Gastro-intestinal metastasis from Melanoma: Clinico-pathological clues

Introduction: Metastasis from melanoma in the gastro-intestinal tract is a frequent event but, in the absence of an adequate clinical context and oncological anamnesis, it could be misdiagnosed by the pathologists. Moreover, amelanotic and/or poorly differentiated metastasis from melanoma in the gastro-intestinal tract can be easily underestimated.

Materials and methods: We describe the histological features of gastro-intestinal metastasis from melanoma in a multi-centric cohort of 49 patients. In 24/49 patients, we were able to compare histological findings such as the growth pattern and the melanotic pigment also in the primary melanoma.

Results: The epithelioid pattern is the most common growth pattern observed in gastro-intestinal metastasis (57 %), followed by the mixed pattern (41 %) and the spindled pattern (2 %). We documented a discordant growth pattern between metastasis and primary in 9/24 cases and the absence of melanotic pigment in 8/49 cases.

Discussion: Our experience highlights that pathologists should take into account the possibility of gastro-intestinal metastasis from melanoma also in cases with spindled-cells/amelanotic lesions, without a previous anamnesis of melanoma asportation, and in cases of a discordant growth pattern with the primary. A correct clinical integration and an aware immunohistochemical approach are imperative to best manage the bioptic sample in order to investigate the biological profiling and therefore plan a personalizated therapy.