S11C10P5-1: Borderline tuberculoid leprosy with columns of epithelioid histiocytes. Lymphocytes are few in number, and loosely spaced.

S11C10P5-3: Same lesion as P11-5-2 showing an involved nerve in the subcutaneous fat. The infiltrate involves both the perineurium and the endoneurial space. There is edema of the endoneurial space.

S11C10P5-4: Same lesion as P11-5-2 & 3, showing scattered histiocytes with several organisms in their cytoplasm. A red arrow identifies one such cell.

S11C10P5-5: The classic pattern of a cutaneous suppurative granuloma is represented. The irregular, red area is a zone of hemorrhage  and suppuration. It is partially outlined by hyperplastic squamous epithelium (blue arrows). At this level and in the reticular dermis in this pattern, the epithelium is cytologically bland but invasive.The epithelium partially outlining the area of suppuration represents pseudoepitheliomatous hyperplasia; it is present in invasive patterns at a level well beyond the bounds of the adventitial dermis (i.e., the stroma for squamous epithelium of the dermis). Epithelium, sitting among collagen bundles of the reticular dermis, is abnormal; such a relationship can only be obtained by an extension of the epithelium into the reticular dermis in isolated nests, or in continuity with preexisting structures (invasion). There is an adjacent zone of granulation tissue containing granulomas. A suppurative granuloma is most often a feature of an infectious process, such as a mycobacterial or deep fungus infection. This lesion represents the response to an infection with atypical acid fast organisms.

lS11C10P5-6: The epidermis shows acanthosis and effacement of rete ridges. The ostium of a follicle contains a plug of concentrically laminated, keratinized debris. A lesion is centered in the dermis beneath the ostium of the follicle. It is expansile (tumorous); it is necrotic centrally. Ghost outlines of cells are not preserved in the area of necrosis. Histiocytes and occasional giant cells are arranged in palisades at the periphery of the zone of necrosis. The histiocytic nature of the lesion and the tumoral qualities combine to make this lesion a “granuloma.” Although there is palisading of histiocytes at the periphery of the zone of necrosis, this is not the palisaded granuloma of granuloma annulare. The relationships suggest that the lesion might be perifollicular in orientation; the features are compatible with those of lupus milaris disseminatus faceii. Although at one time considered to be a tuberculid, this lesion is currently accepted as a variant of acne.