c18t3P1: This compound giant congenital nevus shows mild immaturity; the pattern of collagen bundles in the lower 1/2 of the dermis is relatively well-formed. Immaturity may have some significance in regard to the development of areas of “atypical nodular hyperplasia,” and even melanoblastoma of infancy. Lentiginous and junctional changes are mild and spotty. There is some degree of dysplasia of dermal type in the population of cells in the papillary dermis, and at the interface between the papillary dermis and the reticular dermis. The rounded nests of cells in the deeper portion of the cellular component might be characterized as inverted type A pattern. The atypia in the dermal component near the dermal-epidermal interface is a common finding in giant congenital nevi, particularly in lesions showing some degree of immaturity. The degree of cellularity at the interface between the papillary dermis and the reticular dermis is also a measure of immaturity.
c18t3P2: This is another example of giant congenital nevus showing immaturity of the component in the reticular dermis. The lesion is cellular throughout the reticular dermis and the less cellular areas show pallor and a reduction in the size of collagen bundles (moderate to moderately severe immaturity).
c18t3P3: The cellular component in this field of a giant congenital nevus is plaque-like and might be characterized as a variant of atypical “nodular” hyperplasia. The nevus cells have scanty cytoplasm. The nuclei are uniform, but many of the nuclei have open chromatin patterns with “heavy” nuclear membranes.
c18t3P4: In this field from a giant congenital nevus, there are no lentiginous and junctional components; the lesion is dermal in the reticular dermis. The lesion is somewhat polypoid; it might be characterized as showing atypical nodular hyperplasia. From a different perspective, this is marked immaturity; the lesion has “blastoid” qualities, but this is not a melanoblastoma of infancy. The collagenous framework of the reticular dermis has not differentiated in this population of immature cells.
c18t3P5: This is the region of mid-reticular dermis but there is a poorly developed fibrous framework; There is marked immaturity. Nuclei show margination of chromatin with heavy nuclear membranes.
c18t3P6: This is another example of “blastoid” immaturity in the reticular dermis in a giant congenital nevus. There is some evidence of differentiation in the lower 1/2 of the field.
