Results

There were 157 malignant melanomas diagnosed in 156 patients (one patient having two synchronous malignant melanomas) during the six years of the study. The primary excision was carried out by GPs in 58 cases (37%), and by hospital specialists in 99 cases (63%) (dermatologists 38% and surgeons 25%) (table 1). Sixty three (40%) patients were male; 93 (60%) were female. The clinical diagnosis was malignant melanoma in five (9%) of the GP cases and 32 (35%) of the hospital specialist cases (table 2). In 25 (45.5%) of the GP cases and 35 (38%) of the hospital specialist cases the diagnosis was of suspicious pigmented lesion. A mole was diagnosed clinically in 22 (40%) of the GP cases and seven (8%) of the hospital specialist cases. Haemangioma or other diagnosis accounted for the remainder (three GP (5.5%) and 17 hospital specialist (19%)).

Histological examination showed a high percentage to be superficial spreading malignant melanomas (72% GP and 69% hospital specialist), accounting for 110 malignant melanomas (table 3). Nodular malignant melanomas accounted for 14 GP cases (24%) and 13 hospital specialist cases (13%). The remainder were lentigo maligna melanoma (two (4%) GP and 13 (13%) hospital specialist), acral lentiginous malignant melanoma (no GP and four (4%) hospital specialist), or spindle cell malignant melanoma (no GP and one (1%) hospital specialist).

The lateral excision margins were 2 mm or less in 41 (71%) GP cases and 50 (51%) of hospital specialist cases (table 4). A wider excision was performed in 89 (64%) of the 140 cases (89%) where this information could be ascertained. Forty (29%) of these were GP primary excisions. There was no histological evidence of residual melanoma in any of the wider excision specimens.

Fifty one (36%) were recorded as having had no wider excision; 11 (8%) being GP primary excisions and 40 (28%) being hospital specialist primary excisions. There was no information about such excision in a further 17 cases (seven GP and 10 hospital specialist). Of the total 68 cases where no wider excision could be confirmed, 24 (35%) had a primary excision margin of 2 mm or less; 10 were GP cases and 14 were hospital specialist cases. Most (53, or 78%) had a Breslow depth of 2 mm or less.

The Breslow depth was available in 152 cases; the remaining five being biopsies only. Three of the biopsies were nasal melanomas which could not be excised; in one case only the wide re-excision biopsy was received; the remaining case was referred elsewhere for plastic surgery. Where the depth was available 37 (64%) GP cases and 43 (46%) hospital specialist cases were less than 1 mm (table 5). Ten (17%) GP cases and 27 (29%) hospital specialist cases were 1–2 mm. Ten (17%) GP cases and 19 (20%) hospital specialist cases were 2.01–6 mm. The remainder were more than 6 mm: one GP (2%) and four hospital specialist (4%).

Almost half of the patients were under 50 years of age (74 or 47%). Almost three fifths (91 or 59%) of the malignant melanomas involved face, front and back of chest, arm or hand, the remainder involving abdomen or leg.

There were 63 patients (with 67 lesions) in the five year period, in whom the clinical diagnosis was of the malignant melanomas or suspicious pigmented lesion, but the histological diagnosis was of a benign condition (table 6). Of these, 24 patients (26 lesions) were from GPs and 39 patients (41 lesions) were from hospital specialists. Compound naevi accounted for eight (31%) of the GP cases and 11 (27%) of the hospital specialist cases. Seborrhoeic keratoses accounted for six (23%) of the GP cases and three (7%) of the hospital specialist cases. There were no dysplastic naevi in the GP cases but 10 (24%) in the hospital specialist cases. For the purposes of this study dysplastic naevi were classified as non-malignant and in the benign category. Haemangiomas accounted for only one (4%) of the GP cases, but five (12%) of the hospital specialist cases.

Discussion

The incidence of malignant melanoma in the Scarborough district is known to be significantly raised compared with West Yorkshire, and England, according to Yorkshire Cancer Organisation (now Northern and Yorkshire Cancer Registry and Information Service) figures, long acknowledged to be reliable.1 A relatively high proportion (almost two fifths) of malignant melanomas are primarily excised by GPs in this district, compared, for example, with south east Scotland where the figure is about 12%.5 For this reason, and to maintain groups of sufficient size for meaningful analysis, the decision was made to compare the two major groups of clinicians, GPs and hospital specialists, rather than to subdivide hospital specialists into surgeons and dermatologists, and compare three groups.

