Giant lung metastasis of NRAS-mutant melanoma in a 24-year-old patient with a history of BRAF-mutant conventional melanoma harboring Spitzoid morphology: a case report
Authors: Vachtenheim Jiri , Kodet Roman , Fischer Ondrej , Kolek Vitezslav , Strizova Zuzana , Ozaniak Andrej , Simonek Jan , Stolz Alan , Pozniak Jiri , Kolarik Jan , Svorcova Monika , Vachtenheim Jiri , Lischke Robert 
Published: October 2020

Abstract
Background
Spitzoid melanocytic lesions represent a heterogeneous group of proliferations with ambiguous and overlapping terminology. The exact distinction of a Spitz nevus from a Spitzoid melanoma can be very difficult or, in some cases, impossible. Among the Spitzoid lesions, there is a lesion termed an atypical Spitz tumour (AST) that has intermediate histopathologic features between those of a Spitz nevus and a Spitzoid melanoma and thus uncertain malignant potential. There are several rare cases of patients with a Spitzoid melanoma initially misdiagnosed as a Spitz nevus or an AST with fatal consequences. It is, therefore, advised to perform a molecular characterization in cases where uncertain skin lesions are presented, as it may provide extended set of information with a possible impact on the treatment options. Furthermore, preventive measures, such as regular physical and skin examinations, as well as thorough scheduling of individual follow-up visits, are essential in patients with potentially malignant skin nevi.

Case report
We report a case of a young adult female with a history of AST excision with a negative sentinel lymph node biopsy (SLNB) and insufficient follow-up. Four years after the primary dermatological diagnosis, she presented with a giant tumour in the right hemithorax. Radical en bloc resection of the tumour with right pneumonectomy and resection of the pericardium with reconstruction of the pericardium using mesh was performed. A definitive histopathological examination revealed a metastatic melanoma. The association of the previously diagnosed AST and subsequent appearance of melanoma metastases led to a retrospective re-evaluation of the initial lesion. The suspected diagnosis of Spitzoid melanoma, however, was not confirmed. Moreover, the molecular examination revealed a major discordance between the initial lesion and the lung tumour, which most likely excluded the possible association of the lung metastasis with the initial skin lesion. The initial skin lesion was a BRAF-mutant melanoma with Spitzoid features and termed as AST, while the giant lung metastasis was NRAS-mutant melanoma. The subsequent postoperative course was complicated by the appearance of brain metastases that were stereotactically irradiated. Nevertheless, despite complex specialised medical care, the patient’s clinical condition rapidly deteriorated. By this time, no active oncological treatment was possible. The patient was delegated to local hospice for palliative care six months after the surgery and died three weeks later.

Conclusions
Our patient was surgically treated at the age of 20 for AST and died four years later of metastatic NRAS-mutant melanoma most likely of different occult origin. Molecular characterization, as well as the close clinical follow-up should be always precisely performed in patients with uncertain skin lesions, such as AST.