Sunday, August 29, 2010

Which dermatoscope should I buy? and Using my Dermatoscope

Since the above was written Heine have updated the Delta 20 to have 
both polarised and non polarised light.  See the Heine website

There is also now a DL4 dermatoscope from 3Gen. Magnetic rings allow easy coupling of small digital cameras to the dermatoscope to record images. See Australian DL3 distributer

You can also get attachments for smartphones from both Heine and 3Gen but I still prefer a dedicated setup.

Using your Dermatoscope

If someone has previously had a melanoma try to examine all pigmented lesions on their skin and any new pink lesions.

If the pigmented lesion is symmetrical and one colour move on. Look carefully at all dark pigmented lesions and any with varying pigmentation and all large pigmented lesions.

On the face with a pigmented lesion look for grey circles or partial grey circles as they often point to a lentigo maligna.

On the feet look at the edge of the pigmented lesion. If the pigment is in the furrows then the lesion is a benign acral nevus. Don’t concern yourself with the centre of the lesion which might be lattice or fibrillar. If however the edges show ridge pigmentation you have either an acral melanoma or subcorneal bleeding.

Look for polygons in large pigmented lesions on the trunk. They certainly should have you thinking of a lentiginous melanoma.

Pink raised lesions could be an amelanotic melanoma so look for polymorphous vessels but if ulceration consider BCC more likely with linear irregular vessels and sometimes white lines. White lines are also a feature of desmoplastic melanomas.  

Elevated pink growing lesions generally need to be excised irrespective of the dermatoscopy to exclude other tumours such as Merkel cell, Atypical Fibroxanthoma, Poorly differentiated SCC and skin metastases.

Pink flat lesions could be BCC (linear irregular branched vessels) , SCC in situ (dot or glomerular vessels), amelanotic melanoma (polymorphous and dot vessels , white lines)

The dermatoscope is best for diagnosing benign lesions. 

Hemangiomas have vascular globules or clods.

Seborrhoeic keratoses have orange, brown or white clods. There are a wide range of variants though and irritated light coloured se bks can look very like an SCC. Melanoacanthomas can be so dark you think they are melanomas. Clear cell acanthomas are pink with a distinctive vascular pattern.

Dermatofibromas have a white collagen centre with a surrounding reticular network looking like a pigmented lesion but there are other variants.

Adnexal tumours including warts are usually skin coloured and some are scaly. The dermatoscope can show the thrombosed capillaries of a wart but there are few specific dermatoscopic patterns for these tumours and histology is best to define them.

Some benign nevi are easier to diagnose dermatoscopically than others. The easy ones to diagnose are blue nevi, congenital nevi, Dermal nevi, Reed and Spitz nevi.  Clinically atypical nevi that are later diagnosed histologically dysplastic can have overlap features of a melanoma and are rightly excised.

The other common skin cancers are basal and squamous cell carcinomas. You don’t see a pigment network in a BCC  but pigmented BCCs will show dark blue clods of pigment and grey dots.

SCCs have lots of keratin especially when histologically well differentiated so look for looped vessels surrounded by keratin or white circles in hair follicles. The superficial in situ SCC or Bowen’s disease will show dot or glomerular vessels as its main dermatoscopic feature.

Lastly the dermatoscope can be used in medical dermatology in a wide range of diseases to assist in the clinical diagnosis.