Primary cutaneous melanoma arising de novo does occur in prepubescent children, even those who are younger than one year of age. The neoplasm usually is very thick at the time of biopsy, an indication that it grows very rapidly, an inference that is strengthened by the presence of many mitotic figures, some of them discernible in the lower part of the neoplasm, even at the base of it. Hardly ever is the diagnosis of melanoma in a child 10 years of age or younger suspected clinically. At scanning magnification, the silhouette of each of the melanomas in our series is distinctive, different from melanoma seen usually in postpubescents, the chief attributes of it being vertical orientation, diffuse infiltration throughout the dermis, and involvement, often extensively, of the subcutaneous fat (Table 6). A melanoma that occurs in a child may be confused easily histopathologically with a Spitz's nevus, particularly when biopsy of it is superficial and a specimen is small and/or thin. A competent, reflective histopathologist is reluctant to make a diagnosis of melanoma in a child; the odds are that a vertically-oriented melanocytic neoplasm in a child that is vexing histopathologically is a Spitz's nevus rather than a melanoma, but diagnosis is not governed by odds—it is determined by criteria that work. The difficulty in diagnosis is compounded if only the upper part of the lesion is sampled by biopsy; it may be impossible in that circumstance to distinguish with surety between those two neoplasms of such different biologic natures. It is the uppermost part of a melanoma in a child that most closely resembles a Spitz's nevus histopathologically, a pitfall that must be borne firmly in mind if egregious errors are to be avoided. Findings that enable a correct diagnosis of melanoma in a child usually reside below the uppermost part of the neoplasm.

By applying criteria established for differentiation histopathologically of melanoma from Spitz's nevi, an accurate diagnosis of melanoma in a child can be made. It cannot be emphasized too strongly, however, that a diagnosis of melanoma never should be changed to Spitz's nevus simply because of the age of a patient. In the ultimate analysis, diagnosis of melanoma, whether in a child or in an adult, is predicated on morphologic findings and not on age.

Melanomas in prepubescent children grow much more rapidly as a rule than melanomas in adults, but they behave biologically like melanomas in adults in the sense that they have capability to generate widespread metastases and to result eventually in death. Equally important for a histopathologist is to eschew scrupulously a prefix to a diagnosis of Spitz's nevus, like "atypical" and "malignant." Those prefixes serve only to obscure and confuse. Moreover, several of the melanomas in prepubescent children in our series, all of which metastasized, were diagnosed erroneously as "atypical Spitz's nevus," and several others as Spitz's nevus, unmodified.