Partial hepatectomy for primary hepatic melanoma: a report of two cases and review of the literature

Report on a case of liver-originating malignant melanoma of unknown primary

Malignant melanoma (MM) frequently occurs in the skin or mucosa, whereas malignant melanoma of unknown primary (MUP) is diagnosed in patients with lymph nodes or visceral organs as the site of origin, where it is challenging to detect the primary lesion by comprehensive examination. MUP is possibly related to the spontaneous regression of the primary lesion. In addition, primary hepatic melanoma (PHM) usually refers to the primary MM occurring in the liver, with no typical primary lesions and no manifestations of tumor metastasis. A 61-year-old male patient with liver as the site of origin was diagnosed with MM by Melan-A, HMB-45, and S-100 immunohistochemistry staining of liver biopsy tissue. Based on a comprehensive examination, no basis was found for melanoma in sites such as the skin, mucosa, five sense organs, brain, digestive tract, respiratory tract, or genitalia, and the patient was subsequently diagnosed with MUP. MMs require a comprehensive inspection, beginning with the liver, to search for the primary lesion; if the primary lesion is not found, the possibility of PHM or MUP should be considered.

[Primary liver melanoma: about a case]

Le mélanome malin est une maladie à fort potentiel métastatique qui se développe aux dépens des mélanocytes. Le foie est l´organe le plus souvent concerné par les métastases. Néanmoins le mélanome hépatique primitif est très rare. Peu de cas de mélanomes hépatiques primitifs ont été décrits. Nous rapportons le cas d'une patiente atteinte de mélanome hépatique primitif qui a été diagnostiquée par ponction biopsie hépatique, confirmé histologiquement et immuno-histochimiquement, avec une évaluation complète qui a permis d´exclure les autres mélanomes primitifs.

Primary Heptaic Melanoma or Melanoma of Unknown Primary?

Melanoma is the deadliest malignancy of the skin with an estimated 91 000 new annual cases with 9300 deaths in 2018. Metastatic disease generally presents with identification of known primary lesion; however, in 3.2% of patients, metastatic disease is discovered with unknown primary lesion/site. Rarely, melanoma is diagnosed as a primary lesion in visceral organs. Suspected primary hepatic melanoma is exceedingly rare and described in only a few case reports. We present the case of a 69-year-old Caucasian male who was found to have a hepatic melanoma on final pathology after resection of suspected primary hepatic malignancy. After a thorough postoperative workup, a primary lesion was unable to be identified. As such, a visceral primary lesion is considered.

Primary hepatic melanoma: A case report of computed tomography and magnetic resonance imaging findings

RATIONALE

Malignant melanoma predominantly develops in middle-aged and older adults, most commonly occurring on the skin and rarely on internal organs. Malignant melanoma originating in the liver is extremely rare. Imaging findings of primary hepatic melanoma (PHM) are scarce in relevant literature.

PATIENT CONCERNS

The patient was a 69-year-old woman from Zhejiang, China, who was admitted to the hospital because of upper abdominal pain that persisted for >10 days.

DIAGNOSES

Computed tomography (CT) findings indicated the presence of a circular low-density shadow of approximately 7.5 × 8.0 cm in the hepatic hilar region. Magnetic resonance imaging (MRI) indicated a heterogeneous solid cystic mass in the hepatic hilar region. The mass exhibited heterogeneous low-signal intensity on a T1-weighted image (T1WI) and slightly higher signal intensity on a T2-weighted image (T2WI). The tumor appeared as multiple irregular strips with high-signal intensity on T1WI and low-signal intensity on T2WI. The diffusion-weighted image revealed increased signal intensity. The tumor continued to be enhanced after enhancement. Clinical data suggested that the tumor was a malignant liver tumor.

INTERVENTIONS

The patient underwent a CT guide puncture hepatic biopsy. The tumor was located in the hepatic hilar region adjacent to the large blood vessels and invaded the portal vein. Because a resection was highly risky, conservative treatment was conducted.

OUTCOMES

Postoperative pathology and clinical examination confirmed that the tumor was malignant PHM. The patient has been followed up for 6 months. The patient underwent CT reexamination 2 months after conservative treatment, the results of which revealed that the tumor progressed. Multiple lesions were identified; moreover, the tumor size had increased and the tumor had invaded the portal vein and intrahepatic bile duct. The patient was reexamined by CT in another hospital 6 months after conservative treatment. The results revealed peritoneal, omental metastases and multi bone metastases.

LESSONS

To our best knowledge, this is the first reported case of a PHM with complete imaging data, including preoperative CT and MRI examinations and a follow-up CT examination. From compiling the CT and MRI findings of this patient and those of relevant studies, this study can serve as a reference for the preoperative diagnosis and differential diagnosis of PHM.