Primary hepatic melanoma in child: a case report and literature review

Clinical History

A 12-year-old male patient presented a 2-year history of upper abdominal pain.
Physical examination found no palpable lymph nodes or pigmented patches. Abdomen was soft with no tenderness and no palpable liver. Liver percussion pain was positive. Liver function tests revealed that globulin was 18.7 g/L. Tumour markers of AFP and CEA were normal.

Imaging Findings

B-mode showed a 6.2cm×4.2cm high-echo nodule with low-echo area in the right-posterior lobe of the enlarged liver (Fig. 1). CT displayed a 6.0cm×4.2cm low-density lesion with central high-density area (Fig. 2). On arterial phase (Fig. 3), the lesion showed heterogeneous enhancement with clear margin. On portal venous (Fig. 4) and delayed phase (Fig. 5), the lesion’s enhancement effect dropped off, especially on delayed phase, and the lesion’s density was adjacent to surrounded liver. We didn’t advise the patient to undergo MRI examination due to the consideration of partial hepatectomy.

Discussion

Primary hepatic melanoma (PHM) is a highly rare non-epithelial neoplasm which arises from melanocyte. Only 14 cases have been reported and most of PHM cases were prevalent in patient over the age of 30 years [1], and no case in a child. Due to the lack of information on this rare disease, a uniform diagnostic criterion for PHM has not been established up to now. However, Willis et al put forward three vital criterions for diagnosing PHM. The three criterions are as follows: histological and pathological appearance of PHM; no evidence for PHM originating from other sites; absence of unknown types of skin lesion and surgical history of the eye.
The patient underwent right partial hepatectomy and resection of the lymph nodes. Pathology revealed that tumorous growth was invasive along with internal necrosis and haemorrhage. Immunohistochemical examination demonstrated that the tumour cells were positive for HMB45, but negative for S-100. Exhaustive examinations of the body were performed and no other possible primary site of melanoma was detected after operation. Based on these results and diagnostic criterion mentioned above, the patient was diagnosed of PHM.
PHM express high-echo lesion within enlarged liver, though central low echoes or high density area in our case and reported literature [1, 2] is not clear, we assume it was probably due to internal necrosis and haemorrhage. CT enhancement effect recedes after artery phase, but contrast medium continues filling, leading to the enhancement variation of PHM presenting the characteristic of raising greatly and reducing slowly.
Hu X [3] proposes that MRI manifestation of PHM is characteristic with increased signal on T1WI and decreased signal on T2WI, but MRI performances in few cases do not coincide with the previous view according to literature review, such as mixed low-equal signal on T1WI and high signal on T2WI [4]. Some scholars think melanoma will create a paramagnetic material which can shorten T1 and T2 relaxation time, causing PHM to present a typical signal. However, when melanomas have less melanin deposition with internal haemorrhage and necrosis, their MRI manifestation is untypical, in that condition, it will be more difficult to diagnose PHM from the perspective of medical radiology.

Differential Diagnosis List

Final Diagnosis

Primary hepatic melanoma

URL:	https://www.eurorad.org/case/13660
DOI:	10.1594/EURORAD/CASE.13660
ISSN:	1563-4086