Location
Moultrie, GA
Start Date
17-4-2026 12:00 PM
End Date
17-4-2026 1:00 PM
Description
Introduction: Melanoma of Unknown Primary (MUP) presents a significant clinical challenge in tracing metastatic trajectories. While hematogenous dissemination is the traditional model, this study investigates angiotropism and perineural invasion—mechanisms where neoplastic cells migrate along the external surfaces of anatomical structures. Our research suggests that melanoma acts as a "hitchhiker," utilizing the adventitia of blood vessels and the epineurium of nerves as a private highway system. This study aims to provide a high-resolution, whole-body map of infiltration, documenting how these "extravascular conduits" facilitate the colonization of major organ systems. Methods: A high-resolution post-mortem mapping was performed on a 50-year-old male decedent with disseminated Stage IV MUP. A systematic harvest of over 35 anatomical checkpoints was conducted, spanning the head, eyes, nose, thoracic, abdominal, and pelvic cavities. The protocol involved a comprehensive sampling of both organ parenchyma (lungs, liver, kidneys, spleen, pancreas, colon, adrenal glands) and neurovascular bundles (superior mesenteric artery (SMA), celiac ganglion, sciatic nerve, and optic chiasm). Tissues were analyzed via H&E staining to log the extent of tissue destruction and differentiate between traditional intravascular seeding and extravascular migration. Results: Histological analysis confirms a dense, pan-systemic distribution of the disease. High-volume malignancy was logged in various organ parenchyma, including the pulmonary apex, hepatic sinusoids, and the adrenal glands. Ongoing histopathological analysis continues to refine the map; however, initial findings identify pleomorphic, hyperchromatic malignant cells encasing the perivascular tissue of the SMA. Additionally, the kidney shows glomerular atrophy and tubular sclerosis, consistent with chronic ischemic changes secondary to compromised systemic perfusion associated with advanced metastatic disease. Conversely, reactive lymphocytosis in multiple lymph node basins identifies the immunological "frontiers" where the host response attempted to arrest tumor progression. Conclusion: These findings support the theory that melanoma utilizes perivascular and perineural niches as continuous "anatomical highways" for systemic spread. The presence of malignant cells within the SMA bundle provides a model of extravascular migratory metastasis (EVMM), allowing the cancer to bypass traditional capillary filters and reach "sanctuary organs" such as the brain. This "crawling" mechanism on the vasa vasorum and neural sheaths explains the aggressive, non-linear distribution characteristic of MUP. By documenting the connectivity between pulmonary exit points and abdominal arterial hubs, this study offers a high-resolution framework for understanding the systemic high-jacking of the body’s internal infrastructure. These findings suggest that diagnostic screening for MUP should prioritize imaging of high-risk neurovascular hubs, such as the SMA-celiac junction, to identify early-stage extravascular migration before systemic spread occurs.
Embargo Period
5-26-2026
Included in
Whole-body anatomical mapping of infiltration in melanoma of unknown primary (MUP): The role of perivascular, lymphatic, and neurovascular conduits
Moultrie, GA
Introduction: Melanoma of Unknown Primary (MUP) presents a significant clinical challenge in tracing metastatic trajectories. While hematogenous dissemination is the traditional model, this study investigates angiotropism and perineural invasion—mechanisms where neoplastic cells migrate along the external surfaces of anatomical structures. Our research suggests that melanoma acts as a "hitchhiker," utilizing the adventitia of blood vessels and the epineurium of nerves as a private highway system. This study aims to provide a high-resolution, whole-body map of infiltration, documenting how these "extravascular conduits" facilitate the colonization of major organ systems. Methods: A high-resolution post-mortem mapping was performed on a 50-year-old male decedent with disseminated Stage IV MUP. A systematic harvest of over 35 anatomical checkpoints was conducted, spanning the head, eyes, nose, thoracic, abdominal, and pelvic cavities. The protocol involved a comprehensive sampling of both organ parenchyma (lungs, liver, kidneys, spleen, pancreas, colon, adrenal glands) and neurovascular bundles (superior mesenteric artery (SMA), celiac ganglion, sciatic nerve, and optic chiasm). Tissues were analyzed via H&E staining to log the extent of tissue destruction and differentiate between traditional intravascular seeding and extravascular migration. Results: Histological analysis confirms a dense, pan-systemic distribution of the disease. High-volume malignancy was logged in various organ parenchyma, including the pulmonary apex, hepatic sinusoids, and the adrenal glands. Ongoing histopathological analysis continues to refine the map; however, initial findings identify pleomorphic, hyperchromatic malignant cells encasing the perivascular tissue of the SMA. Additionally, the kidney shows glomerular atrophy and tubular sclerosis, consistent with chronic ischemic changes secondary to compromised systemic perfusion associated with advanced metastatic disease. Conversely, reactive lymphocytosis in multiple lymph node basins identifies the immunological "frontiers" where the host response attempted to arrest tumor progression. Conclusion: These findings support the theory that melanoma utilizes perivascular and perineural niches as continuous "anatomical highways" for systemic spread. The presence of malignant cells within the SMA bundle provides a model of extravascular migratory metastasis (EVMM), allowing the cancer to bypass traditional capillary filters and reach "sanctuary organs" such as the brain. This "crawling" mechanism on the vasa vasorum and neural sheaths explains the aggressive, non-linear distribution characteristic of MUP. By documenting the connectivity between pulmonary exit points and abdominal arterial hubs, this study offers a high-resolution framework for understanding the systemic high-jacking of the body’s internal infrastructure. These findings suggest that diagnostic screening for MUP should prioritize imaging of high-risk neurovascular hubs, such as the SMA-celiac junction, to identify early-stage extravascular migration before systemic spread occurs.
Comments
Winner of 2026 PCOM SGA Research Day Best in Show Award.