Citation for published version (APA): Francken, A. B. (2007). Primary and metastatic melanoma: aspects of follow-up and staging s.n.

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1 University of Groningen Primary and metastatic melanoma Francken, Anne Brecht IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document Version Publisher's PDF, also known as Version of record Publication date: 2007 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Francken, A. B. (2007). Primary and metastatic melanoma: aspects of follow-up and staging s.n. Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons). Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from the University of Groningen/UMCG research database (Pure): For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Download date:

2 Part II Primary Melanoma Staging

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4 Chapter 7 The prognostic importance of tumor mitotic rate confirmed in 1317 patients with primary cutaneous melanoma and long follow-up Anne Brecht Francken Helen M. Shaw John F. Thompson Seng-jaw Soong Neil A. Accort Manuela F. Azzola Richard A. Scolyer Gerald W. Milton William H. McCarthy Marjorie H. Colman Vincent J. McGovern Ann Surg Oncol 2004:11; Proefschrift.indb :57:40

5 Chapter 7 ABSTRACT Introduction The late Dr Vincent McGovern ( ) was an international authority on melanoma pathology and one of the first to suggest that assessment of tumor mitotic rate (TMR) might provide useful prognostic information. Data for a large cohort of patients, now with extended follow-up, whose tumors had been assessed by Dr McGovern, were analysed to reassess the independent prognostic value of TMR in primary localized, cutaneous melanoma. Methods Information was extracted from the Sydney Melanoma Unit database for 1317 patients treated between 1957 and 1982 who had complete clinical information and in whom primary lesion pathology, which included tumor thickness, ulcerative state and TMR, had been assessed by Dr McGovern. All these assessments were made according to the recommendations of the VIIIth International Pigment Cell Conference, held in Sydney in 1972 under the auspices of the International Union Against Cancer. Factors predicting melanoma-specific survival were analyzed using the Cox proportional hazards regression model. Results Stage, according to the recently revised American Joint Committee on Cancer Staging System (which is based on tumor thickness and ulceration) was the most predictive factor for survival (P<0.0001). This was followed by primary lesion site (P<0.0001), patient age (P=0.0005) and TMR (P=0.008). Conclusion TMR was confirmed to be an important independent predictor of survival in patients with primary cutaneous melanoma. However, its predictive value was less than it was when assessed according to the 1982 revisions of the 1972 TMR recommendations. 144

6 Prognostic importance of melanoma mitotic rate. INTRODUCTION When the International Union Against Cancer decided to hold its 1972 Interim Meeting in Sydney with the themes of Leukaemia and Skin Cancer-Melanoma, it was thought appropriate that the VIIIth International Pigment Cell Conference be held concurrently. As Chairman of the Pigment Cell Subcommittee, the Australian Cancer Society appointed a Sydney-based histopathologist, Dr Vincent McGovern (VMcG), 1 an internationally recognized authority on the histopathology of melanoma who had developed a close association with the Sydney Melanoma Unit (SMU) by virtue of this expertise. At this 1972 meeting the first organized discussion amongst histopathologists took place to consider ways of assessing prognosis based on features of a primary cutaneous melanoma, and it was agreed that the level of invasion, as proposed by Drs Wallace Clark and VMcG, correlated well with prognosis. Although subsequently referred to as Clark levels, VMcG had previously made fundamentally important contributions to the concept and later undertook major studies validating it. 2,3 The present study is based on other work undertaken by VMcG prior to his untimely death in a road accident on December 30, After the delineation by Dr Alexander Breslow (1970) of tumor thickness as the most important predictor of survival, 4 VMcG had been the first to undertake detailed analyses of the histologic features of primary melanomas that were potentially of prognostic significance These studies had included an examination of tumor mitotic rate (TMR) as a possible independent prognostic variable in a large cohort of SMU patients treated between 1957 and It was therefore considered useful to use this unique dataset, now with very long patient followup, to confirm the prognostic value of TMR that we recently demonstrated in a completely separate group of 3661 SMU patients treated from 1983 onwards. 13 Also, this seemed a valuable method of determining if TMR assessment according to 1982 recommendations, 14 used in the latter study, was more predictive of its prognostic strength than assessment according to the 1972 recommendations, 15 used in the present study. PATIENTS AND METHODS Patients All patients with cutaneous melanoma whose primary lesion pathology had been reviewed by VMcG were identified from the SMU database. There were approximately 4500 patients in total. Selected for detailed analysis were patients who had: 145

