Missed skin cancer diagnoses: when a small mole becomes a serious concern
Skin cancer, particularly melanoma, is one of the most common and potentially life‑threatening cancers in the UK and worldwide. While many skin lesions are entirely harmless, the ability to distinguish between a benign mole and a malignant melanoma is critical.
Melanoma is highly treatable when detected early, with excellent survival rates; however, a delay in diagnosis can allow the cancer to spread, dramatically worsening the outcome. For patients, a missed or delayed diagnosis may not only carry devastating health consequences but can also raise serious medico‑legal questions about whether the standard of care was met.
Skin cancer red flags
A harmless mole, or melanocytic naevus, typically appears as a small, symmetrical, evenly coloured spot with well‑defined borders. These lesions tend to remain stable over time. In contrast, melanoma often presents with warning signs that can be remembered using the ‘ABCDE’ criteria:
- asymmetry;
- border irregularity;
- colour variation;
- diameter greater than 6mm; and
- evolution or change in size, shape, or colour.
Additional red flags include itching, bleeding, crusting, or a lesion that looks markedly different from others (‘the ugly duckling’ sign). Recognising these distinctions is essential for both patients and clinicians, as subtle differences can signal a potentially aggressive cancer.
Diagnosing skin cancer
GPs play a vital frontline role in identifying suspicious skin lesions. When a patient presents with a changing mole or unusual lesion, a GP is expected to carry out a careful clinical assessment, often supported by dermatoscopy if trained. If there is any suspicion of melanoma, prompt referral through an urgent suspected cancer pathway, typically within two weeks, is required under national guidelines. Where uncertainty remains, GPs should err on the side of caution, ensuring appropriate follow‑up, documentation, and safety‑netting advice so that no suspicious lesion is overlooked.
Initial investigations
A suspicious mark or mole on the skin is investigated through a careful, step‑by‑step medical process aimed at identifying whether it is cancerous as early as possible. The process usually begins with a thorough clinical assessment by a GP or dermatologist.
During this examination, the clinician will look closely at the lesion using recognised warning signs such as asymmetry, irregular borders, multiple colours, size, and any recent changes. They will also ask about how long the lesion has been present, whether it has evolved, and whether there are symptoms such as itching, bleeding, or crusting. In addition, the wider skin area may be examined, and nearby lymph nodes checked, to ensure there are no other concerning features.
In many cases, the clinician will use a dermatoscope, which is a specialised handheld device that magnifies the skin and illuminates structures beneath the surface. This allows for a more detailed assessment than is possible with the naked eye and can help distinguish benign lesions from those that are more suspicious. Dermatoscopy is a valuable tool, but it relies on proper training and experience to interpret the findings accurately.
Referrals for further investigation
If the lesion raises any suspicion of melanoma or another skin cancer, the patient should be referred promptly to a specialist, typically through an urgent suspected cancer pathway. This system is designed to ensure that individuals with potentially serious skin lesions are assessed quickly by dermatology experts, minimising any delay in diagnosis.
The most important step in confirming whether a lesion is cancerous is a biopsy. In many cases, this involves removing the entire mole or mark under local anaesthetic in a procedure known as an excision biopsy. This approach allows the laboratory to examine the full lesion under a microscope and determine not only whether cancer is present, but also its type and characteristics. For melanoma, one of the most critical factors assessed is the depth of the tumour within the skin, as this has a direct impact on staging and prognosis.
Treatment for skin cancer
If cancer is confirmed, further treatment and investigations may be required depending on how advanced it is. This can include additional surgery to remove a margin of surrounding tissue and, in some cases, tests to determine whether the cancer has spread to nearby lymph nodes or beyond. However, when a lesion is identified and treated early, the initial biopsy may also serve as definitive treatment, particularly for very early melanomas.
Missed or delayed diagnoses
The entire process is designed to ensure that suspicious lesions are identified, referred, and diagnosed without delay. When these steps are followed appropriately, the chances of detecting skin cancer at an early, highly treatable stage are very high.
Conversely, any failure to properly assess, investigate, or refer a suspicious lesion can lead to delayed diagnosis, which may allow the cancer to progress and significantly affect the outcome.
Medical care can fall short when symptoms are dismissed, examinations are rushed or incomplete, or follow‑up arrangements are not made. In some cases, patients report being reassured without adequate assessment, or not being referred despite clear warning signs. These failures can lead to delayed diagnosis, during which time melanoma may progress from a localised, curable lesion to an advanced cancer requiring more invasive treatment, such as lymph node dissection, immunotherapy, or chemotherapy. Tragically, late‑stage melanoma is associated with significantly poorer survival outcomes.
The prevalence of melanoma continues to rise, making awareness and vigilance more important than ever. When diagnosed early, surgical excision alone is often curative, and patients can expect excellent long‑term survival. This stark contrast between early and late diagnosis highlights why timely and appropriate medical care is so crucial. A missed opportunity to diagnose melanoma early can transform a straightforward procedure into a life‑altering or even life‑threatening condition.
If you or a loved one has experienced a delayed diagnosis of skin cancer, it may be appropriate to explore whether medical negligence played a role. A medical negligence investigation can help secure answers, access compensation for the harm caused, and drive improvements in patient safety.
Case study
Penningtons Manches Cooper is experienced in representing patients after a delayed diagnosis of melanoma and settling claims for them. One such case was for a woman in her 50s who developed a worrying mark on her face, but was reassured more than once by her GP that it was nothing concerning, and only a harmless blemish. However, the mark was unusual for her, had steadily increased in size and prominence, had partially deepened in colour, and looked different to the other moles she had.
Some months passed before, eventually, our client was referred for further investigations, very much due to her own persistence. The mark was biopsied and a diagnosis of melanoma reached. Thankfully, the malignancy had not spread, and the melanoma could be treated by surgical removal. Following the biopsy, a further operative procedure was necessary to ensure complete removal with clear margins. This required more extensive removal of tissue and left our client with visible facial scarring.
Our expert evidence, from independent GP, dermatology and oncology experts, was that there had been a failure by the GP to make a two-week referral for cancer investigations, and that had that happened, it would have led to a biopsy and an earlier confirmation of the diagnosis, at a time when the melanoma was smaller and shallower, such that surgical removal would have been easier and completed leaving virtually invisible scarring.
Alison Johnson, a partner in Penningtons Manches Cooper’s medical negligence team, served a letter of claim on the defendant and even though that was met with a denial of liability, disclosure of selected evidence on a ‘without prejudice’ basis, in support of a settlement offer, led to settlement negotiations and a successful conclusion to the claim. The damages awarded were relatively modest, reflecting the fact that thankfully the cancer was still caught before it had spread and that our client’s surgery was considered curative, but this still provided her with the answers she was looking for and an acknowledgement of the anxiety and more extensive surgery she had undergone, and the ongoing worry of disease recurrence she still had.
Alison comments: “Because facial melanomas can be easily overlooked or misdiagnosed, any persistent or changing lesion on the face should be assessed promptly by a healthcare professional. Early identification is crucial, as at this point treatment is usually straightforward and highly effective, whereas delays can allow the melanoma to grow deeper into the skin and spread, leading to more advanced cancer.”