Melanoma is currently the fifth most common cancer in the United States (US) and most often develop on areas that have increased sun exposure, such as the arms, legs, back or face. The incidence of primary cutaneous melanoma increases each year and curative treatment improves with earlier detection of disease. Primary cutaneous umbilical melanoma is extremely rare with as few as 46 cases reported worldwide. As a result, limited literature is available regarding the management of tumors originating in the umbilicus. By evaluating uncommon areas such as the umbilicus, earlier detection and possible intervention can be provided. We present a rare case of a 33-year-old female with a primary cutaneous melanoma of the umbilicus successfully treated with wide local excision (WLE) and sentinel lymph node biopsy (SLNB).

Primary umbilical melanoma is rare tumor, representing about 5% of all umbilical malignancies.The lymphatic drainage from the tumor is challenging and can be to inguinal, axillary and retroperitoneal nodes. Dynamic and static lymphoscintigraphy with single-photon emission tomography/computed tomography (SPECT/CT) and sentinel lymph node biopsy (SLNB) is a widely validated technique in patients with clinically localized melanoma to search for and quantify nodal spread of cutaneous melanoma. Moreover, it offers the surgeon the preoperative information about the number and location of the sentinel lymph nodes (SLNs), which makes SLNB easier and quicker. This is the first report of an ulcerated thick melanoma of the umbilicus metastasizing only to an external iliac lymph-node without involvement of superficial inguinal SLNs. The preoperative high-resolution ultrasound (HR-US) examination of the regional lymph node field had been normal. This case-report shows how addition of SPECT/CT to planar imaging in a patient with clinically localized umbilical melanoma can help avoid incomplete SLNB when a deep SLN is not removed. A literature review of umbilical melanoma is also provided.

Umbilical melanoma is extremely rare. Among the past English reports on umbilical melanoma, there are only 8 reports in which histopathology was described in detail, and there has been no report with a review of the histopathology of previously reported cases. We experienced a case of umbilical melanoma and reviewed previously reported cases including our case. Because of the anatomical location, it is difficult to become aware of the umbilical melanoma unless there are some concomitant symptoms such as discharge or swelling. Even with these symptoms, patients tend to postpone a hospital visit for unknown reasons, resulting in increased risk of tumor growth and metastasis. When performing resection of umbilical melanoma, a portion of the peritoneum should also be removed. Sentinel lymph nodes can be axilla or inguinal lymph nodes. There is a possibility of metastasis to the preoperative abdominal cavity or to nearby skin through hematogenous spread. Preoperative evaluation of tumor spread and postoperative observation are important for umbilical melanoma in order to detect recurrence or metastasis because of its unique anatomical location.