Benign or Malignant? Look for clues.
Patients presenting with solitary skin lesions can be a challenge for the podiatrist to diagnose – lesion recognition can be difficult. For most practitioners, our main concern is that we are not missing something malignant. Dermoscopy can be helpful in many cases but it is not universally practiced in podiatry. I recently read an article by Dr. Sara Ritchie  which was an excellent guide and have included her advice here, along with a few additional tips, which will be of relevance to podiatrists - even those without dermatoscopes.
1. A history is an important part of the assessment along with an examination of the lesion. Change reported by the patient is always an important indicator that warrants a careful assessment.
2. Always ask about family history of melanoma. If a patient has a first-degree relative (mother, father, brother or sister) who has had a melanoma this doubles their chances of developing one. If the patient has had a previous melanoma themselves, the risk of a second melanoma is increased tenfold.
Palpation is important to establish the lesion's texture but most importantly to determine if it is raised or flat. On the soles of the feet, dermoscopy is an integral part of the assessment but in other areas such as the dorsum, ankle and lower leg some basic principles can be helpful.
1. Palpation of the lesion can be helpful and give vital clues. If the lesion is soft, fleshy, wobbly or compressible it is likely to be benign. Malignant lesions tend to be firm. Examples of benign lesions include skin tags and dermal naevi.
2. Blanching is a sign of a benign lesion. If, when you place pressure on a lesion and it blanches completely, it is likely to be benign.
3. Is the lesion flat or raised? If a solitary lesion is palpable and the diagnosis is unclear, it should not be monitored but referred. For example, melanoma may begin with a horizontal growth phase but then move into a more aggressive vertical growth phase becoming readily palpable.
4. Dermatoscopic photographic monitoring in secondary care may sometimes be appropriate for flat lesions, which cannot be palpated at all. However, if the lesion is flat and shows other unusual signs (growth, multiple colours or changes) then dermoscopy is nearly always required on the feet and so if you are not trained in dermoscopy then an urgent referral for this should be considered anyway.
5. Rapid growth in a palpable lesion is always a red flag and should always be referred urgently. On the foot, pyogenic granuloma is an example of a benign rapidly growing, palpable lesion. However, even with these lesions, a diagnosis will need to be established histologically to rule out melanoma and so they should be referred urgently.
6. If you see pink, stop and think! Pink growing nodules anywhere on the skin should be referred urgently. A proportion of melanoma are hypopigmented and so lack pigment and look flesh coloured in appearance. The acronym “EFG” can be helpful as a reminder – Elevated, Firm and Growing is a red flag for any skin lesion.
7. Watch out for a single dark mole in a fair skin individual. Melanoma is more common in paler-skinned individuals. Always check to see if any other moles on the same patient have a similar appearance. Moles tend to look similar in an individual. The term ugly duckling is sometimes used to describe a “mole” that does not look like the others on the patient’s skin.
8. Colour counting. A naevus with any three different colours is suspicious, for example:
a. Pink, red and brown.
b. Pink, brown and black.
c. Blue, brown and black.
A naevus with 3 different colours is melanoma until proven otherwise and an urgent referral is warranted in these cases.
9. Even 2 different colours, such as blue and black, or pink and brown is suspicious and warrants dermoscopy. If that is not available a second opinion should be sought.
10. Beware of new “moles” in older patients. As we age, we stop developing melanocytic naevi so any new mole appearing in an older patient should be carefully assessed.
Plantar Specific Principles
1. For pigmented lesions on the soles, dermoscopy for small dark lesions is required to assess them properly.
2. As podiatrists we often observe cutaneous horns on the soles of the feet. Many of these are neglected hypertrophic corns. About 15% of cutaneous horns have a squamous cell carcinoma growing at the base, and these often have a thickened base. Any suspicious lesion of this type should be urgently referred.
3. Older patients who present with solitary, verrucous lesions on their feet should be carefully assessed. Squamous cell carcinoma is most common in older patients and may mimic verrucae. Any such solitary lesions with unusual features (exudation, bleeding, malodour or a bizarre keratinous appearance) should be referred urgently.
Referring a patient
In the UK, the usual pathway for any patient with a suspicious lesion is to be referred back to their general practitioner urgently. This can be done by contacting the GP by phone or letter stating the clinical findings and concerns (without speculation on the likely diagnosis). Inclusion of any images of the skin lesion or of a dermatoscopic image can also be helpful. A copy of the letter can also be given to the patient. It is also good practice to always ensure the patient has been followed up.
I wish to thank Dr. Sara Ritchie of the Primary Care Dermatology Society for allowing me to reproduce parts of the article here.
1. Ritchie, S., 20 Clinical Principles to help distinguish skin cancer from benign lesions. PCDS Bulletin, 2021. Spring Edition: p. 14-18.