Micromelanomas: A Review of Melanomas ≤2？mm and a Case Report

The ABCD acronym used to screen pigmented lesions for melanoma obviously was not designed to contend with melanomas that are under 2？mm in diameter. Previously, views ranged that such small lesions could not be melanomas until a few reports of such “micromelanomas” emerged. The author presents a 2？mm melanoma in situ presenting as an insignificant pigmented lesion in a 60-year-old patient with no previous history of melanoma or multiple nevi—which is usually the norm in cases of small melanoma. This paper reiterates the fact that when it comes to a melanoma, size does not matter. In this paper, the term “micromelanoma” is used by the author to represent melanomas under 2？mm. Dermatoscopy and histopathology findings are discussed in this case, along with a review of small melanomas. 1. Background In 1985, the oft-quoted ABCD acronym was developed for melanoma screening as a public health tool to aid the diagnosis of melanomas [1]. Asymmetry, border, color, and diameter of the pigmented lesion were parameters discussed in this context. In 1987, Schmoeckel and Braun-Falco even suggested that pigmented lesions under 5？mm cannot be considered melanomas as clinical and histological features only became apparent when lesions enlarged beyond 5？mm size [2]. Then a study from the Sydney Melanoma Unit undertook a large retrospective study and concluded that 31.1% of lesions were 6？mm or less in diameter [3]. After adjusting for tissue shrinkage among specimens from this Australian cohort, it was reported that only 10% of invasive melanomas were small-diameter tumors [4]. A few years later, a paper presented a series of invasive small-diameter melanomas, debating if the “D” should be removed from the ABCD acronym [4]. Recently, a case report reviewed the dermatoscopy and dermatopathology findings of a tiny invasive melanoma in a 38-year-old patient who had >100 nevi—with the smallest diameter ever of a reported melanoma of 1.6？mm [5]. Some groups reported that small-diameter melanoma tumor thicknesses ranged from 0.11 to 1.5？mm, with a median thickness of approximately 0.7？mm [6]. The author presents a 2？mm melanoma in situ presenting as a solitary de novo lesion in a 60-year-old patient with no previous history of melanoma or multiple nevi—illustrating the fact that when it comes to a melanoma, established clinical patterns or size do not seem to matter. As many authors have already stated, the ABCD criteria often does not seem to matter [7, 8]. In this paper, the term “micromelanoma” is coined to represent melanomas under 2？mm. The presentation is also unusual