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c19t3P1:This is a giant congenital nevus. It is immature in pan-dermal patterns. Primitive small cells form a plaque near the dermal-epidermal interface; the lesion is apparently a dermal type dysplasia; there are no lentiginous and junctional components. A column of closely aggregated cells extend from the plaque into the dermis along the axis of a follicle. On the basis of patterns, it might be proposed that the primitive cells are precursors of cells destined for the adventitial dermis but due to derangements in organization and maturation, have not been incorporated into the mesenchyme. In this approach, the development of the dermis is influenced by neurocristic migrants; in this dysplasia, there is delayed incorporation of the neurocristic cells into the mesenchyme; the cells proliferate to form a dysplastic pattern of blastoid type; there is also a potential to evolve into a true blastoma (melanoblastoma of infancy). The patterns are somewhat nodular along the surface.
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c19t3P2: The dysplasia is pan-dermal and extends in septal patterns into the fat. There is a transition from cellular areas to pale, less cellular areas. Even in the pale areas, the collagenous framework of the reticular dermis is poorly developed (marked immaturity).
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c19t3P3: In the cellular areas, the cells are small and dark; they have uniform nuclear characteristics and scanty cytoplasm. In this field, there is no definition of a follicular sheath.
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c19t3P4: The cytologic features are monotonous. Chromatin is marginated and nuclear membranes tend to be “heavy.” There is scanty interstitial matrix.
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c19t3P5: At high magnification, the nuclear features are uniform. Some of the nuclei are notched or grooved. There are scattered deposits of pigment. Focally, some of the cells are spindle shaped.
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c19t3P6: At the transition from cellular to pale zones, the interface is poorly defined. The cells of the pale areas are basically similar to those of the cellular areas; they simply are more widely spaced in a delicate fibrous matrix; there is partial maturation in the pale areas. This lesion was associated with a small parenchymal deposit of tumor in a regional lymph node.
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c19t3P7: I believe this was a small lesion separate from the large lesion of the preceding illustrations. In any case, the plaque-like area in the upper portion of the dermis is not as wide and is more loosely cellular. The cellular areas also are represented in peri-follicular arrays. In the lower 2/3’s of the dermis, cellular areas are less prominent and tend to be peri-vascular in distribution. The fibrous mat of the reticular dermis is better defined; the lesion shows partial maturation. In this approach, the degree of cellularity in a lesion of this type is a measure of maturation; cellular lesions with poorly developed fibrous frameworks are immature.
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