This pathology video details the microscopic analysis of a complex vascular lesion, ultimately diagnosed as a Spindle Cell Hemangioma. The lesion exhibits a biphasic morphology, initially presenting with large, dilated "cavernous" vascular spaces containing organizing thrombi and calcified components known as phleboliths. The key diagnostic feature is the presence of a distinct cellular zone characterized by spindled endothelial cells, slit-like vascular channels, and pathognomonic endothelial vacuoles resembling tiny fat cells. The speaker clarifies that despite its potential for multifocality and recurrence, this is a truly benign vascular neoplasm, distinguishing it from intermediate-potential tumors. Finally, the lesion's association with Maffucci syndrome and its underlying molecular link to $IDH1/IDH2$ mutations are discussed, with confirmation that the specific case analyzed carried an $IDH1$ mutation.
0:44 Cavernous Spaces and Initial Diagnosis: The lesion is characterized by multiple big, dilated vascular spaces (cavernous spaces), leading to an initial differential diagnosis of Cavernous Hemangioma or benign vascular malformation.
1:09 Organizing Thrombus: Blood within the spaces is forming organizing thrombi (clots). Early stages of organization show perforation by small vessels, similar to the process seen in papillary endothelial hyperplasia (Massen tumor).
2:55 Calcification (Phleboliths): Calcification is noted within the thrombi. These "thrombus stones" or phleboliths are a specific finding that can sometimes be visible on X-rays.
3:22 Biphasic Morphology: The lesion is described as biphasic, featuring both large cavernous areas and a more cellular zone composed of spindled endothelial cells and compressed, slit-like vascular channels.
3:46 Differential Diagnosis Check: The cellular zone may superficially resemble Kaposi's Sarcoma, but the context (deep tissue rather than a primary dermal process) helps rule this out.
4:56 Key Diagnostic Feature (Vacuoles): The critical finding is the presence of endothelial vacuoles which appear similar to tiny fat cells—a striking resemblance characteristic of this entity.
5:30 Final Diagnosis: The combination of cavernous spaces, spindled cells, and characteristic vacuoles establishes the final diagnosis as Spindle Cell Hemangioma (formerly Spindle Cell Hemangioendothelioma).
5:38 Takeaway: Benign but Multifocal: Spindle Cell Hemangioma is a truly benign vascular neoplasm. However, it is noted for its tendency to be multifocal (occurring in the same region, sometimes arising inside veins) and can recur, but it is not aggressive (7:00).
7:12 Syndrome Association: The entity is related to Maffucci Syndrome, a rare condition caused by $IDH1$ or $IDH2$ mutations that results in multiple bone tumors (enchondromas) alongside vascular lesions.
8:15 Molecular Confirmation: Even in sporadic cases, $IDH1$ or $IDH2$ mutations are common. The video creator confirmed that this specific sample was mutated for $IDH1$.