cell carcinoma for cutaneous anatomical sites correlated to embryonic fusion planes. METHODS AND MATERIALS: Using archived digital images and a detailed anatomic diagram, cases of basal cell carcinoma were coded according to their specific location and were aggregated into two anatomic domains according to their correlation to embryonic fusion planes. The relative tumor densities were calculated. RESULTS: Of the 1,457 cases examined, 859 were located in the midface. Thirty-five percent of the midfacial lesions were located on the domain correlated to embryonic fusion planes, which represented 11.3% of the total surface area of the midface. The relative tumor density of lesions in the fusion plane domain was 3.06 compared to 0.74 for the remaining lesions (p< .001). CONCLUSIONS: Although there is no consensus about the importance of anatomic location in the pathogenesis of basal cell carcinoma, these data indicate that, after adjusting for surface area, basal cell carcinoma was more than four times more likely to occur on an embryonic fusion plane than on other regions of the midface. These data support the possibility of an embryologic role for the pathogenesis of basal cell carcinoma.

[Becker's nevus associated with epidermal nevus: another example of twin spotting?]. / Nevo de Becker asociado a nevo epidérmico: 'un ejemplo más de "manchas gemelas"?

Linear epidermal nevi are believed to be caused by an autosomal dominant lethal mutation that can only be expressed by mosaicism. Becker's nevus can be explained by paradominant inheritance which is only manifested clinically by an acquired loss of heterozygosity. We present the case of a 16-year-old female with an epidermal nevus located on the left side of the neck, and also a Becker's nevus located on the ipsilateral shoulder. It is interesting to speculate that this supposed double mosaicism could be another example of "twin spotting" or non-allelic didymosis, although the possibility that this is a chance association cannot be ruled out, as the lesions are not closely associated.

[Familial occurrence of a type 2 segmental manifestation of cutaneous leiomyomatosis]. / Familiäres Auftreten einer segmentalen Typ-2-Manifestation der kutanen Leiomyomatose.

BACKGROUND: There are several malignant or benign skin diseases which can be explained by the phenomenon of mosaicism or segmental manifestation, e. g. segmental neurofibromatosis 1 or cutaneous leiomyomatosis. Loss of heterozygosity is a crucial element for segmental manifestations. Two types of segmental manifestations can be defined in autosomal dominant skin diseases such as cutaneous leiomyomatosis. Type 1 is caused by a novel postzygotic segmental mutation; type 2 reflects an additional postzygotic loss of heterozygosity of the gene locus responsible for cutaneous leiomyomatosis in a initially heterozygous embryo. Loss of heterozygosity is a genetic process when a heterozygous cell becomes homozygous or hemizygous by loosing the corresponding wild-type allele. This phenomenon can be regarded as a precondition for tumor growth. In type-2 cases, the segmental manifestation is more distinctive with additional disseminated disease because of a germline mutation with heterozygosity of all somatic cells outside the strongly affected area. PATIENTS AND METHODS: A 74-year-old female patient and her 52-year-old son presented with segmental leiomyomas following the lines of Blaschko as well as disseminated skin tumors. The woman has undergone hysterectomy at the age of 29 because of multiple uterine leiomyomas, as had her mother and grandmother. RESULTS: Based on their typical clinical appearance, these cases represent the rare familial occurrence of type-2 manifestation of leiomyomas which indicates a postzygotic loss of the wild-type allele. CONCLUSION: Very unusual is the familial occurrence in mother and son of this type-2 manifestation of cutaneous leiomyomatosis. Apparently the gene locus is prone to a postzygotic loss of heterozygosity.