ALK-rearranged CD34 positive superficial spindle cell tumour

Anaplastic lymphoma kinase (ALK) rearranged spindle cell mesenchymal tumours are an emerging category of soft tissue neoplasm with variable clinical and pathological features.1–3 We describe a case 6-year-old female who presented pigmented lesion on her abdomen. Biopsy the showed low-grade dermally based prominent storiform architecture, some entrapped collagen focal extension into subcutis. There was no mitosis or anaplasia. On immunohistochemistry, tumour cells were CD34+ ALK+ staining for S100, smooth muscle actin (SMA) epithelial membrane antigen (EMA). RNA sequencing performed biopsy detected 5’ to 3’ in-frame fusion LRRFIP1 exon 17 ALK 20. The findings CD34+/ALK+ bland cutaneous confirmed LRRFIP1-ALK consistent ALK-rearranged superficial (aka myxoid neoplasm). recurrence following complete excision lesion. emphasises importance awareness this evolving entity its unique morphologic, immunophenotypic molecular cytogenetic features potential targeted therapy. References 1. Dermawan JK, Azzato EM, Goldblum JR, Rubin BP, Billings SD, Ko JS. Superficial neoplasm: tumor distinctive morphology profile. Mod Pathol 2021; 34: 1710–1718. 2. DiNapoli SE, Mullaney KA, et al. neoplasms: report 9 cases further expanding clinicopathologic spectrum positive group tumors. Genes Chromosomes Cancer 2023; 62: 75–84. 3. Tan SY, Al-Ibraheemi A, Ahrens WA, rearrangements in infantile fibrosarcoma-like kidney. Histopathology 2022; 80: 698–707.