Braunberger TL, Adelman M, Shwayder TA, Clarke LE, and Friedman BJ. 26856 Proliferative nodule resembling angiomatoid Spitz with pronounced degenerative atypia arising within a giant congenital nevus. J Am Acad Dermatol 2021; 85(3):AB118.
J Am Acad Dermatol
Proliferative nodules arising within congenital melanocytic nevi present a diagnostic challenge for dematopathologists given their close resemblance to melanoma. In difficult cases, ancillary molecular tests can be used to better exclude the possibility of malignancy. We report case of a biopsy and subsequent excision of an unusual proliferative nodule with overlapping features of angiomatoid Spitz tumor and ancient melanocytic nevus which demonstrated normal findings on both chromosomal microarray and a gene expression profiling assay. Our case is noteworthy given its striking resemblance to what has been reported for an angiomatoid Spitz tumor. To our knowledge, this particular morphologic subset of Spitz has been described primarily in the context of spontaneous melanocytic tumors arising de novo outside the context of a congenital lesion. The pathology showed bizarre cytological features along with a myxoid and highly vascularized stroma which is thought to represent degenerative atypia characteristic of an “ancient nevus.” The lesions described as ancient nevi have some overlapping stromal features with angiomatoid Spitz tumors. A low proliferation index and paucity of mitotic figures is characteristic of these neoplasms. We hypothesize that continued host response to the lesion may be responsible for inducing the observed cytological and stromal derangement. Interestingly, these changes increased from the time of biopsy to the excision. Future studies should aim to define the genetic and immunologic signature of these lesions to help predict prognosis. The relationship between angiomatoid Spitz tumor, ancient change, and regressing nevi should also be investigated.