S4C7P1-3: the elongated rete ridges qualify as hyperplasia of the basal unit of the epidermis; it is this quality which also is responsible for the psoriasiform features. Wavy, thin cells appear as naked nuclei among the keratinocytes of the elongated rete ridges. These distinctive cells are migratory histiocytes. The prominence of such cells in epidermal infiltrates is a characteristic feature of lesions of secondary lues. This lesion is also characterized by a high component of plasma cells in the dermal infiltrates (area outlined by blue arrows). The plasmacytosis of secondary lues is variable in degree from lesion to lesion.

S4C7P1-4: some of the migratory histiocytes in the epidermis, and the dermis can be identified near blue arrows. The green arrows point to some of the plasma cells. Inter-cellular spaces of the epidermis are widened (spongiosis). The papillary dermis (to the left) is edematous. A loose cluster of plasma cells (green arrows) is represented.

S4C7P1-5: In this example, the lichenoid qualities are more prominent; some of the partially preserved rete ridges have pointed extremities; the rete ridges have been partially eroded by a lichenoid process. The prominent lichenoid qualities (particularly the band-like infiltrates) in combination with the perivenular infiltrates in the dermis qualify the overall pattern as a “ lichenoid lymphocytic vasculitis.” The perivenular component is in sharp contrast to the relative absence of such a component in lesions of classic lichen planus (secondary lues).

S4C7P1-6: In combination, the lichenoid and psoriasiform qualities of this lesion of secondary lues provide pityriasic qualities. The patterns are distinguished from those of a lesion of pityriasis lichenoides by the presence of plasma cells in the dermal infiltrates. The rich infiltrate of histiocytes does not provide distinctions between lesions of secondary lues and pityriasis lichenoides; both tend to be rich in histiocytes. On the other hand, granulomatous components in a problematic lesion showing pityriasic qualities would be a feature in favor of secondary lues.