Imaging for Borderline Lesions: Reducing Unnecessary Biopsies

By Dr Maxton Bergin

A mole or skin spot does not always look clearly harmless or clearly cancerous. Some lesions sit in a diagnostic grey zone: they have one or more unusual features, but not enough information is available from a routine examination to confidently decide whether they need a biopsy straight away.

Doctors may describe these lesions as borderline, equivocal or indeterminate. In this context, these terms do not mean that a lesion is “halfway” between benign and cancerous, or that it is a specific pathological diagnosis. They simply mean that its appearance creates genuine diagnostic uncertainty.

When uncertainty remains, a biopsy is often the safest and most appropriate option. A biopsy removes tissue for histopathology—laboratory examination of tissue under a microscope. Histopathology remains the definitive method when a tissue diagnosis is needed.¹˒⁴

However, for selected lesions, advanced non-invasive imaging can provide additional information before a decision is made. Dermoscopy and reflectance confocal microscopy (RCM), also called optical biopsy, can help a doctor decide whether a lesion appears suitable for monitoring, needs a biopsy, or requires further specialist assessment.¹⁻³

The aim is not to avoid biopsies at all costs. The aim is to make better-informed decisions: to perform a biopsy promptly when it is clinically necessary, while potentially avoiding procedures that are unlikely to add meaningful benefit for lesions that can be assessed or monitored safely.

What is a borderline or equivocal skin lesion?

A borderline, equivocal or indeterminate skin lesion is a mole, spot or patch of skin that does not have a clearly benign appearance but also does not show enough definite warning signs to make the next step obvious.¹˒²

This can happen for several reasons:

Benign moles can have unusual pigment patterns.
Early melanoma may look subtle.
Sun damage can create irregular colour and structure around otherwise harmless spots.
Facial lesions can look different from lesions on the trunk or limbs.
Inflammation, trauma, previous treatment or scarring can alter the appearance of a lesion.
Some skin cancers do not follow the “typical” visual patterns that patients may have seen in public health information.⁴˒⁵

A doctor may be uncertain even after a careful visual examination. This is not a failure of the examination; it reflects the fact that some skin lesions genuinely overlap in appearance.

Why clinical examination alone is sometimes not enough

Clinical examination is the essential starting point for any skin lesion. Your doctor considers the lesion’s colour, shape, border, size, symptoms, growth pattern and location, as well as your personal and family history of skin cancer.⁴˒⁵

However, the naked eye cannot show the detailed pigment structures, blood vessels and cellular patterns found within the skin. That is why doctors may use dermoscopy and, for selected uncertain lesions, reflectance confocal microscopy.¹⁻³

These tools provide different layers of information. They can increase diagnostic confidence, but they do not make clinical judgement unnecessary. A lesion that is changing, bleeding, ulcerated, growing quickly or strongly suspicious on examination may need biopsy without delay.⁴˒⁵

What is dermoscopy?

Dermoscopy is a painless close-up examination that uses magnification and specialised polarised light to look beneath the skin’s surface. It helps doctors see pigment patterns, structures and blood vessels that are not visible with the naked eye.⁶

Dermoscopy improves diagnostic accuracy for melanoma and other skin cancers compared with visual examination alone, particularly when used by trained clinicians.⁶˒⁷ For many lesions, dermoscopy provides enough information to decide whether the spot appears benign, needs monitoring or should be biopsied.

But dermoscopy does not always resolve uncertainty. This is especially true for subtle pigmented lesions, lesions on chronically sun-damaged facial skin, and lesions with mixed or unusual features.¹˒²

What is reflectance confocal microscopy?

Reflectance confocal microscopy, or RCM, is a non-invasive imaging technique that uses a low-power laser to create highly magnified images of living skin. It is sometimes described as an optical biopsy because it can show skin structures at approximately cellular-level resolution without cutting or removing tissue.¹˒³˒⁸

During an RCM examination, a small imaging head is placed gently against the skin. The device captures horizontal images at several levels through the epidermis and upper dermis—the top layers of the skin. The test does not involve needles, scalpels or stitches.¹˒³˒⁸

RCM does not provide the same information as histopathology. It cannot assess all skin depths, and it cannot fully replace the examination of tissue removed by biopsy. However, it can provide useful additional detail for selected lesions that remain uncertain after dermoscopy.¹⁻³

How dermoscopy and RCM work together

Dermoscopy and RCM are complementary rather than competing tests.

Clinical examination considers the whole person: symptoms, lesion history, risk factors and the broader skin examination.
Dermoscopy provides magnified pattern information from the lesion.
RCM provides additional cellular-level detail from the upper skin layers.
Biopsy and histopathology provide the definitive tissue diagnosis when required.¹⁻⁴˒⁶

In practice, RCM is most useful as a second-level assessment when a lesion remains equivocal after clinical examination and dermoscopy.¹˒² It may increase confidence that a lesion has reassuring features, or it may identify concerning features that support biopsy.

