Cutaneous lymphangiosarcoma in an African green monkey from St. Kitts, and a literature review

A 22-y-old, intact male African green monkey (Chlorocebus sabaeus) with a pedunculated cutaneous ulcerated spheroid mass on the left flank was autopsied. Histologically, the mass was infiltrative, with neoplastic cells forming empty vascular channels lined by a monolayer of polygonal neoplastic cells, many with eosinophilic intracytoplasmic granules, supported by abundant fibrous stroma. Immunohistochemically, neoplastic cells had strong immunolabeling with vimentin, moderate immunolabeling with LYVE1 and PROX1 antibodies, and no cytokeratin or CD31 immunolabeling. Ultrastructurally, a basal lamina was absent, nuclei had a 1:4 heterochromatin:euchromatin ratio, with a mild-to-moderate increase in thickness and asymmetrically distributed nuclear fibrous lamina, enlarged compacted nucleolus, round mitochondria, conspicuous rough endoplasmic reticulum, and membrane-bound electron-dense granules. Intercellular desmosomes were present in clusters of neoplastic cells. Lymphangiosarcoma has not been previously reported in non-human primates, to our knowledge. Our case highlights the importance of integrating histopathology, immunohistochemistry, and ultrastructural analysis to accurately diagnose rare vascular tumors, such as lymphangiosarcoma.