Amelanotic Melanoma Arising in Surgical Cicatrix: A Case Report

Abstract

Introduction: Amelanotic melanoma (AM) is a rare subtype of melanoma characterized by the absence of pigmentation, making it difficult to diagnose. This case report describes AM arising in a cicatrix following cardiac surgery, highlighting diagnostic challenges and the importance of reassessment when the clinical findings do not fit the initial diagnosis.

Case presentation: A 76-year-old male underwent coronary artery bypass grafting in March 2022. Nine months later, he noticed a mass with ulceration in the sternal cicatrix. A punch biopsy showed inflammation and fibrosis, leading to a diagnosis of suture granuloma. Despite the lesion's progression over 8 months, no further biopsies or treatments were performed. In September 2023, the patient was referred to the Department of Plastic Surgery at Copenhagen University Hospital, Rigshospitalet, where an excision biopsy revealed an AM with a thickness of 20 mm. Preoperative PET-CT showed no evidence of metastasis, and re-excision with sentinel lymph node biopsy was performed. Adjuvant oncologic treatment was administered due to a positive sentinel node.

Conclusion: This case emphasizes the diagnostic challenges of AM, especially when arising in a cicatrix. When the clinical picture does not align with the initial diagnosis, it is crucial to reconsider and conduct further evaluations to avoid delays in treatment.

Keywords: Amelanotic melanoma; Case report; Cicatrix; Marjolin’s ulcer; Neoplasm.

Fig. 1.

Clinical photograph showing the presentation of the AM prior to excision. a The lesion, located at the sternal cicatrix following coronary artery bypass grafting (CABG), lacks pigmentation and exhibits an atypical appearance of melanoma. b Clinical photograph of the cicatrix 1 month after complete removal of the melanoma with the initial excisional biopsy. c Clinical photograph taken 2 weeks after re-excision to a 2 cm margin and reconstruction of the defect using bilateral hatchet flaps. d Clinical photograph 1 year and 4 months after the re-excision and reconstruction and 3 months after end treatment with pembrolizumab, showing a satisfactory esthetic outcome and no signs of recurrence.

Fig. 2.

a Histological sections through skin excision showing large tumor with ulcerated surface epithelium. b Higher magnification shows spindle-shaped tumor cells with pleomorphic and elongated nuclei, while in other areas, they are more rounded. The cytoplasm is abundantly light eosinophilic with no pigmentation. Numerous mitoses are present in the tumor tissue, including several abnormal ones. c Immunohistochemically, there is loss of Melan-A except for normally appearing single-layered melanocytes located basally in the reactive epithelium. d The tumor cells are positive for S-100, SOX10 (not shown), and PRAME.