7 Chapter 7 1. Definitive treatment, ie wide excision of the primary lesion, by SMU surgeons (GWM or WHMcC) between 1957 and 1982 at either Royal Prince Alfred, St Vincents or Sydney Hospital. Patients initially treated elsewhere and presenting to the SMU later in the course of their disease because of recurrence were excluded from the analysis to minimize referral bias. 2. Only one primary, invasive, cutaneous melanoma. 3. Localized disease, i.e. clinical and/or pathologic stage I or II according to the most recent American Joint Committee on Cancer (AJCC) Melanoma Staging System. 16 Pathology The microscope used by VMcG was a Zeiss instrument with a high power magnification of x300. For the purpose of the present study, this microscope s HPF diameter was determined and found to be 0.79mm. For each melanoma reported, VMcG recorded 14 pathologic variables; these included tumor thickness, presence or absence of ulceration, TMR and, where practical, Clark level of invasion. For the present study tumor thickness results were grouped as recommended in the most recent revision of the AJCC staging system and coded as 1: 1.0mm, 2: mm, 3: mm and 4: >4.0mm. Ulceration was coded as 0: absent and 1: present. The AJCC staging (combining tumor thickness and ulceration) was used as a covariate in the Cox model, since it is now becoming generally accepted that this provides a far more accurate indicator of survival than is achieved by considering tumor thickness and ulceration separately. Coding for this variable was: 1: stage IA, 2: stage IB, 3: stage IIA, 4: stage IIB and 5: stage IIC. The method used by VMcG to determine TMR was based on the recommendations of the 1972 International Pigment Cell Conference for the classification of malignant melanoma 15. The average number of mitoses in at least 10 high power (x300) fields over the entire dermal component of the lesion was obtained and then expressed as the number of mitoses/5hpf. In the case of small melanomas, where the dermal component was < 10HPF, the entire melanoma was assessed. The TMR was coded as 1: 0 mitoses/5hpf, 2: 1-4 mitoses/5hpf and 3: 5 mitoses/5hpf. Since the microscope used by VMcG had a HPF diameter of 0.79mm, the area of its HPF was 0.49mm 2 which approximated to 1: 2 mitoses/mm 2, 2: >2-8 mitoses/mm 2 and 3: >8 mitoses/mm 2 in the subsequent 1982 Pathology Workshop recommendations

8 Prognostic importance of melanoma mitotic rate. Other putative prognostic variables Age was coded in deciles as 1: years, 2: years...7: years and 8: 80 years. Gender was coded as 0: male, 1: female, anatomic site of primary lesion as 0: extremities, 1: trunk, head or neck, and Clark level as 2, 3, 4 or 5. Survival Follow-up status was taken from the patient s last follow-up date and coded as 1: alive, or dead from an unrelated cause and 2: dead from melanoma. Comparison of results from the two SMU studies of TMR. The series 13 analyzed data for patients treated at the SMU from 1983 onwards, and was therefore based on a patient population completely separate from the present analysis. Comparisons were made of clinical and pathologic factors between the two series, as well as the 10-year survival rates according to AJCC stage. Results of the Cox model analysis of prognostic factors derived from the present study were compared to the two Cox model results derived from the series, in which two methods of grouping TMR were tested, to determine which would provide the more useful way of demonstrating the prognostic strength of this variable. These methods of grouping were A, (mitosis groupings 1: 0 mitoses/ mm 2, 2: 1-4 mitoses/mm 2, 3: 5-10 mitoses/mm 2 and 4: 11/mm 2 ) and B, (mitosis groupings 1: 0-1 mitoses/mm 2, 2: 2-4 mitoses/mm 2 and 3: 5 mitoses/mm 2 ). Statistical analysis The methods for statistical analysis used in the present study were identical to those used in the series 13 and those used to validate the most recent AJCC staging system. 17 RESULTS A total of 1317 patients satisfied the study selection criteria, but 106 were excluded from the Cox analysis due to missing variables, notably Clark level of invasion (n=100). A positive result (uncensored in the Cox analysis) was recorded in 204 patients, making the ratio of uncensored to total patients Median follow-up since 1957 for uncensored patients was 4.5 years (range years) and for censored patients, 13.8 years (range years). Figure 1 shows the cumulative proportion of 204 stage I and stage II uncensored patients dying according to time. Deaths from melanoma continued to occur even after 15 years in stage I patients. 147

