An Unusual Case of Malignant Melanoma with Metastasis to the Placenta During Pregnancy

INTRODUCTION: We describe an unusual case of metastatic melanoma of the brain with an unknown primary site during pregnancy. CASE DESCRIPTION: A 35-year-old woman in the third trimester of pregnancy presented with ataxia, nausea, vomiting, headaches and diplopia. CT of the brain revealed a hyper-attenuating 2.1 cm mass in the fourth ventricle with mild obstructive hydrocephalus. A healthy newborn was delivered by urgent caesarean section. Craniotomy and resection of the brain lesion confirmed melanoma. Pathology of the placenta reported a ‘focal nest of melanocytes identified in intervillous space’. DISCUSSION: Brain and maternal placenta pathology findings were consistent with melanoma, making this case relevant because of the possibility of metastatic melanoma in a fetus. CONCLUSION: Epidemiological data on congenital and infantile melanoma are scarce. Also, there is no database for long-term follow-up of children born to pregnant mothers with metastatic melanoma. Delayed presentation of melanoma in the child cannot be ruled out. LEARNING POINTS: Melanoma brain metastasis is an uncommon initial presentation during pregnancy. During pregnancy, vague symptoms such as headaches and nausea can easily be attributed to the pregnancy itself rather than more serious conditions like cancer. Metastatic melanoma diagnosed during pregnancy with disease in the placenta is a rare occurrence and should trigger close follow-up of the neonate secondary to concerns of transplacental metastasis.