title: Lymphatic density and metastatic spread in human malignant melanoma.
abstract: Malignant melanoma (MM), the most common cause of skin cancer deaths, metastasises to regional lymph nodes. In animal models of other cancers, lymphatic growth is associated with metastasis. To assess if lymphatic density (LD) was increased in human MM, and its association with metastasis, we measured LD inside and around archival MM samples (MM, n=21), and compared them with normal dermis (n=11), basal cell carcinoma (BCC, n=6) and Merkel cell carcinoma (MCC), a skin tumour thought to metastasise through a vascular route (MCC, n=6). Lymphatic capillary density (mm(-2)), as determined by immunohistochemical staining with the lymphatic specific marker LYVE-1, was significantly increased around MM (10.0+/-2.5 mm(-2)) compared with normal dermis (2.4+/-0.9 mm(-2)), BCC (3.0+/-0.9 mm(-2)) and MCC (2.4+/-1.4 mm(-2)) (P<0.0001). There was a small decrease in LD inside MM (1.1+/-0.7 mm(-2)) compared with normal dermis, but a highly significant decrease in BCC (0.14+/-0.13) and MCC (0.12+/-2.4) (P<0.01 Kruskal-Wallis). Astonishingly, LD discriminated between melanomas that subsequently metastasised (12.8+/-1.6 mm(-2)) and those that did not (5.4+/-1.1 mm(-2), P<0.01, Mann-Whitney). Lymphatic invasion by tumour cells was seen mainly in MM that metastasised (70% compared with 12% not metastasising, P<0.05 Fisher's Exact test). The results show that LD was increased around MMs, and that LD and tumour cell invasion of lymphatics may help to predict metastasis. To this end, a prognostic index was calculated using LD, lymphatic invasion and thickness that clearly discriminated metastatic from nonmetastatic tumours.
authors.affiliation: Department of Physiology, University of Bristol, Preclinical Veterinary School, Southwell Street, Bristol BS2 8EJ, UK.
authors.forename: J D
authors.initials: JD
authors.lastname: Shields
authors.forename: M
authors.initials: M
authors.lastname: Borsetti
authors.forename: H
authors.initials: H
authors.lastname: Rigby
authors.forename: S J
authors.initials: SJ
authors.lastname: Harper
authors.forename: P S
authors.initials: PS
authors.lastname: Mortimer
authors.forename: J R
authors.initials: JR
authors.lastname: Levick
authors.forename: A
authors.initials: A
authors.lastname: Orlando
authors.forename: D O
authors.initials: DO
authors.lastname: Bates
mesh_terms: D002280:Basal Cell Carcinoma; D006801:Humans; D007150:Immunohistochemistry; D008198:Lymph Nodes / Q000033:anatomy & histology* / Q000473:pathology*; D042583:Lymphangiogenesis; D008545:Melanoma / Q000473:pathology*; D009362:Neoplasm Metastasis / Q000503:physiopathology*; D012878:Skin Neoplasms / Q000473:pathology*