9 Chapter 7 Figure 1. The cumulative proportion of 204 stage I and stage II uncensored patients dying according to time. Table 1 shows the distribution of clinical and pathologic factors in the present study compared to their distribution in the series. There were no marked differences in these distributions. Figure 2 shows the step-wise decline in 10-year survival rates according to the revised AJCC pathologic stage groupings in each study. There were no significant variations in these survival rates between the two series. Table 1. Distribution of Clinical and Pathologic Factors in Present Study and TMR STUDY I a Present study TMR STUDY I CLINICAL FACTORS Site of primary lesion Head, neck and trunk Age > 59 years Gender Male PATHOLOGIC FACTORS Thickness > 2.0 mm Ulceration Present Mitotic rate to 1 mitoses/5hpf b 56 > 2 mitoses/mm 2 c

10 Prognostic importance of melanoma mitotic rate. Figure 2. A comparison of 10-year survival rates according to AJCC stage for 1317 patients with localized, cutaneous melanoma in the present ( ) study and 3661 patients with localized, cutaneous melanoma in the study. Figure 3 shows the decline in proportion of patients surviving according to TMR groups in the present study. There was a significant difference in survival between each group. (P<0.0001). The Cox model analysis of prognostic factors derived in the present study indicated that AJCC stage (based on tumor thickness and ulceration) was the most important predictor of survival, followed by primary lesion site, age of the patient and, to a slightly lesser extent, TMR (Table 2). Clark level and patient gender were not significant as independent prognostic factors. In comparison, from the Cox Figure 3. Melanoma-specific survival curves for the 1317 patients with localized, cutaneous melanoma in the present study according to TMR groupings. 149

11 Chapter 7 Table 2: Cox Regression Analysis of prognosis for 1211 Melanoma Patients with Localized Disease Variable Chi-square value (Wald) P value Risk ratio 95% CL Stage (AJCC) < Site of primary lesion < Age Mitotic rate a Level of invasion Gender Table 3: Cox Regression Analysis of prognosis for 3575 Melanoma Patients with Localized Disease According to Method A in TMR STUDY Ib Variable Chi-square value (Wald) P value Risk ratio 95% CL Stage (AJCC) < Mitotic rate b < Age < Gender Site of primary lesion Level of invasion Table 4: Cox Regression Analysis of prognosis for 3575 Melanoma Patients with Localized Disease According to Method B in TMR STUDY Ic Variable Chi-square value (Wald) P value Risk ratio 95% CL Stage (AJCC) < Age < Mitotic rate c Gender Site of primary lesion Level of invasion Tables 2, 3 and 4: CL: confidence limits Stage (AJCC)1: IA, 2: IB, 3: IIA, 4: IIB, 5: IIC Site of primary lesion- 0:Lower and upper extremities,1:trunk/head and neck Age-deciles: 1:10-19, 2: : and 8: to 80 years Level of invasion- 0: II, 1: III, 2: IV, 3: V Gender- 0: female, 1: male Table 2: a Mitotic rate- 0: 0/5HPF 1: 1-4/5HPF, 2: >or equal to 5/5HPF Table 3: b Method A in TMR STUDY I: Method A in tumor mitotic rate study I 13. 1: 0/mm2, 2: 1-4/mm2, 3: 5-10/mm2, 4: to 11/mm2 Table 4: c Method B in TMR STUDY I: Method B in tumor mitotic rate study I 13. 1: 0-1/mm2, 2: 2-4/mm2, 3: to 5/ mm2 150

12 Prognostic importance of melanoma mitotic rate. models of prognostic factors derived from methods A and B groupings of TMR in the series, AJCC stage was again the most important determinant of survival in both methods of grouping (Tables 3 and 4 respectively). However, TMR was the second most dominant prognostic variable using method A grouping, whilst it fell to third in rank importance using method B grouping. DISCUSSION The present analysis of TMR as assessed by VMcG using the 1972 consensus classification criteria confirmed that this variable was an important prognostic factor. It was a less dominant determinant of outcome than demonstrated in the series, and it seems most likely that the different method of assessing TMR (1972 versus 1982 recommendations) was responsible for this reduction of prognostic importance. However, there were other factors that may have been responsible for this. It is instructive to examine these issues in detail. TMR assessment and groupings The recommendations of the 1972 consensus were followed in assembling the data used in the present study, since VMcG s reviews of these 1317 primary melanomas were all performed prior to the 1982 meeting. The method used in the series, on the other hand, was to count the total number of mitoses/mm 2 in the dermal area of the tumor with the highest TMR. This method of assessment was the recommendation of the 1982 Pathology workshop held in Sydney, convened and chaired by VMcG and attended by other prominent international histopathologists with an interest in melanoma. The participants in this Workshop considered that their revised method of assessing TMR would be independent of the microscope and magnification used, and that results obtained in different parts of the world would therefore become more comparable. The SMU histopathologists involved in the series also believed that this method was more accurate and scientifically valid, being particularly useful in the assessment of tumors in which only rare (or a single) dermal mitosis was present in the entire specimen. Using the 1972 classification, such cases would defy subgrouping, as the average TMR would be >0 but <1/10HPF. Such cases would be classified in VMcG s grouping as 0 mitoses/5hpf. Also, in this earlier classification, there was a tacit assumption that there was not a wide variation in the area of a HPF for the microscopes used to assess TMR. This has clearly been shown to be incorrect, with TMR expressed as the number of mitoses/10hpf varying by as much as 600%, depending on the particular microscope used. 18 Furthermore, the 1982 consensus method is similar to that recommended for the counting of TMR in other solid tumors, 19 and for these 151

