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Why did initial treatment not resolve the lesion on this man's lower back?

After initial treatment failed to clear this lesion, Dr Keith Hopcroft explains how he reached the right diagnosis

The patient

This 55 year-old-man presented on his wife's insistence – he had not noticed the skin lesion that had prompted her booking an appointment for him, nor was he bothered by it. She had spotted this macular patch on his lower back about two weeks previously. Neither of them had a clear idea how long it might have been there. It was not itchy, there were no skin lesions elsewhere and he was otherwise well. He had no significant history other than mild asthma and, in particular, he had never suffered any previous dermatological problem.

First instinct

A quick examination revealed a macular, slightly inflamed lesion in his lower lumbar region. It was around 1cm long by 1.5cm wide. I was struck by the prominent, active-looking edge and the central clearing, which made me think of a fungal infection.

Differential diagnosis

  • Tinea corporis
  • Eczema
  • Bowen's disease
  • Basal cell carcinoma (BCC).

Eczema is, of course, very common, and discoid eczema in particular can cause well-defined lesions of this sort. But with this diagnosis you would expect multiple lesions and itching, unlike the case here. And the usual distribution is on the limbs rather than the trunk.

Bowen's disease was certainly a possibility – unlike most forms of eczema this does present with solitary lesions. It is normally well defined and erythematous, too, which fitted this presentation. The only feature lacking was the typical scaling of Bowen's.

Any persisting, solitary skin lesion in a middle-aged patient should raise the possibility of a BCC. But this lesion was at an unusual site – the majority of BCCs are on the face – and there was no nodularity or ulceration. And, of course, we had no idea whether the lesion had just appeared or had been there for many months.

I favoured the fungal diagnosis and decided the response to treatment would help guide further action. So I prescribed clotrimazole cream, but shared with him my uncertainty and ensured he would return if the lesion did not clear.

The hidden clue

When he did return a few weeks later, I decided it was time for a closer look. This time with illumination, magnification and the benefit of hindsight, I was able

to convince myself that the ‘active edge' was in fact raised, rolled and pearly – a classical BCC, albeit in a slightly atypical position.

Getting on the right track

I referred my patient to the local dermatology unit. The clinical suspicion of BCC was confirmed on the histology of the excised specimen.

 

Dr Keith Hopcroft is a GP in Laindon, Essex

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