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We present a case of squamous cell carcinoma arising in a naevus sebaceous of Jadassohn (NSJ) in a 15-year-old girl. Both these events are rare, and this is the first reported case of a squamous cell carcinoma developing in NSJ in a child. The previous literature on sebaceous naevi and malignancies arising thereof is reviewed and discussed. Early excision is recommended in any cases of nodular change in sebaceous naevi in all age groups.
A 15-year-old girl presented to clinic complaining of an enlarging warty lesion on the back of her scalp. She had always had a large hairless birthmark in that area, but during puberty it had grown and become thicker. She often traumatised the lesion when brushing her hair.
On examination, she had a 6 cm×3 cm pale-yellow warty friable lesion on the left parietal part of her scalp. Within this lesion there were multiple small (1–2 mm in diameter) darkly pigmented firm nodules and one central reddened papular lesion 4 mm in diameter (Fig. 1) . The appearance was that of a sebaceous naevus. There was no local or regional lymphadenopathy.
Figure 1(A) Appearance of the lesion at presentation. (B) Closer view of the lesion, with scale.
A staged (two-part) excision was performed, as the lesion was too large for complete excision and primary closure. The first excision included the red papular central nodule. The second excision was performed 4 weeks later (Fig. 2) . This was somewhat earlier than intended owing to the unexpected histological finding of squamous cell carcinoma in the first specimen. Histology of the residual lesion did not show any malignant changes.
Figure 2Preoperative view, prior to the second stage of excision.
Section 1. The skin showed hyperkeratosis with papillomatosis and irregular acanthosis. The superficial dermis contained a severe chronic inflammatory cell infiltrate. Hair follicles were scanty, and apocrine glands were not seen. Small foci of dysplastic squamous epithelium were identified, and in one area this infiltrated the superficial dermis.
The features were most in keeping with a sebaceous naevus showing a focus of completely excised superficially invasive squamous cell carcinoma.
Section 2 (4 weeks later). This showed that the remaining sebaceous naevus had been completely excised, and there were no further areas of squamous cell dysplasia.
2. Discussion
A sebaceous naevus or naevus sebaceous of Jadassohn (NSJ) is a hamartoma of both epithelial and non-epithelial skin components that undergoes age-related change.
It was first described by Jadassohn in 1895, and histologically it is a complex lesion consisting of abnormalities of hair follicles, sebaceous glands, epidermis and sweat glands in varying proportions. It is an uncommon lesion, occurring in 0.3% of neonates.
particularly the scalp, and presents as a yellowish plaque or mammillated patch of alopecia. In 1965, Mehregan and Pinkus described the three-stage life history of NSJ:
Two-thirds of cases are present at birth; the rest develop in early childhood. The early infantile stage is characterised by papillomatous epithelial hyperplasia and underdevelopment of hairs.
2.
During puberty there is a massive overdevelopment of sebaceous glands, with epidermal hyperplasia and maturation of apocrine glands.
3.
In 10–20% of cases a third stage, usually occurring in the fourth to seventh decades, involves the development of a large variety of benign and malignant neoplasms of epidermal, adnexal and mesenchymal origin.
Rarely, very extensive NSJ (those over 10 cm in diameter and linear), especially those affecting the face, are associated with cerebral malformations and pathological changes of the brain similar to those seen in tuberousy sclerosis and neurofibromatosis. This can result in epilepsy and mental retardation, and is known as the sebaceous naevus syndrome.
the spectrum of benign tumours included syringocystadenoma papilliferum (the most common), syringoma, apocrine cystadenoma, hidradenoma, sebaceous epithelioma and tricholemmal proliferations.
Of the malignancies that are associated with NSJ, basal cell carcinoma is the most common;
In 1936, Pautrier suggested that malignant lesions developing in NSJ behave in a relatively indolent fashion and are, therefore, easily controlled by simple excision.
Of the 997 cases of NSJ that they examined, 103 were associated with epithelial neoplasms and, of these, nine were malignant (excluding basal cell carcinomas). Of these nine, only one was a squamous cell carcinoma, presenting in a 42-year-old man. This behaved aggressively and had metastasised to local lymph nodes at the time of presentation. The patient died within 11 months of diagnosis. The development of squamous cell carcinoma within an NSJ is a relatively rare event: in the five largest series of NSJ (a total of 2043 cases examined) this was the only reported case.
In conclusion, this case is unusual for two reasons: first, because squamous cell carcinoma is an uncommon malignancy in NSJ; and, second, because of the patient's unusually young age. There are five previously reported cases in the English language literature of malignant lesions developing in a childhood NSJ, all of which were basal cell carcinomas,
and, as far as we are aware, this is the first reported case of a squamous cell carcinoma developing in a NSJ in a child.
The malignant or third stage of this lesion usually occurs in the later decades of affected patients' lives, with a lifetime risk of malignant change of between 5 and 20%.
Cribier et al have argued that the incidence of BCC in NSJ may be much lower (it was only 0.8% in their series of 596 cases) because trichoblastomas (a benign tumour) may have previously been misdiagnosed as BCC.
Accordingly, they advocated a conservative approach to managing NSJ. However, this retrospective study reviewed case notes over a 68-year period and, we feel, does not fulfil the criteria needed to change current practice. We agree with the majority view in the literature, which is to favour excision of NSJ, especially if any nodular or atypical features are present, even in children.
Whereas NSJ was previously dismissed as a benign lesion, albeit of malignant potential in adults, this case emphasises the importance of early excision at all ages, especially if there are any irregular areas within the lesion.
References
Alessi E
Sala F
Nevus sebaceous: a clinicopathologic study of its evolution.
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