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Melanoma is one of the most aggressive forms of skin cancer. While most melanomas have a discernible primary site, a small subset, approximately 3.2%, present as a metastatic disease without an identifiable primary origin, a condition known as melanoma of unknown primary (MUP). Unusual cases of primary melanoma have also been previously reported in the respiratory, gastrointestinal, and urogenital tracts. MUP typically is found in lymph nodes, subcutaneous sites, and visceral organs, with hypotheses about its origin including spontaneous primary tumor regression and ectopic melanocytes. MUP presents unique challenges in diagnosis and treatment due to the absence of a detectable primary tumor. Understanding its genetic and molecular features, epidemiology, prognostic factors, and treatment options is crucial for optimizing patient care and outcomes in this subset of melanoma patients. We conducted an extensive literature review triggered by a case report of a patient with suspected MUP. A 51-year-old woman was transferred from another hospital where an incision was performed for a suspected superinfected hematoma of the left thigh. Since the patient showed high leukocytosis and redness and swelling of the thigh, local debridement, drainage, and excisional biopsy of the tumor mass were performed in our unit in the emergency setting, and the tumor was taken for histopathology evaluation. Intraoperatively, the mass appeared nonspecific. The permanent histopathology report established a diagnosis of melanoma, with tumor proliferation also involving lymphoid tissue, and despite broad clinical and imagistic assessments, the primary melanoma could not be identified. Clinicians must be aware of the varied clinical manifestations of malignant melanoma, especially in cases of occult melanoma where the primary site is not evident. [ABSTRACT FROM AUTHOR]

Background: Lung cancer, particularly small-cell lung carcinoma (SCLC), often presents with respiratory symptoms. However, atypical manifestations including jaundice and abdominal pain can obscure the diagnosis, leading to challenges in early detection and treatment. Case Presentation: A 49-year-old male, with a history of smoking and diagnosed with Chronic Obstructive Pulmonary Disease (COPD), presented to the emergency department with a 3-day history of jaundice and a 3-week duration of mild abdominal pain. Initial investigations, including blood tests, showed hyperbilirubinemia and elevated lipase and amylase levels. An abdominal ultrasound was performed and revealed a hypoechoic, inhomogeneous mass in the head of the pancreas and multiple liver masses, suggesting a cephalo-pancreatic formation with liver metastasis. Further diagnostic procedures, including upper endoscopy and ERCP, followed by a TAP CT scan, identified a large mediastinal-pulmonary mass with invasion into major vessels and extensive metastasis. The immunohistochemical analysis of a duodenal ulcer biopsy confirmed a diagnosis of duodenal metastasis from a small-cell neuroendocrine lung carcinoma. Conclusion: Our case highlights that while rare, the possibility of metastatic spread should be included in the differential diagnosis when obstructive jaundice occurs in the context of high-risk factors for lung cancer. [ABSTRACT FROM AUTHOR]