The pathology of melanoma as a basis for prognostic models: the UCSF experience

Selective sentinel lymph node dissection for melanoma: importance of harvesting nodes with lower radioactive counts without the need for blue dye

BACKGROUND

Determining how many sentinel lymph nodes (SLNs) should be removed for melanoma is important. The purpose of this study is to determine the frequency at which nodes that are less radioactive than the "hottest" node (which is negative) are positive for melanoma, how low of a radioactivity should warrant harvest, and if isosulfan blue is necessary.

METHODS

We reviewed 1,152 melanoma patients who underwent lymphoscintigraphy with technetium, with or without blue dye, and SLN dissection from 1996 to 2008. SLNs with radioactivity ≥10% of the "hottest" SLN, all blue nodes, and all suspicious nodes were removed and analyzed. The miss rate was calculated as the proportion of node positive cases in which the "hottest" SLN was negative.

RESULTS

SLNs were identified in 1,520 nodal basins in 1,152 patients. SLN micrometastases were detected in 218 basins (14%) in 204 patients (18%). In 16% of SLN-positive patients (33/204 patients), the positive SLN was found to have a lower radioactive count than the "hottest" SLN, which was negative. In 21 of these cases, the positive SLNs had radioactivity ≤50% of the "hottest" SLN. The 10% rule significantly reduced the miss rate to 2.5% compared with removal of only the "hottest" SLN (miss rate = 16%). Also, blue dye did not significantly decrease the miss rate compared with radiocolloid alone using the 10% rule.

CONCLUSIONS

To decrease the miss rate, all SLNs with ≥10% of the ex vivo radioactivity of the "hottest" SLN should be removed and blue dye is not essential.

Prognostic significance of extent of ulceration in primary cutaneous melanoma

Ulceration has been shown to be an adverse prognostic factor in primary cutaneous melanoma. However, the extent of ulceration required for histologic identification and biologic significance is unclear. We examined the impact of extent of ulceration on melanoma outcome in a cohort of 235 melanoma patients by evaluating the relationship between percentage of ulceration in the vertical growth phase of the primary tumor and 2 outcome parameters: sentinel lymph node status and overall survival. We measured the diameter of the ulcerated area in millimeters over the diameter of the entire vertical growth phase. There was a statistically significant relationship between increasing percentage of tumor ulceration and both sentinel lymph node status as well as overall survival, with a binary cut-off point of 2% for sentinel lymph node status and 5% for overall survival. The percentage of ulceration provides additional prognostic information in predicting sentinel lymph node status and in determining survival in melanoma patients. These results suggest that no more than minimal ulceration is required to have a prognostic impact on melanoma survival.

Primary cutaneous malignant melanoma and its precursor lesions: diagnostic and therapeutic overview

During the past few decades, scientific data relating to melanoma have flourished. New information regarding acquired nevi, dysplastic nevi (atypical nevi), and congenital nevi has given us a better understanding of these precursor lesions and their relationships to malignant melanoma. The roles of laboratory testing, photography, and newer diagnostic tools (eg, epiluminescence) to evaluate patients for melanoma or precursor lesions have fallen under close scrutiny. Traditional surgical therapeutic interventions continue to be replaced by less aggressive protocols based on prospective randomized studies. Many new interventions such as sentinel lymph node procedures are currently being evaluated at research/referral centers around the world. We present clinicians with an evidence-based summary of the current literature with regard to primary cutaneous melanoma, its diagnosis, precursor lesions, and therapy.

Prediction of outcome for patients with cutaneous melanoma

Most patients with primary melanoma are cured by local surgery, but a significant minority develop fatal metastases. The ability to identify patients with progressive disease is central to efficient management: permitting optimal deployment of adjunctive therapy and sparing the non-progressing majority the morbidity of aggressive therapy. Accurate prediction on an individual patient basis is the ideal, but the best current prognosticators permit only assignment to risk categories. Formulaic combinations of well tried correlates of outcome (gender, ulceration, depth, thickness, and mitotic rate increase accuracy of prediction, but not to personalised level. The use of large data bases against which the attributes of individual patients may be compared is useful and amalgamation of data bases will increase the availability of this approach. The development of markers of proliferation fraction (PCNA and MIB-1) and of the metastatic phenotype (PNA-receptor status) will further refine the process. Staging of disease is critical. Accuracy of staging is improved by mapping the (sentinel) lymph nodes likely to contain early tumor by lymphoscintigraphy and dye/radiomarker localisation. The application of exquisitely sensitive immunohistochemical and molecular biological techniques to biopsies from tissues likely to be the site of metastases permit assessment of clinical stage with a previously impossible degree of accuracy (ultrastaging).

The multidisciplinary melanoma center

The evolution of the multidisciplinary melanoma clinics from 1965 to the present is reviewed. The University of California Melanoma Center database is presented as a model of actual visualization of the data in the care of individual melanoma patients. The basis of the ideal melanoma multidisciplinary center is given with common attributes that could be shared among all clinics, thus establishing a national network of such clinics.