This approach can be particularly helpful where a biopsy would be technically difficult, cosmetically significant or more likely to affect function—but only if the lesion is suitable for imaging and the treating doctor considers non-invasive assessment clinically appropriate.

Can imaging reduce unnecessary skin biopsies?

Yes, in carefully selected equivocal lesions, adding RCM to clinical examination and dermoscopy can reduce the number of benign lesions that are removed unnecessarily.¹⁻³˒⁹

A large randomised clinical trial involving 3,165 patients found that using RCM alongside standard assessment reduced the number of lesions excised for each melanoma detected by 43.4%. The study also found that RCM improved the proportion of removed lesions that were melanoma rather than benign lesions.⁹

Another prospective study found that using RCM as a second-level examination for equivocal lesions saved more than half of benign lesions from unnecessary excision in that setting.¹⁰

These findings need careful interpretation. They do not mean RCM is perfect or that every uncertain mole can be safely left alone. They mean that, when used by trained clinicians for appropriate lesions, RCM may increase specificity—the ability to correctly recognise benign lesions—and therefore reduce avoidable excisions.¹˒²

A Cochrane review found that, in studies of equivocal lesions, RCM had higher specificity than dermoscopy while maintaining similar sensitivity. In plain language, RCM was better at identifying some benign lesions that did not need removal, but neither test detected every melanoma.¹

This is why clinical judgement and appropriate follow-up remain essential.

Why avoiding an unnecessary biopsy can matter

A skin biopsy is a valuable medical procedure when it is needed. It can confirm a diagnosis, determine tumour depth and subtype, and guide the safest treatment.⁴˒⁵

However, when a lesion is benign, avoiding an unnecessary biopsy may have practical benefits:

avoiding a scar;
avoiding local anaesthetic and a minor surgical procedure;
avoiding wound care and time off work or activities;
reducing small risks such as bleeding, infection or delayed healing;
avoiding tissue removal from cosmetically sensitive areas;
reducing inconvenience and unnecessary healthcare use.⁵˒¹¹

These benefits can be particularly relevant on the face, nose, eyelids, lips and ears, where scars may be more noticeable or where anatomy is delicate.¹¹

The goal is never to discourage an appropriate biopsy. If a lesion is suspicious or imaging remains uncertain, the value of obtaining a tissue diagnosis outweighs the downsides of the procedure.

Borderline lesions on the face and other sensitive areas

Non-invasive imaging can be particularly useful for selected lesions on cosmetically or functionally sensitive parts of the body. This includes the face, nose, eyelids, lips, ears and some areas of the hands and feet.¹¹˒¹²

On sun-damaged facial skin, benign pigmentation, early melanoma and other lesions can share similar features. A biopsy may still be required, but RCM can sometimes provide additional information before surgery or help identify the most informative area to sample.³˒¹²

When is a biopsy still necessary?

A biopsy should not be delayed when a lesion has features that make tissue diagnosis clinically necessary. This may include:

strong clinical or dermoscopic suspicion of melanoma or another skin cancer;
rapid growth, bleeding, ulceration or a persistent non-healing area;
a lesion that appears thick, nodular or likely to extend deeper than RCM can assess;
a lesion with concerning symptoms or significant change;
an imaging result that remains equivocal;
a situation where tumour subtype, depth or margin information is needed for treatment planning.⁴˒⁵˒¹³

RCM mainly images the epidermis and upper dermis. It is less useful for lesions that are very thick, heavily crusted, ulcerated or located in positions that cannot be imaged reliably.³˒⁸˒¹³

If imaging raises concern, or if the doctor cannot confidently exclude cancer, biopsy remains the appropriate next step. Histopathology is still the reference standard for confirming many skin cancer diagnoses.⁴˒¹³

What happens if imaging is still uncertain?

If dermoscopy and RCM do not provide a clear answer, the safest options are usually biopsy or planned short-term monitoring, depending on the lesion and the clinical context.¹˒²˒⁴

Short-term monitoring is not simply “doing nothing.” It involves a deliberate plan to re-examine and re-image the lesion at a defined interval, looking for objective change. This approach is only appropriate when the treating doctor considers the immediate risk to be low enough and when reliable follow-up is possible.⁶˒⁷

A lesion should not be monitored solely because a patient wants to avoid a biopsy. The decision must be based on medical assessment, imaging findings, risk factors and the potential consequences of waiting.

How Skintel supports diagnostic decision-making

Skintel is a specialist diagnostic skin imaging service, not a treatment clinic. Its role is to provide additional diagnostic information to help referring doctors make well-informed decisions about lesions that may be benign, suspicious or uncertain.

