Intraperitoneal metastases from cutaneous melanoma in a 2-year-old girl: A case report

Introduction

Cutaneous melanoma represents less than 1 % of all pediatric malignancies, with an incidence of 4.9 cases per million in children aged 0–4 years. Intraperitoneal metastasis is exceptionally rare in this population.

Case presentation

A 2-year-old female with a history of congenital hydrocephalus and a large congenital melanocytic nevus (CMN) over the lower back and buttocks developed oral intolerance, abdominal distension, and acute abdominal pain. The initial workup raised suspicion of ventriculoperitoneal (VP) shunt malfunction. Abdominal ultrasound and abdominal computerized tomography (CT) revealed free peritoneal fluid; no adnexal mass was identified preoperatively. She underwent an exploratory laparotomy during which we found an 8 × 7 × 7-cm right adnexal mass involving the right ovary, right fallopian tube, the omentum, and additionally there were multiple peritoneal nodules. Right salpingo-oophorectomy, omentectomy, and biopsy of peritoneal implants were performed. Histopathology confirmed a malignant small blue cell tumor positive for S100, HMB-45, and Melan-A, consistent with melanoma. No extracutaneous primary lesion was found. The final diagnosis was CMN-associated melanoma with intraperitoneal metastasis, stage IV. The patient recovered uneventfully, initiated systemic treatment, and remains under multidisciplinary follow-up.

Conclusion

Intraperitoneal metastasis must be ruled out in patients with congenital melanocytic nevus who develop abdominal pain, distension, or feeding intolerance.