Among visceral metastatic sites, cutaneous
melanoma (CM) metastasises initially to the liver in ~14-20% of cases. Liver
metastases in CM patients are associated with both poor prognosis and poor response to
immunotherapy. Histopathological growth patterns (HGPs) of liver
metastases of the replacement and desmoplastic type, particularly from
colorectal cancer and
uveal melanoma (UM), may impart valuable biological and prognostic information. Here, we have studied HGP in 43 CM liver
metastases resected from 42 CM patients along with other prognostic factors from three institutions. The HGPs (replacement, desmoplastic, pushing) were scored at the
metastasis-liver interface with two algorithms: (1) 100% desmoplastic growth pattern (dHGP) and any (≥1%) replacement pattern (any-rHGP) and (2) >50% dHGP, >50% rHGP or mixed (<50% dHGP and/or rHGP, pushing HGP). For 1 patient with 2
metastases, an average was taken to obtain 1 final HGP yielding 42 observations from 42 patients. 22 cases (52%) had 100% dHGP whereas 20 (48%) had any replacement. Cases with rHGP demonstrated vascular co-option/angiotropism. With the development of liver
metastasis, only rHGP (both algorithms), male gender and positive
resection margins predicted diminished overall survival (p = 0.00099 and p = 0.0015; p = 0.034 and p = 0.024 respectively). On multivariate analysis, only HGP remained significant. 7 of 42 (17%) patients were alive with disease and 21 (50%) died with follow-up after liver
metastases ranging from 1.8 to 42.2 months (mean: 20.4 months, median: 19.0 months). 14 (33%) patients with previously-treated metastatic disease had no evidence of disease at last follow up. In conclusion, we report for the first time replacement and desmoplastic HGPs in CM liver
metastases and their prognostic value, as in UM and other solid
cancers. Of particular importance, any rHGP significantly predicted diminished overall survival while 100% dHGP correlated with increased survival. These results contribute to a better understanding of the biology of CM liver
metastases and potentially may be utilised in managing patients with these
metastases.