At Skintel, dermoscopic and confocal images are reviewed by an experienced skin cancer doctor. Imaging findings are incorporated into a clinical report and communicated to the referring doctor. Your GP, dermatologist or surgeon remains responsible for discussing the results, arranging biopsy or treatment where required, and planning ongoing management.

Skintel does not use imaging simply to avoid biopsies. Imaging is used to help identify lesions that require biopsy promptly and, in selected cases, to provide enough information for a treating doctor to consider non-invasive assessment or monitoring instead.

Frequently Asked Questions

Can a suspicious mole be checked without a biopsy?

Yes, some suspicious or equivocal moles can be assessed first with dermoscopy and, in selected cases, reflectance confocal microscopy.¹˒² These tests may provide enough additional information to guide monitoring or reassure the treating doctor. However, a biopsy is still required whenever the lesion remains concerning, cannot be assessed adequately with imaging, or needs a definitive tissue diagnosis.⁴˒¹³

Can confocal microscopy prevent unnecessary biopsies?

Confocal microscopy can reduce unnecessary biopsies in selected equivocal lesions by helping clinicians recognise some benign patterns more confidently.¹˒²˒⁹ It does not prevent all biopsies, and it should never be used to avoid a biopsy that is clinically necessary. The purpose is better diagnostic decision-making, not simply reducing the number of procedures.

How accurate is an optical biopsy?

Optical biopsy, or RCM, is a useful and accurate second-level imaging test for selected skin lesions, but it is not perfect. A Cochrane review found that RCM can improve specificity for equivocal lesions compared with dermoscopy, meaning it may reduce some benign excisions.¹ However, RCM can miss lesions and is limited to the upper skin layers, so biopsy remains necessary in appropriate cases.

Can a doctor tell if a mole is cancerous without removing it?

Sometimes a doctor can be sufficiently confident based on examination, dermoscopy and imaging to recommend monitoring rather than immediate removal.¹˒²˒⁶ However, no non-invasive test can provide certainty in every lesion. When cancer cannot be confidently excluded, or when information about tumour depth or subtype is needed, biopsy and histopathology remain necessary.⁴˒¹³

Does every suspicious mole need to be biopsied?

No, not every lesion that initially looks unusual needs immediate biopsy. Some lesions can be clarified with dermoscopy, RCM or planned short-term monitoring.¹˒²˒⁶ However, lesions with strong warning signs, significant change or persistent uncertainty should be biopsied.⁴˒⁵ The decision depends on the lesion, its location, your risk factors and your doctor’s assessment.

What happens if dermoscopy is inconclusive?

If dermoscopy is inconclusive, the doctor may use RCM, compare photographs over time or recommend biopsy.¹˒² The appropriate next step depends on how concerning the lesion appears and whether it can be safely monitored. If there is meaningful concern for melanoma or another skin cancer, biopsy is generally the safest option.⁴˒⁵

Can confocal microscopy diagnose melanoma?

Confocal microscopy can identify cellular patterns that may support or raise concern for melanoma, especially in lesions that remain equivocal after dermoscopy.¹˒²˒³ It is an adjunct to clinical assessment, not a universal replacement for biopsy. If RCM findings are concerning or uncertain, a biopsy is usually needed to confirm the diagnosis and guide treatment.⁴˒¹³

When is a skin biopsy still necessary?

A skin biopsy is necessary when a lesion is strongly suspicious, is changing rapidly, bleeds or ulcerates, is thick or difficult to image, or remains uncertain after non-invasive assessment.⁴˒⁵˒¹³ Biopsy is also needed when histopathology is required to confirm the tumour type, depth or other features that influence treatment.

Is optical biopsy painful?

No. Reflectance confocal microscopy is generally painless because it uses a small contact imaging head and low-power laser rather than needles or cutting instruments.³˒⁸ You may feel gentle pressure against the skin, but there is no wound, stitch or recovery period. If biopsy is still needed after imaging, your treating doctor will explain the procedure and local anaesthetic.

Can a suspicious mole simply be monitored?

Sometimes, but only when a doctor believes that short-term monitoring is medically safe and likely to provide useful information.⁶˒⁷ Monitoring involves a planned review with repeat examination and images, not ignoring the lesion. A mole should not be monitored if it is highly suspicious, changing significantly or cannot be assessed reliably.

Conclusion

Borderline skin lesions are common because benign and malignant conditions can overlap in appearance. Clinical examination and dermoscopy remain the starting point, while reflectance confocal microscopy may provide valuable additional information for selected equivocal lesions.

For appropriate cases, advanced imaging can help doctors distinguish lesions that need biopsy from those that may be suitable for careful monitoring. This may reduce some unnecessary biopsies, especially in cosmetically sensitive locations, without compromising the need for prompt biopsy when cancer is suspected.

The goal is not fewer biopsies at any cost. It is the right biopsy, for the right lesion, at the right time.

Disclaimer

All information is general and not intended as a substitute for professional advice.

References

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