13 Chapter 7 reasons the SMU histopathologists recommended its use in determining the TMR of cutaneous melanomas. In the series, there was a significant prognostic difference between a TMR of 0 mitoses/mm 2 and a TMR of 1 mitosis/mm 2, but not between 1 and 2 mitoses/mm 2, 2 and 3 mitoses/mm 2, 3 and 4 mitoses/mm 2 and 4 and 5 mitoses/ mm 2. Attempts were made in that study to determine the optimal groupings of TMR which would demonstrate its true prognostic significance. Method A groupings were 1: 0 mitoses/mm 2, 2: 1-4 mitoses/mm 2, 3: 5-10 mitoses/mm 2 and 4: 11 mitoses/mm 2, whilst method B groupings were 1: 0-1 mitoses/mm 2, 2: 2-4 mitoses/mm 2 and 3: >or equal to 5 mitoses/mm 2. It was found that by grouping TMR according to method A, this variable proved to be second only to tumor thickness in prognostic importance. On the other hand, grouping TMR according to method B, which combined 0 and 1 mitosis/mm 2, caused TMR to fall to third in rank importance. It is important to note that the lower prognostic significance derived in the present study, in which 0, 1 and 2 mitoses/mm 2 were grouped together, followed the same pattern as that previously obtained using method B in the series. Another difference between these two SMU studies was in the number of histopathologists involved in determining TMR in each case. In the series, five histopathologists contributed, whereas in the current study, all reviews were made by VMcG, which may have reduced variability in assessing TMR. However, a recent SMU review carried out amongst six histopathologists with varying experience in assessing TMR in melanomas revealed that there was excellent concordance between these histopathologists in assessing this variable. 20 Therefore, differences in the methods of assessing TMR and the TMR groupings used in each of the two studies, rather than interobserver variability, were probably the most important factors in determining the significance of the results. Other factors Although the two series were superficially similar in patient composition, they were not identical, probably due mainly to temporal differences in referral patterns to the SMU. The present series spanned a period of time ( ) when almost all patients were referred to a hospital for initial assessment and excision of their primary lesion. More recently, primary lesion excisions are commonly performed by family practitioners or dermatologists and patients are referred to a specialist treatment center such as the SMU only if more extensive definitive treatment is required. Thus the present series could be regarded as more population based than the series, reported previously. In the present 152

