Plexiform Atypical Spitz Tumor With Rosette-Like Giant Cells: A Histologic and Immunohistochemical Study on a Case Suggesting Ganglioneuroblastic Differentiation: Review of the Literature and Considerations on Histogenesis

Rosette-like formations in melanocytic neoplasms: A case report and literature review

Homer-Wright-like rosettes are a common finding in neural tumors but seldom seen in melanocytic nevi and melanoma. We report a case of a 23-year-old male with a compound melanocytic nevus with such rosette-like structures and summarize the current literature on this histopathological feature in melanocytic neoplasms. A symmetric, well-circumscribed, compound nevus consisting of aggregations of epithelioid melanocytes with eccentric nuclei and central eosinophilic cytoplasm, resembling Homer-Wright rosettes, was present on biopsy. Immunohistochemical stains strongly supported a melanocytic entity and were negative for NTRK1/2/3, a fusion protein potentially associated with rosette-like structures. We found 17 other cases of benign melanocytic nevi, including 9 atypical Spitz tumors and 6 Spitz nevi, and 11 malignant melanomas, including 3 Spitz melanomas and 4 metastases. We observed remarkable diversity among lesion morphologies containing rosettes, as well as level of prominence and cytology of the rosettes themselves. This case illustrates the morphologic malleability of neural-crest-derived lesions to share microscopic and phenotypic attributes.

Effect of stress-induced polyploidy on melanoma reprogramming and therapy resistance

Melanomas and their precursors, the melanocytes, are frequently exposed to UV due to their anatomic location, leading to DNA damage and reactive oxygen stress related harm. Such damage can result in multinucleation or polyploidy, in particularly in presence of mitotic or cell division failure. As a consequence, the cell encounters either of two fates: mitotic catastrophe, resulting in cell death, or survival and recovery, the latter occurring less frequently. However, when cells manage to recover in an polyploid state, they have often acquired new features, which allow them to tolerate and adapt to oncogene- or therapy induced stress. This review focuses on polyploidy inducers in melanoma and their effects on transcriptional reprogramming and phenotypic adaptation as well as the relevance of polyploid melanoma cells for therapy resistance.

ALK-positive compound Spitz nevus with extensive perineural and intraneural neurotropism

Historically recognized by their characteristic histopathologic features, Spitz neoplasms are now known to be molecularly defined by mutually exclusive recurrent abnormalities that cause activation of the MAPK pathway. Spitz neoplasms with ALK rearrangements frequently demonstrate polypoid growth with a plexiform arrangement of nested, fusiform melanocytes in intersecting fascicles. Although neurotropism has been described in indolent Spitz neoplasms, this feature is not frequently mentioned in publications on histopathologic assessment of this group of melanocytic tumors. Here, we present an unusual case of a 3-year-old female with an ALK-positive compound Spitz nevus with extensive perineural and intraneural neurotropism occurring on the vermilion border of the lower lip.

Central nervous system ganglioneuroblastoma harboring MYO5A-NTRK3 fusion

Central nervous system (CNS) ganglioneuroblastoma is a rare neuroectodermal neoplasm and little is known about its clinical and biological features. Herein, we report a pediatric case of CNS ganglioneuroblastoma harboring MYO5A-NTRK3 fusion. The patient, a 4-year-old boy, underwent a partial resection of a supratentorial tumor that was histopathologically diagnosed as a CNS ganglioneuroblastoma. Treatment with radiotherapy was started per the St Jude Medulloblastoma 03 (SJMB03) protocol; however, the tumor progressed rapidly and radiotherapy was temporally discontinued. Meanwhile, the patient underwent a second surgery, in which a gross total resection was successfully performed, following which he completed the remaining protocol-based therapy. Although an early focal recurrence was detected for which he received additional radiotherapy and oral temozolomide, the patient remained in complete remission for 14 months after the completion of the treatment. A central pathological review and molecular analysis were performed that revealed a MYO5A-NTRK3 fusion. Interestingly, the MYO5A-NTRK3 fusion has been recurrently detected in melanocytic tumors but not in other types of tumors. Therefore, it can be speculated that our case might partly share tumorigenesis mechanisms with MYO5A-NTRK3-positive melanocytic tumors. In addition, our case may enable an improved understanding of the pathogenesis and clinical features of CNS ganglioneuroblastomas.