title: Histological characterization of regression in acquired immunodeficiency syndrome-related Kaposi's sarcoma.
abstract: BACKGROUND
  Kaposi's sarcoma (KS) is an angioproliferative lesion that may regress or progress. Progression is related to spindle cell proliferation and the expression of human herpes virus-8 latency genes, including latent nuclear antigen-1 (LNA-1), cyclin-D1, and bcl-2. KS regression has not been well characterized histologically. Therefore, this study was undertaken to characterize the histopathology of pharmacologically induced regressed cutaneous KS.
  
  
  METHODS
  Skin punch biopsies from eight patients with acquired immunodeficiency syndrome (AIDS)-related KS, that regressed following chemotherapy with paclitaxel or the angiogenesis inhibitor Col-3, were investigated by light microscopy. Comparative immunophenotyping on pre- and post-treatment specimens for CD31, LNA-1, cyclin-D1, bcl-2, and CD117 (c-kit) was performed.
  
  
  RESULTS
  Clinical and histologic features of regression were similar for paclitaxel and Col-3 treatment. On clinical examination, lesions flattened, became smaller, and lost their purple-red appearance, resulting in an orange-brown macule. Histological regression was divided into partial (n = 3) and complete (n = 5) regression. Partially regressed lesions had a significant reduction of spindle cells in the dermal interstitium, with residual spindle cells arranged around superficial and mid-dermal capillaries. Complete regression was characterized by an absence of detectable spindle cells, with a slight increase in capillaries of the superficial plexus. All regressed samples exhibited a prominent, superficial, perivascular, lymphocytic infiltrate and abundant dermal hemosiderin-laden macrophages. This clinicopathologic picture resembled the findings of pigmented purpura. CD31 staining correlated with the reduction of spindle cells. Regression was accompanied by a quantitative and qualitative decrease in LNA-1 and cyclin-D1 immunoreactivity, but no change in bcl-2 or c-kit expression.
  
  
  CONCLUSIONS
  Pharmacologically induced regression of AIDS-related cutaneous KS is characterized by a complete loss or decrease of spindle cells, increased lymphocytes, and prominent dermal siderophage deposition. Without any prior knowledge of the history of KS regression following therapy, regressed KS lesions may be misdiagnosed clinically and histologically as pigmented purpuric dermatitis.
authors.affiliation: Department of Pathology, Beth Israel Deaconess Medical Center, and Department of Pathology, 330 Brookline Avenue, Boston, MA 02215, USA. lpantano@caregroup.harvard.edu
authors.forename: Liron
authors.initials: L
authors.lastname: Pantanowitz
authors.forename: Bruce J
authors.initials: BJ
authors.lastname: Dezube
authors.forename: Geraldine S
authors.initials: GS
authors.lastname: Pinkus
authors.forename: Steven R
authors.initials: SR
authors.lastname: Tahan
mesh_terms: D000163:Acquired Immunodeficiency Syndrome / Q000150:complications / Q000473:pathology*; D000328:Adult; D000972:Antineoplastic Agents, Phytogenic / Q000627:therapeutic use; D014408:Biomarkers, Tumor / Q000032:analysis; D003872:Dermatitis / Q000175:diagnosis; D003937:Diagnosis, Differential; D006801:Humans; D007124:Immunoenzyme Techniques; D016130:Immunophenotyping; D008297:Male; D008875:Middle Aged; D017239:Paclitaxel / Q000627:therapeutic use; D010859:Pigmentation Disorders / Q000175:diagnosis; D011693:Purpura / Q000175:diagnosis; D012074:Remission Induction; D012514:Sarcoma, Kaposi / Q000188:drug therapy / Q000209:etiology / Q000473:pathology*; D012878:Skin Neoplasms / Q000188:drug therapy / Q000209:etiology / Q000473:pathology*; D013754:Tetracyclines / Q000627:therapeutic use
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D014408:Biomarkers, Tumor; D013754:Tetracyclines; C117155:tetracycline CMT-3; D017239:Paclitaxel