14 Prognostic importance of melanoma mitotic rate. study, 34% of patients were pathologically staged. This figure is a reflection of the proportion of patients with intermediate to high risk tumours (>1.5mm thickness), 95% of whom underwent elective lymph node dissection (Table 1). The remaining 66% were clinically staged patients whose tumours were 1.5 mm in thickness and who therefore would have had a relatively low risk of harboring lymph node metastases (6% in a recent unpublished review of SMU sentinel node biopsy data). In the study, 34% of patients were also pathologically staged. However, the proportion of tumours > 1.5mm in thickness in this latter study was somewhat higher (46%) than the proportion pathologically staged (Table 1). This was because after 1992, according to the randomization requirements of the Multicenter Selective Lymphadenectomy Trial 21 in which the SMU participated, only 60% of patients with tumors 1mm in thickness were pathologically staged, by sentinel lymph node biopsy. This could have had a bearing on the slight differences in clinical and histopathologic factors between the two series. A major feature which varied between the two analyses and which seems likely to have been responsible for differences in the rank importance of prognostic factors, however, was the prolonged follow-up in the present study (overall median of 13.8 years for censored patients). As an example, one can examine the prognostic prominence of primary lesion site in the present study and its relative lack of importance in the series. It has been amply demonstrated that with long follow-up, 10-year survival rates for patients with extremity lesions are significantly higher than for patients with lesions on the trunk, head or neck. 22,23 In the present study, patients with extremity lesions and short follow-up (5 years) had a 4.3% higher survival rate than those with lesions on the trunk, head or neck. However, the difference at 10 years rose to 12.7%. In contrast, in the series, the prognostic advantage of this lesion location was less perceptible after 10 years (4.7%). Thus the longer the follow-up, the more apparent will the prognostic significance of this variable become. The present study confirmed our initial findings on the prognostic importance of TMR that was demonstrated in the series. However, its relative strength as a prognostic factor was diminished, primarily due to the method used for its estimation. As described in detail in the series, several recent studies have also attempted to assess its prognostic value Nevertheless, since the submission for publication of the series, additional studies have appeared in the literature which support the role of TMR as a powerful prognostic variable. In their multivariate analysis of 1284 stage I - III patients, Retsas et al 31 attempted to validate the AJCC proposal for the introduction of ulceration of the primary cutaneous melanoma as an independent prognostic factor. During the course of this study they found, by analyzing both tumor thickness and TMR as continuous variables, that TMR (assessed as the number of mitoses/mm 2 ) was 153

15 Chapter 7 second only to tumor thickness in predicting overall survival (P<0.005 versus P< respectively). The current consensus is that the status of sentinel nodes is the most important predictor of survival in patients with melanoma. The role of TMR in predicting sentinel lymph node positivity and positivity of non-sentinel nodes upon CLND is gradually emerging, as new information is reported. Sabel et al, 32 assessing TMR by recording the number of mitoses per HPF, found that in addition to tumor thickness, both TMR and younger age were highly predictive of sentinel node positivity in 423 stage I-II patients (P<0.0001, P< and P<0.003 respectively). Similarly, a recent small study of 6 patients with thin primary tumors (<1.0mm thick) and positive sentinel nodes, 33 revealed that ulceration, vertical growth phase and high TMR rate were major factors in influencing sentinel node positivity (P=0.019, P=0.002 and P=0.008 respectively). A univariate analysis of histologic factors affecting non-sentinel node positivity in 191 patients from the SMU patients with primary tumors of any thickness 34 indicated that there was a trend for increasing TMR to be associated with a greater risk of non-sentinel node positivity. None of the above studies were particularly large and, if they included multivariate analyses, they may not have adhered to Vollmer s strict guidelines for performing such analyses, as described in detail in the report of our series. 35 Nevertheless, at this stage it seems probable that TMR is an important independent indicator of the metastatic potential of a melanoma and the patient s ultimate prognosis. If this is validated by rigorous analyses from other centers in which TMR is assessed according to the 1982 recommendations, TMR should logically be included in all determinations of prognosis and perhaps integrated into future melanoma staging systems. 154

16 Prognostic importance of melanoma mitotic rate. References 1. McGovern VJ, Russell P. Mechanisms in pigmentation. In: Riley V, ed. Pigment cell. Vol. 1. Basel: Karger, McGovern VJ. The classification of melanoma and its relationship with prognosis. Pathology 1970; 2: McGovern VJ. Melanoma: growth patterns, multiplicity and regression. In: McCarthy WH, ed.. Melanoma and skin cancer. Proceedings of the International Cancer Conference. Sydney: Blight, Government Printer, 1972; Breslow A. Thickness, cross sectional areas an depth of invasion in the prognosis of cutaneous melanoma. Ann Surg 1970; 172: McGovern VJ, Shaw HM, Milton GW et al. Prognostic significance of the histological features of malignant melanoma. Histopathology 1979; 3: McGovern VJ, Shaw HM, Milton GW et al. Is malignant melanoma arising in Hutchinson s melanotic freckle a separate disease entity? Histopathology 1980; 4: McGovern VJ, Shaw HM, Milton GW et al. Histological assessment of prognosis in clinical stage cutaneous malignant melanoma. In: Seiji M, ed. Pigment cell. Vol. 4. Phenotypic expression in pigment cells. Tokyo: University of Tokyo Press, 1981; McGovern VJ, Shaw HM, Milton GW et al. Cell type and pigment content as prognostic indicators in cutaneous malignant melanoma. In: Ackerman AB, ed. Pathology of malignant melanoma. New York: Masson, 1981; McGovern VJ, Shaw HM, Milton GW et al. Lymphocytic infiltration and survival from malignant melanoma. In: Ackerman AB, ed. Pathology of malignant melanoma. New York: Masson, 1981; McGovern VJ, Shaw HM, Milton GW et al. Ulceration and prognosis in cutaneous malignant melanoma. Histopathology 1982; 6: McGovern VJ, Shaw HM, Milton GW. Prognostic significance of a polypoid configuration in malignant melanoma. Histopathology 1983;7: McGovern VJ, Shaw HM, Milton GW. Prognosis in patients with thin malignant melanoma: influence of regression. Histopathology 1983; 7: Azzola MF, Shaw HM, Thompson JF et al. Tumor mitotic rate is a more powerful prognostic indicator than ulceration in patients with primary cutaneous melanoma. Cancer 2003; 97: McGovern VJ, Cochran AJ, Van Der Esch EP et al. The classification of malignant melanoma, its histological reporting and registration: a revision of the 1972 classification. Pathology 1986; 18: McGovern VJ, Mihm MC, Bailly C et al. The classification of melanoma and its histologic reporting. Cancer 1973; 32: Balch CM, Buzaid AC, Soong S-J et al. Final version of the American Joint Committee on Cancer Melanoma Staging System for Cutaneous Melanoma. J Clin Oncol 2001; 19: Buzaid AC, Ross MI, Balch CM et al. Critical analysis of the current AJCC staging system for cutaneous melanoma and proposal of a new staging system. J Clin Oncol 1997; 15:

