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P. HARRINGTON, A. O’KELLY, I.A. TRAIL and A.J. FREEMONT
Centre for Hand and Upper Limb Surgery, Wrightington Hospital, Appley Bridge, Wigan, Lancs WN6 9EP, UK
Keywords: malignant melanoma, subungual melanoma, amelanotic melanoma, pyogenic granuloma, diagnostic delay
Between six and eight per cent of cases of malignant melanoma lack pigmentation on macroscopic examination, making accurate early diagnosis difficult. Delays in diagnosis and misdiagnosis are common in cases of subungual melanoma. We report a patient with an amelanotic subungual malignant melanoma who presented with a lesion that closely resembled a pyogenic granuloma. Since amelanotic melanoma usually presents as a vascular or ulcerating nodule, it should be considered in the differential diagnosis of a wide range of superficial lesions that occur in the hand
J.R.Coll.Surg.Edinb., 47 August 2002, 638-640
The incidence of malignant melanoma is increasing at a greater rate than any other type of malignant lesion. In recent years, early diagnosis and prompt surgical treatment have brought significant improvement in survival, such that the overall five-year survival now averages 80 percent.1 Between 6 and 8% of melanomas lack the typical pigmentation, making accurate early diagnosis difficult.2 Not surprisingly in many cases, amelanotic melanoma is initially incorrectly managed as a benign lesion.
Subungual melanoma is similarly rare, representing 2 to 3% of all malignant melanomas. The great majority of subungual lesion - (>90%) - occur on the thumb or great toe.3 Delays in diagnosis and misdiagnosis are common and the mean duration of survival for patients with a subungual lesion is significantly shorter than that for patients with melanoma at other sites.4
We report a case of amelanotic subungual melanoma which presented as a deep red nodule typical of a pyogenic granuloma, and we review the literature to highlight those clinical features shared by patients with subungal melanoma which should alert the clinician.
An 81 year old female was referred to the upper limb service at Wrightington Hospital with a non-healing lesion of the terminal pulp of the right middle finger. Six weeks previously, while working in the garden, she first noted that the nail plate had become distorted and raised at one side, and assumed that she had sustained a minor injury. During the intervening weeks the nail became more raised, the lesion bled occasionally after minor trauma; it had a sero-sanguinous ooze which stained the dressing and caused a superficial crust to form. She denied any associated pain.
Figure 1A Figure 1b: Clinical appearance of subungual lesion at initial presentation
Physical examination revealed a 2 by 2cm, deep red ulcerated nodule on the tip of the middle finger. (Figure 1a&b) Based on the clinical appearance a diagnosis of pyogenic granuloma was suspected and an incision biopsy was performed. Tissue specimens were sent for culture and routine histology. The wound was dressed and left to heal by secondary intention. Staphylococcus aureus was identified on culture and the patient was discharged on oral antibiotics.
The biopsy showed pleomorphic epithelioid cells arranged in loose packets. (Figure 2b) Tumour cells reacted with the melanoma marker HMB45 (Figure 2b) Residual tumour was identified. It contained some isolated areas of pigmentation. The tumour penetrated into the dense fibrous tissue beneath the nail bed to a depth of 0.5 cm.
Three weeks later, amputation of the digit was performed. There was no evidence of regional node involvement and screening for metastatic disease was negative.
The thickness of the lesion (Breslow depth) in millimetres is the single most important factor that determines the prognosis and treatment of a patient with malignant melanoma. Other important factors include the level of invasion (Clarke level), ulceration, host lymphocytic inflamatory response, mitotic index and growth phase.1 Subungual lesions are difficult to diagnose accurately and have been incorrectly diagnosed as paronychiae, benign naevi, fungal infections and traumatic lesions.1,3 Rigby and Briggs (1992) reviewed a series of 24 patients with subungual melanoma in the U.K. and found a mean diagnostic delay of 30 months.4 The mean five year survival ranged from 10 to 30%; this poor prognosis was related to the delay in diagnosis and the presence of advanced disease at the time of correct diagnosis being established.
Anatomic location of a malignant melanoma has previously been reported to be an important factor in determining prognosis in various studies.5,6 For example, Rogers et al (1983) suggested that melanomas on the hand and foot were associated with an inherently worse prognosis than those of an equivalent thickness at other sites.7 However, in most such studies, the lesions from various anatomic sites are grouped together, thus, confounding the possible importance of site.
More recent studies have examined the possible effect of the anatomic site of the lesion more systematically, and have concluded that the poorer prognosis for distal extremity tumours was due only to the more advanced clinical stage of the lesion at the time of presentation.1 Blessing et al (1991) reported a series of 100 patients with subungual melanoma in Scotland (two-thirds of whom were initially incorrectly diagnosed) and documented the same prognosis for subungual lesions as for cutaneous lesions of equivalent Breslow depth at other sites.3
Nail loss occurs in many patients with subungual melanoma. This spontaneous lift-off of the nail plate has sometimes been erroneously attributed to trauma but failure to regenerate a new nail and non-healing ulceration should raise the index of suspicion of a malignant lesion. Other significant clinical features are pigmentation that extends proximal to the nail fold (Hutchinson’s sign) and de novo pigmentation of the nail that does not migrate distally with growth.8
Figure 2a: High power view showing polygonal Figure 2b: The diagnosis is confirmed by
cells, pleomrphism and nuclear morphology typical HMB-45 staining x 300
of melanoma
Two previous examples of amelanotic melanoma presenting as pyogenic granuloma have been reported.2,9 In one, a teenage girl presented with a small, bright red papule on the scalp that bled easily when injured by hair combing. Elmets and Ceilley (1980) reported a 62 year old man with an ulcerated reddishgrey nodule on the great toe, the true nature of which was not initially suspected because the original resection specimen - thought to be a typical pyogenic granuloma - was not sent for histological examination.2
Amelanotic melanoma usually presents as a vascular tumour or as an ulcerated nodule which fails to heal. Differential diagnosis usually includes haemangioma, superficial haemorrhage, fungal infection or pyogenic granuloma. However, the surface of amelanotic melanomas tends to have a dull red hue,whereas most vascular tumours have a bright red colouration. These tumours bleed less than haemangiomas or pyogenic granulomas, although they tend to ooze a sero-sanguinous fluid as in the case reported here. Amelanotic melanomas are indolent and increase slowly in size over a period of months, unlike pyogenic granulomas which grow rapidly achieving a maximum size within weeks.10
Because of its atypical appearance which often leads to diagnostic delay, amelanotic melanoma has a poor prognosis. The treatment of amelanotic melanoma and pyogenic granuloma differs dramatically and diagnostic delay alters the prognosis for any patient with melanoma. This case, once again, illustrates the importance of routine histological examination of all resected specimens in hand surgery.
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Copyright: 22 April 2002
Correspondence : P. Harrington, 119 Castle Road, Cottingham, East Yorkshire, HU16 5JF
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invites applications for examinerships for the Intercollegiate Diploma in Intensive Care Medicine in the academic year 2002-2003. Applicants must be practising consultants (or academic equivalent) with a substantial commitment to intensive care. Application forms and further details may be obtained from:
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