Cutaneous melanoma of such massive size is rarely seen in developed, industrialised countries, especially with the success of current public screening and prevention programmes. A review of the recent literature demonstrates isolated case reports which describe patients who present with giant melanomas of various anatomic sites, including the back,1,2
To our knowledge, patient B—who had a 19 cm diameter lesion—represents the largest primary melanoma of the upper extremity and one of the largest melanomas of all reported to date.
Based on size alone, the current TNM staging system for melanoma designates our two patients’ tumours as T4, which in actuality includes all lesions with a thickness >4 mm (not cm). Lymph node status has been shown in two large series of T4 melanomas to be the most important prognostic indicator for survival.7,8
Five year survival rates differ by almost twofold in node negative versus node positive patients. Independent of lymph node status, prognosis in T4 melanomas also depends on several other factors including absolute thickness, ulceration, and vascular involvement.Regardless of size, melanomas that are polypoid or exophytic are associated with increased malignant potential and overall, worse prognosis.9–11
These tumours demonstrate a nodular growth pattern and often are thicker and ulcerated at the time of presentation. Five year survival rates in small case series range from 33–42%. A case report of a patient with a preauricular polypoid melanoma describes local and regional recurrence <1 month after surgical excision.12
Despite the extremely large size of the melanomas in our two patients, what is remarkable is that although both patients had regional lymphadenopathy, neither had evidence of distant metastases at initial presentation. This pattern of local spread without distant disease in such massive melanomas was also noted in several other case reports1,4,5
found on review of the literature. Conventional sized melanomas are thought to follow a paradigm of orderly disease progression from primary site to regional lymph nodes and subsequently to distant sites.13–15
It is interesting that even at such enormous sizes, these melanomas still appear to follow this paradigm.
Equally intriguing is the rapid development of metastases after primary tumour resection, seen in both our patients. Primary tumour induction of tumour dormancy at distant sites has been observed in animal models and multiple tumour types.16,17
Although still controversial, the mechanism for this phenomenon may be related to production of circulating angiogenesis inhibitors by the primary tumour.18,19
In addition, host immune cells at the tumour site may help maintain a state of equilibrium between slowly proliferating tumour cells and those undergoing apoptosis.20,21
In our two patients, it is likely that distant microscopic metastases, not visible on conventional imaging, were already present at initial presentation. We hypothesise that primary tumour resection may have removed the source of endogenous inhibitory factors or somehow altered immune surveillance mechanisms to allow for outgrowth of distant metastases. Further investigation with a larger cohort of patients would be needed to make any firm conclusions.
Given the rarity of giant melanomas, it is also difficult to draw conclusions as to an appropriate management strategy. We and others1,2,4–6
support an attempt at cure with multimodality treatment, including aggressive surgical resection. Even if cure is not achieved, palliative debulking may at least offer symptom control (for example, local infection and bleeding). As giant melanomas have several poor prognostic factors (size, exophytic growth, ulceration, nodal disease), consideration should also be given to experimental treatment regimens and novel therapeutic agents.
- Melanomas can present, in rare circumstances, as giant, multi-centimetre tumours.
- Giant melanomas appear to follow orderly progression first to lymph nodes, then distant sites.
- Aggressive multimodality treatment should be offered to patients, but efficacy of this approach is inconclusive due to rarity of these melanomas.