Folliculosebaceous Poromas With PAK2 and PAK3 Rearrangements: A Report of Two Cases and Review of the Literature

ABSTRACT We report two cases of folliculosebaceous poroma (holocrine poroma) harboring gene rearrangements involving members of the p21‐activated kinase ( PAK ) family. Both tumors were composed of small poroid cells with ductal and sebaceous differentiation and demonstrated strong nuclear GATA3 expression on immunostaining. In one case, fluorescence in situ hybridization (FISH) demonstrated a PAK2 rearrangement; in the other, a PAK3 rearrangement was identified. Although GATA3 has been proposed as a useful marker to distinguish clonal seborrheic keratosis from hidroacanthoma simplex, its strong expression in PAK2/PAK3 ‐rearranged folliculosebaceous poromas suggests limited specificity in this differential context. Notably, to our knowledge, this represents the first reported case of a benign poroma harboring a PAK3 rearrangement. These findings support a role for PAK gene fusions that may contribute to sebaceous differentiation in folliculosebaceous poroma and underscore the molecular heterogeneity of poromas.