Figure 2 Histopathological findings of ACC (H&E staining, original magnification ×100). Skin biopsy from the edge of the truncal lesion demonstrating characteristic features of ACC. A) Necrotic surface debris with complete epidermal absence – no identifiable stratum corneum, stratum granulosum, stratum spinosum, or basal layer. The basement membrane is absent, representing full-thickness epidermal loss characteristic of congenital skin aplasia. B) Severely disorganized superficial dermis showing complete loss of normal lamellar architecture. Collagen fibers demonstrate a haphazard, chaotic arrangement without the typical parallel orientation seen in healthy reticular dermis. The papillary-reticular dermal junction is completely obliterated with marked hypocellularity. C) Dense eosinophilic collagen bundles with irregular, wavy orientation, lacking the normal basket-weave pattern of physiologic dermis. This abnormal collagen architecture represents pathological fibrosis from intrauterine wound healing rather than normal dermal remodeling. D) Zone of increased fibroblast proliferation at the interface between preserved deeper dermis and damaged superficial tissue, with spindle-shaped nuclei oriented multidirectionally, indicating active reparative response to embryonic injury. E) Patchy chronic inflammatory infiltrate consisting predominantly of lymphocytes and macrophages distributed throughout the dermis without granuloma formation. F) Complete absence of pilosebaceous units, eccrine glands, and apocrine glands throughout the examined field, confirming full-thickness dermal involvement and congenital etiology, as these structures cannot regenerate after embryonic destruction. These findings establish the diagnosis of Type V ACC. ACC – aplasia cutis congenita; H&E – hematoxylin and eosin.