CD34 and leiomyosarcoma: Immunohistochemistry remains the cornerstone for accurate diagnosis, as leiomyosarcomas are almost always diffusely positive for α-SMA and variably positive for desmin, but typically negative for CD117 (c-KIT) and DOG1, which are key markers for diagnosing GISTs [6,7,10,11]. CD34 is typically positive in gastric GISTs, as it is present in over 90% of cases, its absence can help in distinguishing other mesenchymal tumors.