title: "Pseudoneoplastic" leprosy. Leprosy revisited.
abstract: A 70-year-old Italian man with a history of squamous cell carcinoma of the lung presented with a nodular skin eruption. He had traveled extensively in India and Sri Lanka. The nodules were well demarcated and measured up to 3.5 cm in diameter. Histologically, there was a proliferation of spindled and polygonal cells with focal and relatively inconspicuous cytoplasmic vacuolation. A macrophage-monocyte lineage for the cells was confirmed by paraffin section immunohistochemistry, using the monoclonal antibodies anti-CD45, MAC-387, KP-1, UCHL-1, MT-1, L26, and MB2. Infiltrating borders, extension of the lesion into the subcutis, and involvement of small dermal nerves and eccrine glands initially suggested the possibility of a "histiocytic" neoplasm of indeterminate biological potential. However, air-dried and Giemsa-stained material from a fine-needle aspirate of one cutaneous nodule showed needle-shaped intracellular "negative images," and acid-fast stains revealed a large number of intracytoplasmic bacilli in virtually all of the vacuolated lesional cells. Furthermore, a second skin nodule that was excised 3 weeks after initial presentation showed the typical morphology of lepromatous leprosy. The clinicopathologic features of this case demonstrated several similarities with those of so-called "histoid" leprosy. Unusual morphologic variants of leprosy need to be considered in the interpretation of unusual "histiocytic" infiltrates in order to avoid a mistaken diagnosis of neoplasia, regardless of the geographic locale in which the patient is evaluated.
authors.affiliation: Section of Dermatopathology, Lauren V. Ackerman Laboratory of Surgical Pathology, Washington University Medical Center, St. Louis, Missouri, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Triscott
authors.forename: O
authors.initials: O
authors.lastname: Nappi
authors.forename: G
authors.initials: G
authors.lastname: Ferrara
authors.forename: M R
authors.initials: MR
authors.lastname: Wick
mesh_terms: D000368:Aged; D001707:Biopsy, Needle; D002294:Carcinoma, Squamous Cell / Q000532:radiotherapy / Q000556:secondary; D003937:Diagnosis, Differential; D004439:Eccrine Glands / Q000473:pathology; D015620:Histiocytic Disorders, Malignant / Q000175:diagnosis* / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D015440:Leprosy, Lepromatous / Q000175:diagnosis* / Q000473:pathology; D008175:Lung Neoplasms / Q000532:radiotherapy; D008297:Male; D012867:Skin / Q000294:innervation / Q000473:pathology; D012878:Skin Neoplasms / Q000175:diagnosis* / Q000473:pathology