Dear Editor,

We thank Barnes et al for their interest in our study and for affording us the opportunity to correct some misinterpretations that others may also have made regarding our paper.

We agree entirely that histological examination of the complete excision surface as suggested by Mohs would be the ideal one should aim at and that it would be superior to conventional bread loaf histological sectioning. We dispute that this is realistically possible in inhomogeneous and exceedingly mobile eyelid tissues unless they are fixed prior to excision as in the chemosurgery that Mohs originally described.

Trying to cut a complete 2mm thick saucer of tissue through fresh skin, orbicularis, tarsal plate, orbital septum and fat and then transferring it without distorting the relative tissue orientation is a challenge that few are equal to. It might have been helpful if Barnes et al had shared their practical experience of the technique with us in their letter.

That the risk of BCC recurrence relates to the tumour type is not in dispute and is indeed born out in our results. But it is helpful of Barnes et al to remind other readers of this fact. Histological subtype was not specified in the greater portion of our series as our histopathologists only pass comment when BCCs are infiltrative or unusual in other respects. We apologise for not stating this explicitly as it has clearly led to some misunderstanding.

However there is no justification for Barnes et al's assumption that the 'non-specified' tumours were small because 72% were managed by direct closure. We have clearly failed to get over a most important point. Direct closure under tension is not only possible in much larger lid defects than conventionally taught but also gives far superior functional and cosmetic results. As such we urge others to use this method of repair more widely.

That 76% of our tumours occurred on the lower lid should not come as a surprise to anyone as it is a well recognised fact. It does not suggest that our series is in any way biased.

That our series differs from the selected series in the Australian Mohs database is self evident. We described our experience with an unselected consecutive series of 223 secondary and tertiary periocular Basal Cell Carcinomas (BCC) referrals to a UK regional Oculoplastic service. Our case mix should therefore be representative of that in other similar UK units and our results are therefore more relevant to them than those of the high risk biased Australian Mohs series and our results can be used as an audit benchmark. Although we have used conventional non-Mohs treatment, we achieved a very low recurrence rate.

We fully support that full histological margin control, as in Mohs micrographic surgery, is the best treatment option in recurrent, high risk cases. Our study shows that careful non-Mohs BBC excision remains a valuable, safe and cost effective option. Our technique offered the patients with primary non-infiltrative BCC excellent cure rates and functional and cosmetic outcomes with no recurrence over 5 years follow up.

Correspondence to:
V T Thaller, FRCOphth
The Royal Eye Infirmary
Apsley Road
Plymouth
PL4 6PL
UK
vladimir.thaller@phnt.swest.nhs.uk

Dear Editor,

We read with interest the paper by Hamada et al 1, which draws a number of conclusions from a five year follow up study of 69 periocular 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 treated2. The principle 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 2 factors and the histological subtype was non-specified in approx 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 proven higher risk of recurrence. Despite this, they reported a 0% recurrence rate for primary BCCs of all histological subtypes treated by MMS surgery.

Hamada also concludes that 4mm 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 margins4, it is likely that the actual incomplete excision rate was higher. Hamada argues 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 to traditional surgical excision5.

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 acknowledges 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 that is currently impractical for all tumours because of the patchy availability of the service in the UK. 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 feel that the data presented warrant a different conclusion.

References

1. Hamada S, Kersey T, Thaller VT. Eyelid basal cell carcinoma: non- Mohs excision, repair and outcome. Br J Ophthalmol 2005;89:992-994

2. Lawrence CM. Mohs surgery - A critical review. Br J Plast Surg 1993, 46, 599-606

3. Malhotra R, Huilgol SC, Huynh NT, Selva D. The Australian Mohs Database, part II: Periocular basal cell carcinoma outcome at 5 year follow up. Ophthalmol 2004, 111, 631-636.

4.Abide JM, Nahai F, Bennet RG. The meaning of surgical margins. Plast Reconstr Surg 1984;73:492-6

5. Cook J, Zitelli JA. Mohs micrographic surgery: a cost analysis. J Am Acad Dermatol. 1998; 39:698-703.

EA Barnes¹, AJ Dickinson¹, J AA Langtry² and CM Lawrence²

¹Department of Ophthalmology Royal Victoria Infirmary Newcastle-upon-Tyne, NE1 4LP

²Department of Dermatology Royal Victoria Infirmary Newcastle-upon-Tyne, NE1 4LP

Competing interests: None to declare