Advanced Dermoscopic Identification of Non-Melanocytic Skin Lesions

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Dermoscopy serves as a pivotal tool in differentiating pigmented non-melanocytic lesions from both benign and malignant melanocytic ones. It offers distinctive characteristics that facilitate this distinction. Beyond pigmented lesions, dermoscopy has also been instrumental in identifying non-pigmented lesions, providing valuable diagnostic insights, particularly in cases of pruritic rashes.

Vascular Lesion Dermoscopy

Dermoscopy of vascular lesions, such as haemangiomas or angiomas, presents specific features:

Extensive red-blue lacunes

Red-bluish-black homogeneous regions

Reactive haemangiomas or pyogenic granulomas are marked by a distinct keratinised border, often accompanied by vascular structures and white linear 'rail lines'. Differentiating these from amelanotic melanomas can be challenging without a biopsy.

Cutaneous lymphatic malformations, previously known as lymphangiomas, exhibit yellowish lacunes that may appear blood-tinted. In contrast, Kaposi sarcoma, under polarised microscopy, is identified by a multicoloured rainbow pattern alongside bluish-red hues, scaling, and small brown globules.

Dermoscopy of Haemorrhage

Haemorrhage is distinguishable from melanin pigmentation by its purple hue. On plantar surfaces, it may display a parallel ridge pattern with peripheral reddish-black globules. In some cases, shaving the surface keratin or performing a biopsy is necessary to rule out melanoma.

Dermoscopy of Dermatofibroma

Dermatofibromas, also known as histiocytomas, are typically diagnosed through their firm texture and dimpling upon compression. Dermoscopic examination often reveals a faint network around a pale central area, sometimes featuring white lines and brown holes, known as a negative network. Crystalline structures, appearing as shiny white lines, are commonly observed under polarised dermoscopy.

Haemosiderotic dermatofibromas, a less common variant, consist of numerous small vessels and haemosiderin deposits, both intraand extracellular. Dermoscopy shows a multicomponent pattern with a central bluish or reddish area, white or yellowish structures, and a peripheral pigment network.

Neurofibroma Dermoscopy

Solitary neurofibromas can be misdiagnosed as dermal nevi or skin tags due to their soft to firm nature. The buttonhole sign, where the lesion is pushed through a dermal defect and rebounds upon release, is a helpful diagnostic feature. Dermoscopically, these appear as featureless nodules.

Lichenoid Keratosis Dermoscopy

Lichenoid inflammation affecting solar lentigos or seborrhoeic keratoses results in localized melanocyte destruction and free dermal melanin or melanin within melanophages, appearing as granular grey dots. While grey dots can also be seen in melanomas, lichenoid keratoses lack a pigment network and typically present amorphous areas without the features of seborrhoeic keratosis.

Porokeratosis, Sebaceous Hyperplasia, and Viral Warts Dermoscopy

Porokeratosis is characterized by a cornoid lamella, with occasional prominent follicular plugging. Sebaceous hyperplasia is marked by pale yellow lobules around a central follicular opening, with common telangiectasia that contrasts with the irregular vessels seen in basal cell carcinoma. Viral warts present a lobular structure, sometimes with a central thrombosed capillary, and interrupted normal dermatoglyphics.

Epidermal Nevus and Cysts Dermoscopy

Epidermal nevi resemble seborrhoeic keratoses or viral warts but are uniform and appear within the first decade of life. Cysts, upon close inspection, reveal a follicular opening.

Clear Cell Acanthoma and Trichoepithelioma Dermoscopy

Clear cell acanthoma exhibits multiple pinpoint or dotted vessels in a string of pearls arrangement. Trichoepitheliomas and trichadenomas, benign hair follicle tumors, show multiple white clods, aiding in their distinction from basal cell carcinoma.

Inflammatory Dermatosis Dermoscopy

Dermoscopy can identify red scaly plaques through vascular patterns, such as atypical vascularity in amelanotic melanoma, arborising telangiectasia and ulceration in superficial basal cell carcinoma, and grouped glomerular vessels in squamous cell carcinoma in situ.

Skin Infestations and Miscellaneous Uses

Entodermoscopy aids in identifying scabies mites and their faeces within burrows, characterized by distinct head shapes. It also confirms the presence of nits in pediculosis capitis, with filled and empty cases having distinct appearances.

In summary, dermoscopy offers a comprehensive approach to diagnosing a wide array of non-melanocytic skin lesions, providing detailed visual information that enhances clinical assessment and aids in accurate diagnosis.