Abstract
purpose. To investigate the relationship between progression to hepatic metastasis and tumor-infiltrating macrophages and microcirculation attributes in uveal melanoma, a cancer that almost invariably disseminates hematogenously to the liver.
methods. A cross-sectional histopathologic analysis of 48 hepatic metastases and corresponding primary choroidal and ciliary body melanomas was conducted, by using statistical tests appropriate for paired data. Main outcome measures were the number and type of CD68-immunopositive, tumor-infiltrating macrophages, extravascular matrix loops and networks identified with periodic acid-Schiff stain, and microvascular density (MVD) counted as the number of discrete structures labeled by monoclonal antibody QBEND/10 to the CD34 epitope.
results. Hepatic metastases had a significantly lower grade of pigmentation (P < 0.0001), more frequent epithelioid cells (P = 0.0027), more intermediate and dendritic types of CD68-immunopositive macrophages than round ones (P = 0.0031), and a higher MVD (median difference, 15 counts more/0.313 mm2, P = 0.0003) than the primary uveal melanomas that spawned the metastases. The frequency of tumors with extravascular loops and networks did not increase on metastasizing. The survival of the patient after diagnosis of disseminated disease tended to be shorter if hepatic metastases had a high MVD (P = 0.098), adjusting for the size of the specimen.
conclusions. Of the markers studied, the presence of epithelioid cells and MVD most closely parallel progression of uveal melanoma from primary tumor to metastasis. These two tumor characteristics may be interrelated, and high MVD may help to predict survival after detection of hepatic metastases. The results also suggest that the grade of pigmentation and morphologic type of tumor-infiltrating macrophages are interrelated.
The evidence suggests that choroidal and ciliary body melanoma disseminates several years before diagnosis.
1 2 It metastasizes almost invariably hematogenously and in up to 95% of the patients initially to the liver.
3 4 5 6 The presence of epithelioid cells, extravascular matrix patterns that reflect the arrangement of tumor microcirculation,
7 8 9 10 high microvascular density (MVD),
11 12 13 and large numbers of tumor-infiltrating macrophages
14 15 in primary uveal melanoma are independently associated with shorter time to metastatic death than the absence of these characteristics. These associations may be either markers of aggressive tumors without direct contribution to the metastatic cascade or they may indicate direct participation in tumor progression to metastasis.
Despite treatment with current chemotherapy regimens, patients with metastases from uveal melanoma usually die within 2 to 14 months after the diagnosis of disseminated disease by routine screening.
16 17 18 The prognosis has improved only scantly over the decades, and part of the apparent improvement is likely to reflect lead-time bias from screening.
17 A need exists to better understand the biology of and factors contributing to progression of disseminated uveal melanoma. One way to increase understanding of progression from primary to metastatic melanoma in humans is to compare how tumor characteristics change on dissemination. One study has compared extravascular matrix patterns in primary and metastatic choroidal and ciliary body melanomas, but it did not compare this attribute within patients.
19 We undertook a paired analysis of primary choroidal and ciliary body melanomas and their corresponding hepatic metastases to test the hypothesis that microcirculation attributes and macrophage infiltration increase in grade with progression of primary tumor to metastasis. We also studied the association of microcirculatory attributes with survival after diagnosis of metastatic uveal melanoma.
The study complied with the tenets of the Declaration of Helsinki and was approved by the Institutional Review Board. All patients with a choroidal and ciliary body melanoma for which they had undergone enucleation of an eye in the district of the Helsinki University Central Hospital between 1962 and 1981 and later had metastasis were eligible. Enucleation was the standard treatment for all but the smallest melanomas during this period, making the series essentially population-based and unselected.
Inclusion criteria were that at least 50% of the primary tumors remained in the tissue block, and the remaining part was not entirely on the vitreal side of Bruch’s membrane,
10 and that one or more core-needle biopsy, biopsy, or autopsy specimens with a surface area of at least 0.35 mm
2 was available from hepatic metastases. This is roughly the minimum area needed to measure MVD.
12
During the study period, 292 consecutive patients had an eye with a choroidal and ciliary body melanoma removed, and 145 of these patients had metastases that were cytologically or histologically confirmed in 92 of them. Forty-eight pairs of primary tumors and hepatic metastases that fulfilled the inclusion criteria were identified (inclusion ratio, 33% of all patients with metastases: 29 women and 19 men).
The metastases had been recognized by liver imaging or laparoscopy after they caused symptoms. The original size of the biopsied and autopsied metastases was not recorded and, except in one case, the entire metastasis was not present in the specimen. The largest diameter in the biopsy specimen was measured from the sections with a pair of calipers. Of the 48 sections, 3 (6%) were obtained by core needle biopsy, 18 (38%) by surgical biopsy, and 27 (56%) at autopsy. The mean and ranges of specimen sizes for these three groups were 2 mm (range, 1.5–3), 7 mm (range, 2–18.5), and 20 mm (range, 6.5–35), respectively.
The disease-free interval was calculated as the time from enucleation to diagnosis of metastases, and overall survival as the time from the date of diagnosis of metastases to death. It was possible to calculate these intervals in the 22 patients who had undergone a biopsy rather than an autopsy.
All analyses were performed with the Stata (release 7.0; Stata Co., College Station, TX) and StatXact-3 (Cytel Co., Cambridge, MA) statistical software packages. P < 0.05 was considered statistically significant, and all tests were two-tailed.
The median and range are given as descriptive statistics. The Wilcoxon signed-rank test was used to compare distributions of paired continuous data and the Stuart-Maxwell test and test for trend to compare unordered and ordered paired contingency tables, respectively.
27 Spearman’s rank correlation was used to analyze interrelationships between two variables. The Mann-Whitney
U-test was used to compare disease-free intervals between categories.
Overall survival was analyzed with the Kaplan-Meier product-limit method and log-rank test. MVD was divided into two groups according to the median. Cox regression was used to adjust for the size of the metastatic specimen.