17 Chapter Ellis PSJ, Whitehead R. Mitosis counting - a need for reappraisal. Hum Pathol. 1981; 12: Hilsenbeck S, Allred D. Improved methods of estimating mitotic figures in solid tumours. Hum Pathol 1990; 21: Scolyer RA, Shaw HM, Thompson JF, et al. Inter-observer reproducibility of histopathologic prognostic variables in primary cutaneous melanomas. Am J Surg Pathol (in press). 21. Multicenter Selective Lymphadenectomy Trial. National Cancer Institute Grant No. PO1 CA Stadelmann WK, Rapaport DP, Soong S-J et al. Prognostic clinical and pathologic features. In: Balch CM, Houghton AN, Sober AJ, Soong S- J, eds. Cutaneous melanoma. St Louis: Quality Medical Publishing, Inc, 1998; Soong S-J, Shaw HM, Balch CM et al. Predicting survival and recurrence in localized melanoma: a multivariate approach. World J Surg 1992; 16: Vossaert KA, Silverman MK, Kopf AW et al. Influence of gender on survival in patients with stage I malignant melanoma. J Am Acad Dermatol 1992; 26: MacKie RM, Aitchison T, Sirel JM et al. Prognostic models for subgroups of melanoma patients from the Scottish Melanoma Group database , and their subsequent validation. Br J Cancer 1995; 71: Barnhill RL, Fine JA, Roush GC et al. Predicting five-year outcome for patients with cutaneous melanoma in a population-based study. Cancer 1996; 78: Ostmeier H, Fuchs B, Otto F et al. Can immunohistochemical markers and mitotic rate improve prognostic precision in patients with primary melanoma? Cancer 1999; 85: Wagner JD, Gordon MS, Chuang T-Y et al. Predicting sentinel and residual lymph node basin disease after sentinel lymph node biopsy for melanoma. Cancer 2000; 89: Massi D, Borgognoni L, Franchi A et al. Thick cutaneous malignant melanoma: a reappraisal of prognostic factors. Melanoma Res 2000; 10: Schmidt-Wendtner MH, Baumert J, Schmidt M, Plewig G, Volkenandt M, Holzel D. Prognostic index for cutaneous melanoma: an analysis after follow-up of 2715 patients. Melanoma Res 2001; 11: Retsas S, Henry, Mohammed MQ, MacRae K. Prognostic factors of cutaneous melanoma and a new staging system proposal by the AJCC. Eur J Cancer 2002; 38: Sabel MS, Taylor JM, Grover AC et al. Mitotic rate and younger age are predictors of sentinel lymph node positivity. Ann Surg Oncol 2003; 10(suppl):S Oliveira RS, Ferreira LM, Biasi LJ et al. Vertical growth phase and positive sentinel node in thin melanoma. Braz J Med Biol Res 2003; 36: Shaw HM, Thompson JF. Frequency of nonsentinel lymph node metastasis in melanoma. Ann Surg Oncol 2002; 9: Vollmer RT. Malignant melanoma. A multivariate analysis of prognostic factors. Pathol Annu 1988; 24:

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