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.

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.

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.

[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.

Abnormal nevoblast migration mimicking neurofibromatosis.

A patient appeared to have von Recklinghausen type I neurofibromatosis, but her numerous cutaneous tumors were intradermal nevi and not neurofibromas. The patient had hundreds of 1- to 3-cm firm, flesh-colored, dome-shaped papules and pedunculated nodules on her buccal mucosa, eyelids, face, extremities, and trunk as well as a large, confluent, cerebriform tumor extending from the 12th thoracic vertebra to the sacrum. No cafe au lait macules, freckles, or Lisch nodules were present. Several hundred lesions were removed using the carbon dioxide laser. Histopathologic examination of all of the lesions revealed all of them to be intradermal nevi. Our patient's skin disease was clinically very similar to neurofibromatosis. We suggest our patient represents a distinct clinical entity that is related to environmental factors or a mutation that affected nevoblasts or melanoblasts and their derivatives during early embryo development.

[Divided nevus--an embryological experiment of nature]. / Der geteilte Nävus--ein embryologisches Experiment der Natur.

A "divided naevus" (or "kissing naevus") is defined as a congenital melanocytic naevus that occurs on adjacent parts of the upper and lower eyelid and may give the appearance of a single lesion when the eye is closed. We report on four cases of this rare naevus. Two of these were examined histologically and showed the features of compound naevi. The unique occurrence in nature of the divided naevus allows conclusions on the site and time of origin not only of the divided naevus, but possibly also of other congenital melanocytic naevi. The divided naevus must originate at the latest during the period of lid fusion, between the 9th and 20th week of gestation. The fact that the fusion involves only epithelial tissue suggests an epithelial origin of congenital melanocytic naevi, which may later develop secondarily into compound or intradermal naevi by way of "dropping-off".

A case of solitary mastocytoma suggesting a divided form of mast cell nevus.

The case of a 10-week-old boy with a solitary mastocytoma is reported. The lesion, noticed at birth, was located in an area extending from the dorsum of the left hand to the proximal phalanx of the ring and little fingers. It appeared as a coin-sized, flattened dome-shaped, round tumor with occasional blistering. The web between the two fingers was free of cutaneous changes. The diagnosis was confirmed by the histological characteristics: a densely mastocytic infiltration into the dermis. The present case of solitary mastocytoma, referred to as "mast cell nevus", is unique because of its previously undescribed divided form.

Giant pigmented tumour of the scalp--a diffuse neurofibroma or a congenital naevus showing neurofibromatous changes? Immunohistochemical and electron microscopic studies.

A case of giant pigmented tumour of the scalp which developed in a 47-year-old woman is reported. Macroscopically, the tumour showed a peculiar two-layered structure, consisting of an upper non-pigmented and a lower pigmented portion. Histologically, it was composed of elongated neurofibromatous tumour cells with abundant collagen fibres in the non-pigmented portion and round naevus-like cells with abundant melanin pigment in the pigmented portion. S-100 protein and neurone-specific enolase were demonstrated in most of the tumour cells, but neurofilament and myelin basic protein were not detected. Electron microscopy revealed melanosomes in the tumour cells of the pigmented portion. These findings might support a melanocytic origin for the tumour, but the lack of superficial pigmentation and the associated hair loss were against this. The tumour may represent an example of duality of neural crest differentiation.

Clinical and histologic features of nevi with emphasis on treatment approaches.

A nevus is a cutaneous lesion characterized histologically by clustering and disorganization of a variety of cell types in the skin including the epidermis, appendages, melanocytes, and their precursor cells. Commonly, a nevus is congenital but it may be acquired. Owing to the prevalence and variations of melanocytic nevi and their association with malignancy, this article discusses the development, classification, histology, and clinical characteristics of nevi with an emphasis on the relationship to malignancy. Recommendations are provided for treatment of these benign lesions.

Association of epibulbar choristomas with linear cutaneous nevi. Review of the literature.

The authors describe the association of epibulbar choristomas with linear cutaneous nevi of the epidermal and sebaceous variety in 24 cases reported in the literature. The choristomas are of the bilateral, extensive, multiple and complex type. The associated ocular and systemic findings include lid and uveal coloboma, lid choristoma, alopecia, convulsions and growth retardation.

Anatomy and embryology of the eyelids: a review with special reference to the development of divided nevi.

In this review of the basic anatomy and embryology of the human eyelids, the sequence of eyelid differentiation is discussed. The development is important in exploring the formation of divided or "kissing" nevi of the lids. Since the lids are fused from the ninth week until the twentieth week of gestation, one may propose that the precursor elements of the nevus develop during that specific time. Because the epithelium only is fused, melanocytes derived from the neural crest must begin their differentiation in the region of the fused epithelium.

[Phacomatoses. Pathogenesis - Classification - Vascular aspects]. / Les phacomatoses. Pathogénie - Classification - Aspects vasculaires.

The pathogenesis of the phacomatoses, developmental diseases of the embryonic plates, permits an understanding of the different manifestations which characterize these disorders. This pathogenesis also constitutes the best basis for a rational classification. The author sets out the main features of this pathogenesis and its practical applications, and then considers the principal vascular aspects of the phacomatoses, especially in Osler-Rendu disease, Blue Rubber Bleb Naevi, Mafussi's syndrome, the haemangioblastomatoses, Bailey's glomangiomatosis, the Louis-Bar syndrome, Struge-Weber angiomatosis, the syndrome of Bonnet-Dechaume and Blanc, Cobb's syndrome, the angio-osteo-hypertrophic syndromes, von Recklinghausen's neurofibromatosis, Bourneville's tuberous sclerosis, and the melanic phacomatoses.