Disseminated Melanoma With Rare Multiorgan Visceral Involvement in a Young Adult: A Case Report

ABSTRACT

Melanoma may present aggressively in young adults with widespread cutaneous lesions and early multiorgan visceral metastases, including rare involvement of the spleen, liver, gallbladder, kidney, urinary bladder, vertebra, and abdominal wall. Recognition of such atypical dissemination is essential for accurate diagnosis, staging, and consideration of molecular and genetic evaluation.

1. Introduction

Melanoma is an aggressive malignancy of melanocytes, with a steadily rising incidence, particularly in developed countries with lighter skin populations [1]. It represents 1.7% of global cancer cases, and the global burden of the disease increased in 2020 to 325,000 cases from 230,000 cases in 2012 [2, 3]. Metastatic melanoma carries a poor prognosis, particularly in patients with involvement of multiple organ systems [4]. Common metastatic sites include lymph nodes, lungs, liver, and brain, whereas visceral involvement of the spleen, urinary bladder, and ureter remains rare [5].

We report a young patient presenting initially with a nodular black cutaneous mass over the left chin, which was diagnosed as a benign naevus. However, he subsequently developed numerous cutaneous and subcutaneous nodules with involvement of multiple sites, including spleen, liver, ureter, urinary bladder, and vertebra within a span of two months. It was proven to be melanoma upon additional cytological and histopathological analysis.

2. Case History/Examination

A 25‐year‐old man presented with a history of rapidly developing multiple black cutaneous nodular masses as well as subcutaneous nodules over his neck, shoulders, back, and abdomen (Figures 1, 2). The lesions were progressive, non‐tender, variable in size, and the largest measured approximately 1.5 cm. The patient also reported abdominal pain and progressive blurring of vision. An initial lesion from the left chin had previously been diagnosed as a benign melanocytic nevus at an outside institution in another country. The original histopathology slides and paraffin blocks could not be retrieved for review; hence, reassessment of the initial diagnosis was not possible.

FIGURE 1.

Numerous varying sized pigmented cutaneous nodules over the back.

FIGURE 2.

Multiple subcutaneous nodules over neck.

3. Investigations and Treatment

MRI of the abdomen and pelvis demonstrated multiple T1/T1 fat‐suppressed‐hyperintense and T2‐hypointense lesions involving the spleen, segment VIII of the liver, gallbladder, right ureter, urinary bladder, lumbar vertebra, skin, subcutaneous tissue, as well as the muscular plane of the abdominal wall (Figures 3, 4). The largest lesion was seen in the spleen, measuring 2.3 × 2.2 cm. Based on imaging characteristics, a possibility of melanoma was suggested.

FIGURE 3.

Axial T1FS sequence demonstrating hyperintense lesions involving the spleen, lumbar vertebrae, gallbladder, and posterior abdominal wall.

FIGURE 4.

Axial T1‐weighted image showing a hyperintense polypoidal lesion arising from the right antero‐lateral wall of the urinary bladder.

Ultrasound‐guided FNAC from a splenic lesion yielded a dark brown aspirate. Cytology revealed a highly cellular tumor composed of predominantly epithelioid cells with abundant cytoplasm, pleomorphic nuclei, prominent nucleoli, and intracytoplasmic melanin pigment. Occasional atypical mitoses were noted (Figure 5). A few atypical mitotic figures were also noted. These findings favored the diagnosis of splenic involvement by melanoma. Excisional biopsy from a shoulder nodule showed asymmetrically infiltrative tumor cells with marked nuclear pleomorphism (Figure 6).

FIGURE 5.

Pap stain, 400×: FNAC Splenic lesion aspirate showing dyscohesive polygonal tumor cells with prominent nucleoli, extensive cytoplasmic melanin pigments, and few mitotic figures.

FIGURE 6.

H&E stain, 400×: Biopsy of the shoulder nodule showing atypical melanocytes with marked nuclear pleomorphism.

The patient was initiated on combination therapy with nivolumab and dacarbazine administered intravenously at 2‐week intervals, considering the aggressive clinical course and high tumor burden.

4. Follow‐up and Outcome

The patient has shown clinical stability with no development of new cutaneous or subcutaneous lesions. He is currently maintained on nivolumab therapy and is tolerating treatment well without significant adverse effects.

Regular clinical follow‐up is ongoing, with monitoring for disease progression and treatment‐related toxicity. A follow‐up PET‐CT scan is planned after 6 months of therapy to assess treatment response and guide further management. Long‐term surveillance with periodic imaging has been advised.

