[Giant gastric stromal tumor simulating a focal hepatic lesion]. / Tumor estromal gástrico gigante simulando lesión ocupacional hepática.

Gastrointestinal stromal tumors (GIST), are unusual malignancies regarded for many years as being basically of smooth muscle nature and designated as leiomyomas, leiomyosarcomas or leiomyoblastomas. Histogenesis has been debated, though it is presently accepted that they are characterized by poorly differentiated cells, including tumors showing differentiation towards smooth muscle, neural elements, dual differentiation or lack of differentiation. Another group with ultrastructural and immunohistochemical features similar to those of gastrointestinal autonomic plexus has been described and designated as GAN tumors. Diagnosis and classification of these tumors are not possible using conventional pathological techniques, making ultrastructural and immunohistochemical studies necessary. Accurate classification is clinically essential due to prognostic implications. GIST present with few clinical symptoms even in cases of large tumors and are quite often incidentally found during surgical procedures or in postmortem studies. We report a case of a giant gastric stromal tumor showing differentiation towards smooth muscle which presented as a focal hepatic lesion.