The complex relationships between sentinel node positivity, patient age, and primary tumor desmoplasia: analysis of 2303 melanoma patients treated at a single center.

BACKGROUND: Recent studies have shown that younger age is associated with a greater likelihood of positive sentinel node (SN) status in patients with localized melanoma. This is a paradoxical situation because it is well known that younger patients have a far more favorable overall survival rate than older patients. In addition, desmoplastic melanomas are associated with a lower frequency of SN positivity, although this is less well documented.
METHODS: The outcome for 2303 cutaneous melanoma patients undergoing sentinel lymph node biopsy (SLNB) at the Sydney Melanoma Unit between 1993 and 2006 was examined to clarify the role of patient age and desmoplastic histogenetic type on SN positivity.
RESULTS: By univariate analysis, patients aged <40 years had a higher SN positivity rate (22.6%) than patients aged > or =40 years (15.4%; P < .004). Features associated with SN positivity were tumor thickness, mitotic rate, ulcerative state, and nondesmoplastic histogenetic type (all P < .001). Patient sex and primary melanoma site were not statistically significantly associated. Multivariate analyses revealed that only tumor thickness, patient age, nondesmoplastic type (all P < .001), and ulceration (P < .026) were independently associated with SN positivity. Key prognostic determinants such as total number of disease-positive nodes (both SNs and non-SNs) and site of first relapse did not vary according to age.
CONCLUSIONS: Tumor thickness, patient age, desmoplastic histogenetic type, and primary melanoma ulceration were all independently associated with SN status. The factors underlying the paradox of a poorer survival rate in older patients despite a lower incidence of positive SNs remain unclear.