[Primary melanoma of the bladder. A case report]

Identification of distinct genomic features reveals frequent somatic AHNAK and PTEN mutations predominantly in primary malignant melanoma presenting in the ureter

BACKGROUND

Primary malignant melanoma of the ureter is extremely rare. Genetic variants to the increased risk of developing the disease have not yet been investigated.

METHODS

Tumour mutation profiling for primary malignant melanoma of the ureter was performed by whole-exome sequencing. Immunohistochemistry was performed to verify histopathological features and the variants of predisposing genes and driver mutation genes. Furthermore, we conducted a literature review and Surveillance, Epidemiology and End Result-based study by searching public databases.

RESULTS

We identified 38 somatic single nucleotide variants and 9 somatic insertions and deletions (INDELs) in tumour specimens. After filtering with the Cancer Gene Census database, seven predisposing genes and two driver mutation genes were identified. Moreover, the immunohistochemical profile showed that tumour cells were positive for Melan-A, melanoma gp100 human melanoma black 45 (HMB45), S100 beta and P53. The expression levels of two driver mutation genes (phosphatase and tensin homolog (PTEN) and desmoyokin (AHNAK) and five predisposing genes (AT-rich interaction domain 1B (ARID1B), catalase, eukaryotic translation initiation factor 4 gamma 3 (EIF4G3), ANK3 and collagen type I) were significantly downregulated in tumour tissues compared to paracancerous tissues. In the literature review and Surveillance, Epidemiology and End Results-based study, patients with primary malignant melanoma of the urinary tract had worse clinical outcomes than patients with primary urothelial carcinoma after 1:2 propensity score matching (P = 0.010). Additionally, Cox multivariate analysis for patients with primary malignant melanoma of the urinary tract indicated that distant metastasis (hazard ratio = 1.185; P = 0.044) was an independent predictor for overall survival, and tumour focality (hazard ratio = 0.602; P = 0.017) and non-surgery (hazard ratio = 0.434; P = 0.003) were independent factors for tumour progression.

CONCLUSIONS

Our study is the first to provide evidence that the distinct phenotypes of primary malignant melanoma of the ureter may be due to different genetic variations. The prognosis of primary malignant melanoma of the urinary tract was poorer than that of primary urothelial carcinoma of the urinary tract.

Primary Malignant Melanoma of the Bladder: A Rare Case Report in Asia and Review of the Literature

Background

Primary malignant melanoma (PMM) of the bladder is extremely rare and has a poor prognosis; just 40 cases of PMM of the bladder have been recorded in the literature. We described a case of PMM of the bladder, treatment, and a review of the literature because the recommended treatment choices are not widely known.

Case Presentation

An 80-year-old Thai female came in with a three-month history of pelvic pain and dysuria without extensive hematuria. She underwent transurethral excision of the bladder tumor and histologically reported malignant melanoma with no further primary sites of melanoma after computed tomography indicated a big heterogeneous enhancing mass on the posterior wall of the bladder. The patient eventually underwent anterior pelvic exenteration with ileal conduit, but metastatic disease occurred one year later.

Conclusion

Bladder melanoma has a fatal aggressive nature. Certain diagnostic features can be obtained through histopathological investigation, immunohistochemistry, clinical history, and endoscopic evaluation. Despite a wide range of treatments, people with PMM still have a bad prognosis.