The eye of the tiger: Case report of a featureless invasive melanoma disguised within a tattoo with implications for clinical practice (R1)

We present the case of a 59-year-old Australian man with an invasive melanoma within a decorative tattoo of a tiger. The only morphologic clues to malignancy which were present could alternatively be explained by tattoo pigment. The patient has provided written consent for publication of this case report. The patient with Fitzpatrick skin type II, and a naevus count exceeding 50, presented to his general practitioner for his first skin cancer examination. A lesion noted on his chest was nestled within the blue pigment of a tattoo (Figure 1a). The tattoo had been present for more than a decade, the patient being unable to recall when the skin lesion had first appeared, whether prior to the tattoo or subsequently. A discussion with the patient ensued about the possibility of missing a melanoma, given that the tattoo pigment could mimic and/or mask dermatoscopic clues like blue/grey colours. Options of excision biopsy and serial dermatoscopic digital imaging were presented, along with the information that asymmetrical blue colour, due to endogenous melanin, is a clue to invasive malignancy in the context of melanoma.1 The patient elected to proceed with excisional biopsy which discovered an invasive superficial spreading melanoma, Clark level 2, Breslow thickness 0.29 millimetres (Figure 2). While evidence that tattooing can cause melanoma is not strong,2 with one in four Australians reported to be carrying tattoos,3 this case adds weight to existing evidence that tattoo pigment can compromise clinical and dermatoscopic assessment of skin lesions.4 The skin lesion being assessed was 6 mm in diameter in its greatest dimension, with a single dermatoscopic pattern, lines reticular and a uniformly gradual, well-demarcated border (Figure 1b). Blue colour was present on one half of the otherwise brown lesion, corresponding to a band of underlying tattoo pigment (Figure 1b). While the tattoo pigment could reasonably be regarded as causing the blue colour within the footprint of the lesion, asymmetric blue colour due to melanin is a known clue to invasive melanoma.1 In this case, the decision taken by the informed patient was fortuitously the correct one, but the alternative decision not to excise would also have been reasonable, which raises the question of how better to evaluate such cases. In response, there is emerging evidence for the use of confocal microscopy, which visualises the epidermis, dermoepidermal junction and papillary dermis, to evaluate for evidence of melanoma at these levels, irrespective of the presence of exogenous pigment in the dermis.5, 6 Another tool which is available to potentially mitigate these difficulties is photographic technology, the use of which is recommended by current Australian guidelines for the evaluation of melanoma in clinical practice.7 We suggest that patients be educated about the value of having an examination of the skin, including dermatoscopic examination of any lesions which are present, and baseline photo documentation, prior to the application of tattoos. Additionally, the advice of Kluger et al., of leaving a free margin around existing moles when tattooing,8 is recommended. None. Raghu Vasanthan provided the clinical case, the clinical images and substantially wrote the paper. Louise Vivien Killen signed out the pathology report, provided the histology images and wrote the dermatopathology content. Cliff Rosendahl contributed to the discussion, prepared image collages, responded to review and edited the final manuscript. The authors declare no conflicts of interest.