55-year-old male, tumour on upper arm. Biopsy.
- Bundles of long, cytoplasm-rich spindle cells with distinct cell borders.
- Elongated, often rounded nuclei. Paranuclear vacuoles (containing glycogen). Mild to extensive cellular and nuclear polymorphism. Numerous mitoses.
- The intercellular substance consists of collagenous fibres with varying degree of collagenisation.
This is a commonly occurring soft tissue sarcoma (up to 20%) and can be distinguished from other spindle-cell shaped sarcomas by morphological characteristics as well as immunohistochemical stains (positive for smooth muscle alpha-actin, collagen IV). May occur as grade I to grade III sarcoma.