This brief pathology video reviews a challenging case identified as Kaposi Sarcoma (KS), specifically focusing on its nodular or tumor stage presentation. The case is introduced as potentially being mistaken for a Pyogenic Granuloma due to its atypical but non-pleomorphic spindle cells arranged in fascicles. The video highlights the essential diagnostic features, including the presence of slit-like vascular spaces filled with blood and the characteristic "sieve" or "colander" pattern seen when the fascicles are cut in cross-section. The utility of the highly sensitive and specific HHV-8 immunostain for definitive confirmation is also emphasized.
Pathology Case Review: Identifying Kaposi Sarcoma (Tumor Stage)
0:18 Atypical Morphology: The lesion consists of spindly, plump, hyperchromatic cells running in fascicles, showing scattered mitosis but typically lacking widespread pleomorphism.
0:21 Initial Differential Diagnosis: The appearance might initially suggest a Pyogenic Granuloma (PG), but the spindle cell arrangement is key to differentiation.
0:48 Key Architectural Feature: The lesion shows slit-like spaces containing blood interspersed within the fascicles of atypical spindle cells.
0:57 Diagnosis: The features confirm Kaposi Sarcoma (KS), representing the nodular or tumor-type stage.
1:08 Sieve/Colander Pattern: When the fascicles of spindle cells are cut in cross-section, they exhibit small, blood-filled holes, resembling a sieve or spaghetti strainer—a reliable diagnostic feature.
1:23 Confirmatory Stain: If there is any doubt regarding the diagnosis, the HHV-8 stain should be performed, as it is highly sensitive and specific for Kaposi Sarcoma.
1:30 Key Takeaway: The combination of atypical spindle cells in fascicles and the characteristic slit-like or sieve-like vascular spaces confirms the tumor stage of Kaposi Sarcoma.