The cells of benign and malignant hemangiopericytomas in aspiration biopsy

Samples obtained by fine‐needle biopsy of two benign and one malignant hemangiopericytoma revealed tumor cells with round, oval, or spindle‐shaped nuclei, with variable and ill‐defined filmy cytoplasm. The nuclei had a finely granular chromatin pattern with or without inconspicuous nucleoli. They were seen singly or in loose or dense cellular clusters. Focal gland‐like arrangement of tumor cells was noted in some cellular clusters. Benign endothelial cells were seen among tumor cells and were not cohesive to the latter. The benign and malignant nature of hemangiopericytoma cannot be predicted by examination of the cells present in the aspirates. Also, a specific diagnosis of hemangiopericytoma could not be made on cytologic basis alone as cells of hemangiopericytoma were difficult to differentiate from those of other spindle‐cell mesenchymal tumors.