Fine needle aspiration biopsy diagnosis of a gastrointestinal stromal tumor utilizing transmission electron microscopy

BACKGROUND: Gastrointestinal stromal tumors are spindle cell tumors with no specific cell lineage occurring in the gastrointestinal tract and cytologically resemble other benign and malignant spindle cell tumors. Distinctive ultrastructural features in some of these tumors have not been previously emphasized. CASE: A 76-year-old, white female presented with multiple tumor masses distributed in the large bowel. Fine needle aspiration biopsy demonstrated a cellular aspirate composed of spindle cells, some of which were loosely arrayed and some of which were in cohesive clusters. Many of the cells contained long cytoplasmic processes. Ultrastructurally the cells demonstrated long cytoplasmic processes upon which multiple shorter, fingerlike projections arose. Subsequent surgical resection confirmed the cytologic and ultrastructural findings. CONCLUSION: Electron microscopy has a role to play in the diagnosis of gastrointestinal stromal tumors.