Nodular lesions arising in a large congenital melanocytic naevus in a newborn with eruptive disseminated Spitz naevi

Abstract

Congenital malignant melanoma within a pre-existing large congenital melanocytic naevus (CMN) is exceedingly rare. Its incidence is difficult to determine due to the small number of reported cases and because of problems associated with diagnosis. Some benign nodular proliferations (called proliferative nodules) arising in CMN, while rare, are significantly more common and can mimic malignant melanoma clinically or histologically. There are no reported cases of congenital melanoma or benign proliferative nodules in CMN in patients who also had eruptive disseminated Spitz naevi. We describe a girl who was noted to have a dark-brown plaque with several large erythematous nodules affecting the scalp at delivery, in addition to multiple erythematous dome-shaped papules that developed in a disseminated manner over several months, beginning at 10 days of age. It was difficult, not only clinically but also histologically, to determine the benign or malignant nature of all of these lesions. As primary cutaneous melanoma, atypical proliferative nodules in CMN, bland CMN or CMN with foci of increased cellularity and Spitz naevi show clear differences in the genetic aberration patterns, comparative genomic hybridization (CGH) could be a diagnostic help in ambiguous cases such as this. CGH performed on this patient showed multiple DNA copy number changes in the most atypical nodule, but such alterations could not be found in the remainder of the lesions. CGH showed differences between the nodular lesions that occurred in the CMN and helped us in supporting the diagnosis of this unique case of benign proliferative nodules and a possible congenital melanoma arising in a large CMN, associated with multiple widespread eruptive Spitz naevi.

Metastatic Melanoma in Association With a Giant Congenital Melanocytic Nevus in an Adult

“…The difficulty in histopathological diagnosis of CMNs arises from the various complex patterns of cellular overgrowth within these lesions. 11 In this article, we describe the case of a 22-year-old patient who presented with a nodule arising within a GCMN and then developed an axillary mass. The controversial histopathologic picture of this case, open to interpretation as BPN or as melanoma, posed a diagnostic challenge.…”

“…2 Immunohistochemistry, molecular tests that investigate DNA copy number alterations such as fluorescence in situ hybridization (FISH) and comparative genomic hybridization (CGH) have limited value in distinguishing BPNs from MM. [3][4][5][6][7][8][9][10][11] CGH has demonstrated marked differences between chromosomal aberration patterns in melanomas and several subsets of melanocytic nevi, and may be a diagnostic tool for histologically equivocal melanocytic tumours. 7,12 We present the case of a 22-year-old woman with a nodule arising in a giant congenital melanocytic nevus (GCMN) with an axillary mass suggesting a subcutaneous and nodal metastasis of melanoma, and discuss the utility of FISH and array CGH technology in the diagnosis of ambiguous melanocytic proliferations arising within CMN.…”

Mass Spectrometry Imaging Can Distinguish on a Proteomic Level Between Proliferative Nodules Within a Benign Congenital Nevus and Malignant Melanoma

“…Proliferative nodules show a wide spectrum of changes including findings sometimes overlapping with those found in malignant melanoma. (17, 18)…”

“…(14, 15, 18, 19) On the other hand, nodules with two or more of the following histopathological features are considered atypical: sharp demarcation, expansive growth, epidermal effacement, focal pagetoid spread, variable pleomorphism, one or more mitotic figures per high power field, and atypical mitoses. (15, 20) Malignant melanoma should be suspected when there are large zones of necrosis, extremely atypical melanocytes, and numerous mitoses.…”

Proliferative nodule in melanocytic nevi mimicking deep penetrating nevus

“…However, it is important to keep in mind that in a small subset of cases, benign PNs can be large, highly cellular and may have atypical melanocytes, mitoses, zones of necrosis and even ulceration. 6 …”