5. Discussion

Melanoma is known for its ability to metastasize widely. The most frequent sites of metastasis are nearby skin, lymph nodes, and subcutaneous tissue [6]. The present case also had multiple cutaneous and subcutaneous lesions, along with clinically detected axillary lymphadenopathies. An autopsy series of 216 patients with advanced malignant melanoma demonstrated 95% of cases having multiorgan metastasis. Common sites of metastases were lymph nodes, lung, liver, brain, and bone in that order [7]. Consistent with these findings, our patient showed lesions in the liver, spleen, genitourinary tract, and gallbladder. Lung and brain imaging were not performed. It should be noted that the involvement of the vertebral body by melanoma seen in this case is rare, observed in only 2.4% of cases as per previous literature [8]. Our case had rapid progression of melanoma with widespread metastasis similar to a case reported by Erkurt et al. where the patient developed multiple metastases from nodular melanoma within a span of 2 months [9].

MRI is frequently used to determine the location and size of melanoma metastasis. The metastatic lesions are T1 hyperintense and T2 hypointense which is consistent with the MRI finding in the present case [10] However, these findings are not specific and tissue diagnosis remains the “gold standard” for diagnosing melanoma [11]. Comprehensive staging, including evaluation of the lungs and brain, is critical in metastatic melanoma. In this case, such imaging wasn't performed, although follow‐up PET‐CT had been planned to address this gap.

Our case had been earlier diagnosed as a deep penetrating nevus (DPN) on a wedge biopsy from the left chin nodule. Melanoma can mimic DPN and vice versa on dermatopathological examination [12]. In melanoma, atypical melanocytes arise at the dermo–epidermal junction and infiltrate the dermis in an irregular and destructive manner. In contrast, DPN shows a minimal junctional component with preservation of dermal collagen and adnexal structures. Features favoring melanoma include frequent mitoses, marked cytologic atypia, epithelioid cells with scant pigment, solid growth, reactive stroma, and accompanying plasma cells [13]. This distinction is clinically important, as excisional biopsy is sufficient for DPN, whereas melanoma requires multimodal approaches including surgical resection, chemotherapy, photodynamic therapy, immunotherapy and targeted therapy [14, 15].

Nivolumab has been shown to be effective and well tolerated in patients with metastatic melanoma [16]. The addition of Dacarbazine, although not standard in current guidelines, may be considered in selected cases with aggressive disease. Chemotherapy‐induced tumor cell death may enhance antigen release, potentially augmenting immune response, while Nivolumab restores T‐cell activity. Our patient has also been instituted this immunotherapy and is responding well with no additional increase in existing lesions or appearance of new lesions. However, only 2 months have elapsed since the initiation of treatment, and a follow‐up PET CT is planned to assess response after 6 months. In patients with Stage IV disease like our case, the prognosis remains poor, with a study by Sandru et al. demonstrating a median overall survival of only 5.3 months [17]. With current multimodal therapies, studies have shown the 5 ‐year overall survival approximating 33% even in metastatic melanomas [18].

It is worth stressing that in a young patient like ours presenting with disseminated melanoma, an underlying genetic predisposition should be considered. Familial Atypical Multiple Mole Melanoma (FAMMM) syndrome, an autosomal dominant condition most commonly associated with CDKN2A mutations, is characterized by early‐onset melanoma and multiple atypical nevi. Although genetic testing and detailed family history may not always be available, awareness of FAMMM syndrome is important, as its recognition has implications for patient counseling, surveillance of at‐risk relatives, and long‐term follow‐up. Molecular profiling, particularly assessment of BRAF mutation status, is also essential in modern melanoma management as it enables the use of targeted therapies. In the present case, molecular testing could not be performed due to resource limitations, representing an additional constraint in optimizing therapy [19, 20].

6. Conclusion

This case highlights the aggressive nature of melanoma in young adults and its potential for rapid dissemination to uncommon visceral and skeletal sites. The initial misdiagnosis as a benign melanocytic lesion underscores the importance of careful histopathological evaluation and clinicoradiological correlation in atypical or rapidly progressive lesions. Awareness of rare metastatic patterns and close follow‐up are crucial for early diagnosis and timely initiation of appropriate therapy. Although disseminated melanoma carries a poor prognosis, advances in immunotherapy might offer meaningful disease control and improved outcomes. An underlying genetic predisposition should be considered in young patients with widespread disease.

Author Contributions

Oshan Shrestha: conceptualization, investigation, supervision, writing – original draft. Neha Shrestha: investigation, methodology, validation. Unisha Karki: data curation, methodology, resources, validation. Saurav Kumar Jha: formal analysis, investigation, resources.

Funding

The authors have nothing to report.

Ethics Statement

The authors have nothing to report.

Consent

Written informed consent was obtained from the patient for publication of this case report and any accompanying images in accordance with the journal's patient consent policy.

Conflicts of Interest

The authors declare no conflicts of interest.

Data Availability Statement

The data supporting the findings of this case report are included within the article. Further details are available from the corresponding author upon reasonable request.