By Dr Ernest Allan, Honorary Consultant Clinical Oncologist

Litigation as a result of delay in the diagnosis of malignant melanoma occurs frequently. It may arise from the failure of the GP, the dermatologist or the pathologist.

Malignant melanoma may arise de novo as a small black speck which gradually progresses to a substantial tumour. Alternatively, and more usually, it arises from a naevus which may have been present for many years.

NICE and the BAD have issued guidelines to enable GPs and dermatologists to identify malignant melanomas and to differentiate them from benign skin lesions. Members of the legal profession tend to rely on these guidelines.  As a result clinicians either discharge patients who do not have the characteristic features of malignant melanomas or keep them on follow up until the characteristic features develop.

Patients frequently present as the horizontal growth phase is changing to a vertical growth phase. At this time no features of malignancy may be apparent.

The Breslau thickness and the presence of lymph node involvement are the two most important prognostic features. As the tumour enters the vertical growth phase the lesion may have a Breslow thickness of 0.5 mm with a 10 year survival of 95%. When the Breslau thickness is allowed to progress to more than 4mm the 10 year survival falls below 50%.

For each mm increase in Breslow thickness there is a 13% increase in the risk of metastatic disease. The growth rates of Breslow thicknesses are variable but may be as rapid as 0.5 mm per month during the vertical growth phase.

The only safe procedure is to excise all pigmented lesions when the patient gives a history of change.

As a result of this many benign lesions would be excised but there would be a substantial reduction in mortality from malignant melanomas and litigation from missed melanomas would become a feature of the past.

For a broader look at delayed diagnoses in oncology and their legal implications, see Litigating Delayed Diagnosis of Lung Cancer.

Relying on the naked eye or dermascope appearance of a pigmented lesion may delay the diagnosis and reduce the chances of cure. A long-standing pigmented lesion that is exhibiting features of change or a new pigmented lesion that is increasing in size should be assumed to be malignant melanoma until proved otherwise.

Diagnostic delays aren't exclusive to skin cancer. Our post on Legal Insights into Sarcoma explores similar medico-legal challenges in soft tissue cancers.

Backwards Extrapolation of Breslow Thickness

The courts accept backwards extrapolation of the Breslow thickness in an attempt to assess the Breslow thickness when there was a failure to identify the lesion as a malignant melanoma.

However the rate of progression of the Breslow thickness, as published in peer review journals, is based on one measurement after excision and an estimate by the patient as to when the lesion first appeared and when it changed in character. In addition the Breslow thickness increases at a faster rate during the vertical growth phase than during the radial growth phase.

Therefore it must be accepted that estimates of the Breslow thickness by backwards extrapolation are basically unsound. A description of the lesion and its change in appearance over time as described by the claimant or relatives remains the optimum way of assessing the Breslow thickness at the time of the breach of duty of care.

About the Author:

Dr Ernest Allan is an Honorary Consultant Clinical Oncologist at The Christie Hospital one of the largest and most prestigious cancer treating institutes in Europe. He retired from clinical work in 2019, however has an honorary appointment to enable him to continue his research.

Dr Allan spent over 40 years at the Christie's and is therefore experienced in the management of all forms of cancer and able to comment on these claims. He has been undertaking medico-legal work for 20 years.

Dr Allan can be contacted for all medico-legal work and to request his CV at ernestallan@inneg.co.uk