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Nevus sebaceous - Organoid nevus

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What is sebaceous nevus?

Nevus sebaceous is a congenital hairless skin hamartoma that typically occurs on the face or scalp.
These benign skin malformations tend to be present at birth and grow commensurate with the growth of the child. These organoid lesions usually occur along the lines of Blaschko in a linear configuration. Initially the surface of the nevus may be smooth and the color may be yellow or yellowish orange. The organoid lesion thickens as the child grows and the skin becomes verrucous during adolescence.

Nevus sebaceous is also known as an "Organoid nevus" and "Nevus sebaceus of Jadassohn". The organoid lesion is an overgrowth of sebaceous glands in the particular area of the skin and hence the names. Josef Jadassohn (1863-1936) described this organoid condition in 1895. These rare lesions, also known as Jadassohn's disease II, may affect males and females of all races equally.

These lesions occur in 1 to 3 of 1000 births. In some cases the lesions may be cosmetically disturbing, requiring their surgical removal.
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It has been reported that up to 10% of patients with sebaceous organoid lesions will go on to develop further symptoms of systemic anomalies. In rare cases they may be involved with speckled lentiginous nevus with systemic anomalies or other syndromes.

Nevus sebaceous pathogenesis

Nevus sebaceous is believed to be caused by postzygotic mosaic mutations in the HRAS or KRAS genes. An abnormality of the PTCH gene has been reported in some cases of organoid lesions. Deletions in the PTCH tumor suppressor gene on chromosome 9p22.3 may be the cause of malignant transformation. There is an increased expression of androgen receptors at the lesion site leading to triggering of overgrowth after puberty.

Generally there are two stages in the development of these organoid overgrowths. The early stage is characterized by papillomatous epithelial hyperplasia. There is exophytical overgrowth of epithelial cells. The hair follicles are small and the oil glands are normal. After puberty, sebaceous and apocrine glands proliferate and become hyperplastic. The hair follicles may regress and disappear. The epidermis becomes verrucous (covered with wart-like projections).

Nevus sebaceous complications

In some patients with extensive organoid lesions, linear nevus sebaceus syndrome may be present with associated with abnormalities of the central nervous system, ophthalmologic changes, skeletal deformities and malignancy. The organoid overgrowths have been observed together with speckled lentiginous lesions which may progress into malignant conditions.

Linear nevus sebaceous syndrome (LNSS)

LNSS is characterized a large organoid lesion with a plethora of systemic abnormalities. It is a typical midline nevus, small in size at birth and enlarged at puberty with verrucous epidermis with possibility of malignancy, especially basal cell epithelioma. Several organ systems are involved in this rare organoid syndrome. The syndrome is believed to be caused by an autosomal dominant lethal mutation that survives by somatic mosaicism (Gorlin et al., 2001).
image of organoid nevus sebaceous of Jadassohn
image of organoid nevus sebaceous of Jadassohn
The patient may affected by several disorders including seizures, intellectual deficit, aortic coarctation (narrowing of the aorta), skeletal dysplasia (dwarfism), retinal anomalies and urogenital anomalies. Early multidisciplinary care is recommended including removal of the organoid nevus followed by orthopedic and ophthalmic care.

Phakomatosis pigmentokeratotica

The organoid sebaceous lesion is sometimes present in association with nevus spilus and is known as phacomatosis pigmentokeratotica. These may be other extracutaneous anomalies associated with the organoid nevus syndrome. Hemiatrophy (one side of the body under-developed), muscle weakness and sensory nerve abnormalities are some of the symptoms associated with phakomatosis pigmentokeratotica.

It is presumed to be caused by twin spotting genetic mechanism, which is a specific form of somatic recombination of two genetically different clones of neighboring cells in a background of normal cells. As there is the possibility of phakomatosis pigmentokeratotica organoid lesions turning malignant, the patient must be closely monitored to ensure early detection and treatment of malignancy.

Nevus sebaceous and malignancy

In rare cases, after puberty, nevus sebaceous of Jadassohn is known to give rise to benign tumors such as trichoblastoma, sebaceoma and syringocystadenoma papilliferum. Malignant neoplasms, including linear squamous cell papilloma and malignancies such as basal cell epithelioma, basal cell carcinoma or sebaceous carcinoma may also develop. Rapid, circumscribed enlargement, ulceration or development of an exophytic nodule should raise suspicion of malignant transformation.

Izumi M. et al. reported on their study of ten cases of sebaceous carcinoma arising in nevus sebaceus. The organoid lesions predominantly occurred on the scalp of elderly women with several pathological features of sebaceous carcinoma. They reported that "all cases were treated by excision of the malignant lesion, with or without inclusion of the nevus sebaceus. In a follow-up period of 1-7 years, there was no case of recurrence".

It is generally assumed that rare malignant conditions in the organoid lesions occur after puberty. However there are nine documented cases of basal cell carcinoma arising in organoid lesions in childhood. Jensen AL. et al. reported a case of an 8-year-old male child with nevus sebaceus and facial trichoepitheliomas who developed a basal cell carcinoma. Altaykan A. et al. reported, "few cases of basal cell carcinoma arising in nevus sebaceous before puberty were reported. Herein, we report a case of basal cell carcinoma arising in a nevus sebaceous on the scalp of a 10-year-old boy".

Treatment and management of organoid lesions

Patients with extensive linear lesions should be appropriately diagnosed and evaluated to rule out malignant conditions and systemic involvement. If the sebaceous lesion is small and not cosmetically disfiguring, it may require only periodic clinical evaluation.

Prophylactic surgical removal may be considered if the organoid growth may give rise to cosmetic problems in the future. In some patients, the surgical removal may not be feasible, considering the extent of the lesion and the areas affected. Other nonsurgical treatment modalities such as carbon dioxide laser therapy and photodynamic therapy (photochemotherapy) along with topical applications have been attempted with varying degrees of success. However these procedures may impede the detection and diagnosis of malignancy in the organoid nevus sebaceous of Jadassohn.
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Reference:
1.http://omim.org/entry/163200
2.Izumi M, Tang X, Chiu CS, Nagai T, Matsubayashi J, Iwaya K, Umemura S, Tsuboi R, Mukai K. Ten cases of sebaceous carcinoma arising in nevus sebaceus. J Dermatol. 2008 Nov;35(11):704-11.
3.Santibanez-Gallerani A, Marshall D, Duarte AM, Melnick SJ, Thaller S. Should nevus sebaceus of Jadassohn in children be excised? A study of 757 cases, and literature review. J Craniofac Surg. 2003 Sep;14(5):658-60.
4.Altaykan A, Ersoy-Evans S, Erkin G, Ozkaya O. Basal cell carcinoma arising in nevus sebaceous during childhood. Pediatr Dermatol. 2008 Nov-Dec;25(6):616-9.
Image source: http://en.wikipedia.org/wiki/File:NaevusSebaceus_res.jpg
Image author: Phrontis
Image licence: cc-by-sa-3.0
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