Malignant Transformation of Facial Nevus Sebaceous – Unrelated with Size

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A 34-year-old male presented with swelling for 6 months and came for cosmetic reasons. He initially noted a skin-coloured swelling from childhood which increased in size over the past 6 months. Examination revealed a solitary 4-mm skin-coloured non-tender papule in the left nasolabial fold with telangiectasias surrounding the lesion, over the nose, chin and bilateral malar prominence [Figure 1]. Dermoscopy showed yellowish globules with central brown globules and surrounding branched and reticular vessels [Figure 2]. An excisional biopsy was done with the differentials of sebaceous hyperplasia and appendageal tumours such as sebaceoma, trichoepithelioma, trichofolliculoma. H&E stain of skin biopsy showed epidermis and dermis with the marked proliferation of sebaceous glands, with many of the sebaceous ducts being superficially located and not associated with hair follicles. Furthermore, a small area of basaloid cell islands with surrounding retraction artefacts was noted in the form of clear spaces in the superficial dermis. These basaloid tumour cell islands showed mild-to-moderate membranous positivity for BerEP4. Epithelial membrane antigen (EMA) immune stain was negative in basaloid tumour cell islands but highlighted sebaceous glands. Melan-A immunostain was negative in basaloid tumour cell islands [Figure 3a-e]. Diagnosis of nevus sebaceous (NS) with basal cell carcinoma (BCC) was given based on histopathology.

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Figure 1:

Clinical image – skin-coloured papule of 4 mm in size in the nasolabial fold with telangiectasias surrounding the lesion.

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Figure 2:

Dermoscopy of the lesion – yellowish globules with central brown globule and surrounding branched and reticular vessels (Dermlite 4).

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Figure 3:

Photomicrographs of skin biopsy. (a) Photomicrograph of skin biopsy showing epidermis and dermis with marked proliferation of sebaceous glands, many of the sebaceous ducts are superficially located and not associated with hair follicles (Haematoxylin and Eosin (H&E) stain, 10×). (b) A small area in the superficial dermis with the presence of basaloid cell islands (black arrow) with surrounding retraction artefacts was noted in the form of clear spaces (red arrow) (H&E stain, 20×). (c) These basaloid tumour cell islands show mild-to-moderate membranous positivity for BerEP4 [Immunohistochemistry (IHC) stain, 20×]. (d) Epithelial membrane antigen (EMA) immunostain is negative in basaloid tumour cell islands but highlights sebaceous glands (IHC stain, 40×). (e) Melan-A immuno-stain is negative in basaloid tumour cell islands (IHC stain, 20×).

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NS also known as nevus sebaceum of Jadassohn is a common congenital hamartoma of the skin. First described in 1895, and its prevalence is <1%. The lesions may be linear, round, oval or irregularly shaped and generally asymptomatic.^[1] 95% of lesions are in the head-and-neck region with scalp lesions associated with alopecia. 23.5% of NS is limited to the face region.^[2] NS progresses in three phases. The first phase is in infancy and childhood characterised by underdevelopment of the hairs and sebaceous glands with quiescent waxy yellow, flat or mammillated plaque. The second phase is characterised by massive development of sebaceous glands, with elevated, verrucous or nodular appearance and histologically as hypertrophic sebaceous glands with papillomatosis and hyperkeratosis of the overlying epidermis. This phase usually begins in puberty. The third stage is in late adult life complicated by the development of benign or malignant tumours from the existing NS.^[3]

NS is known for neoplastic changes (3%); however, no specific correlation is available with age, duration or size of the lesion.^[2] The most frequent tumours arising from NS are trichoblastoma (34.7%), syringocystadenoma papilliferum (24.7%), apocrine adenoma (10%) and trichilemmoma (5.3%). The incidence of BCC in NS is rare and varies from 0.8% to 1.1%.^[4] The pathophysiology of BCC involves the tumour suppressor gene, patched gene (PTCH) and the sonic hedgehog signal transduction pathway. NS has been linked to heterozygosity loss at 9q22.3, the patched locus. NS may proceed to BCC as a result of this molecular genetics.^[5] Very rarely multiple tumours are observed within one pre-existing lesion.

Dermoscopy of NS varies with the evolution of the disease and it includes yellowish/brown globules, yellowish homogenous appearance and linear irregular or arborescent vessels.^[6] Dermoscopic features of BCC are blue–grey ovoid nests, blue–grey globules, maple leaf-like areas, spoke wheel structures, ulceration and arborising vessels.^[7]

Histopathology of NS varies with the clinical stage and it includes immature sebaceous glands localised to the deeper dermis and reticular dermis in patch and verrucous plaque stage, respectively. Matured sebaceous glands are in the epidermis in the nodular stage.^[4] EMA is the immunohistochemistry marker for the sebaceous glands. Key features of BCC histopathology include islands of basaloid tumour in a palisading pattern with retraction clefts between the tumour stroma. BerEP4 is the IHC marker for BCC.

Management of NS remains controversial, and no clear consensus is available. Surgical excision, laser ablation and dermabrasion are the treatment options.^[8] Malignant transformation remains a low risk; however, in our case, the lesion was very small, and without any obvious clinical change in the lesion, progressed to BCC diagnosed only with histopathology, which is rare. Close monitoring of the NS lesion is recommended with prophylactic excision and histopathology confirmation which will yield optimal results.