The proportion of male to female patients presenting with malignant melanoma (2:3) is within the expected range.6

This study confirms the findings of other studies that hospital specialists made a clinical diagnosis of malignant melanoma or suspicious pigmented lesion more often (73%) than GPs (54.5%), although in this study the difference is significantly less pronounced.5 7 8 Furthermore, hospital specialist cases were all primarily seen by GPs who, having made a diagnosis of malignant melanoma, may have decided on clinical grounds to promptly refer them.

The higher frequency where a “mole” was diagnosed by GPs (40%) compared with hospital specialists (8%) may well also reflect the referral of more clinically obvious cases to hospital specialists with the more equivocal pigmented lesions being dealt with by GPs.

Superficial spreading malignant melanoma was the most commonly diagnosed type in Scarborough as elsewhere5 8 accounting for 72% in the GP setting and 69% in the hospital setting. More nodular malignant melanomas were submitted by GPs (24%) than hospital specialists (13%) possibly reflecting relative ease of diagnosis and excision of this relatively uncommon type. In contrast only 4% of the GP submissions were lentigo maligna melanoma (the invasive form of lentigo maligna), compared with hospital specialists (13%), reflecting relative difficulty of excision due to site, rather than recognition, and hence higher referral to hospital of this type.

The lateral excision margins tended to be narrower with GP cases, being mostly 2 mm or less (71%) compared with 51% of hospital specialist cases, so confirming the findings of others.5 8 However, the margin was less than 1 mm in 16% of GP cases and a similar proportion (18%) of hospital specialist cases. A wider excision was subsequently performed in 89 of the cases (64%) where this information was available. We are aware of several cases where, for reasons of the anatomical site of the primary tumour or general health of the patient, a wider excision was not performed.

It is recommended that primary excision of melanoma should include a minimum lateral clearance of 2 mm together with a thin cuff of subcutaneous fat.9 10 Although there is no compelling evidence to date that incomplete primary excision predisposes to metastasis,11 provided further re-excision occurs within 30 days,11 12 this does allow accurate Breslow thickness to be measured and hence determination of width of re-excision.

Most malignant melanomas were 2 mm depth or less (Breslow thickness)5 8 whether excised by GP (81%) or hospital specialist (75%). There is therefore no evidence in this as in other studies5 8 that earlier lesions, as judged by this measurement, are being submitted in differing proportions by either group. It is also reassuring that most malignant melanomas are early (thin) at diagnosis. This confirms the findings of other groups and the trend over the last two decades for decreasing median melanoma thickness.13 Our findings do however suggest this trend may have reached a plateau.

In our experience only a very small proportion (around 1%) of all pigmented skin lesions biopsied were thought clinically to be a malignant melanoma or suspicious pigmented lesion, and shown histologically to be benign; GPs were no more likely than hospital specialists to do this.

All malignant melanomas are likely to initially be seen by GPs and each GP will make a decision as to whether to excise or refer to a hospital specialist. We have found no evidence to suggest that GPs in this area are not recognising and managing adequately skin lesions suspicious of malignant melanoma. This is all the more important in view of the high proportion of such lesions excised by GPs in Scarborough and the realisation that higher referral rates of pigmented lesions could overwhelm the hospital system. It is important that all GPs are aware of the clinical features of malignant melanoma. In general, lesions that are not obviously benign, or changing moles, should be seen by GPs and either removed in their entirety for pathological examination, or referred and dealt with by appropriately trained hospital specialists within four weeks. The vast majority of pigmented lesions submitted for histology are correctly diagnosed benign conditions, mostly naevi or seborrhoeic keratoses. Incisional biopsy may occasionally be acceptable, for example in the differential diagnosis of lentigo maligna or acral melanoma. Histological examination is mandatory in all cases.

What is disappointing is the sustained increase in incidence of malignant melanoma over the past six years. This will clearly necessitate continuation of prevention measures especially avoidance of sunburn in children, and limitation of total cumulative sun exposure in all white skinned individuals.

It is intended to continue this local audit of excised malignant melanomas in Scarborough, and recommended that such audit be carried out elsewhere to ensure optimum management whether by GP and/or hospital specialist. Early, accurate diagnosis offers the besthope for reduction in mortality, in advance of the long term goal of a reduction in incidence.

Learning points

Clinical features, Breslow tumour thickness, and diagnosis of malignant melanoma are shown in boxes 1, 2, and 3.