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The role of Mohs excision in periocular basal cell carcinoma
  1. E A Barnes1,
  2. A J Dickinson1,
  3. J A A Langtry2,
  4. C M Lawrence2
  1. 1Department of Ophthalmology Royal Victoria Infirmary Newcastle upon Tyne NE1 4LP, UK
  2. 2Department of Dermatology Royal Victoria Infirmary Newcastle upon Tyne NE1 4LP, UK
  1. Correspondence to: MrEric A Barnes Department of Ophthalmology Royal Victoria Infirmary Newcastle upon Tyne NE1 4LP, UK; eric.barnes{at}nuth.nhs.uk

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We read with interest the paper by Hamada et al,1 which draws a number of conclusions from a 5 year follow up study of 69 periocular basal cell carcinomas (BCCs) treated by conventional surgery and, in particular, suggests that there is no place for Mohs micrographic surgery (MMS) in patients with periocular BCCs. MMS is the serial saucerisation excision with mapped horizontal tissue sections examining 100% of the surgical margins to produce histological evidence of tumour negative margins. Unfortunately, the data included in the paper are incomplete and if such conclusions are to be considered, then further clarification is required.

Risk of BCC recurrence relates directly to the nature of the tumours treated.2 The principal risk factors for recurrence include previous treatment, large tumour size, and an infiltrative or micronodular histological growth pattern. No information is given on the first two factors and the histological subtype was non-specified in approximately 45% of cases. We calculate from the data provided that the authors experienced a 19% 5 year recurrence rate in patients with a histologically infiltrative BCC.

If most of the “non-specified” tumours in Hamada’s series were small nodular tumours, as the paper implies, then Hamada’s series also differs significantly from other larger series in that it represents a group of patients with an inherently better prognosis. Other comments hint at this, in that 76% of BCCs were on the lower eyelid and 72% were amenable to direct closure. If the majority of the tumours in this series were not in a high risk group then only one recurrence would be anticipated. In contrast, the Australian Mohs’ database series3 reported on a much higher incidence of high risk tumours (50% were infiltrative, morphoeic, basosquamous, or superficial), of which only 54% were on the lower eyelid while 41% affected the medial canthus, a site with a proved higher risk of recurrence. Despite this, they reported a 0% recurrence rate for primary BCCs of all histological subtypes treated by MMS surgery.

Hamada et al also conclude that 4 mm margins are justified for well defined nodular tumours, on the basis of the 5 year recurrence rates and the fact that most eyelids can still be directly repaired after such excisions. It is of interest, however, that 16% of the patients reported had incomplete tumour excision at the first attempt, although we do not know what margins were used for this group. As conventional pathological sectioning examines less than 1% of the margins,4 it is likely that the actual incomplete excision rate was higher. Hamada et al argue that MMS is not necessary for periocular tumours on the basis that it is difficult to obtain true MMS sections. Unless either periosteum or anterior orbital septum are breached by the tumour, then there is no evidence for the former statement. What about cost benefit? MMS histology costs are greater than routine sections. However, when the other advantages of MMS are taken into account MMS is cost effective in comparison with traditional surgical excision.5

The current best evidence shows that recurrence rates are lower with MMS than with any other technique, with MMS for recurrent or high risk tumours showing the greatest advantage over conventional surgery. Furthermore, Hamada et al acknowledge that the tissue sparing quality of MMS is an important issue in that 36% of patients will develop a second BCC within 5 years.

Although we believe that MMS is the treatment of choice for optimal cure rates in periocular BCC, we would agree with Hamada et al that is currently impractical for all tumours because of the patchy availability of the service in the United Kingdom. However, we believe the current evidence shows that MMS remains the optimal treatment for all high risk tumours based on treatment status, site, size, and histological subgroup and do not think that the data presented warrant a different conclusion.

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