Authors: Shaymaa Hegazy MD, Rana Naous MD
Case Presentation
A male in his mid-forties with no significant medical history presented with a 2.5 cm left arm lesion which was growing in size over a few months. A skin excision was performed. A 1.5 cm tan white glistening well-circumscribed lesion was identified on the cut sectioning.
Histopathologic features
Histologic examination demonstrates a dermal well-circumscribed lesion composed of spindle to ovoid cells. The tumor cells showed mild nuclear atypia with vesicular chromatin and small nucleoli (Figure 1A). The tumor cells are arranged in whorls and fascicles, embedded in a richly vascular myxoid stroma (Figure 1B). The mitotic activity reached up to 1 per 10 high power fields and necrosis was absent.
Immunohistochemical Studies
Immunohistochemical stains demonstrated the tumor cells were diffusely positive for CD34 and ALK-1(Figures 2A and 2B), and patchy positive for S100 ( Figure 2C) and SMA while were negative for SOX-10, HMB45, Melan-A, desmin, myogenin, STAT6, TLE1, AE1/AE3, ERG, and MUC4. H3K27me3 stain is retained.
Fluorescence in situ hybridization (FISH) studies
FISH studies for ALK gene rearrangement were performed and were positive.