Pheochromocytoma of the adrenal gland scaled score (PASS) as a predictor of aggressive biologic behaviour
María Riestra Fernández, Pedro Boix Pallarés, Edelmiro Menéndez Torre, Cecilia Sánchez Ragnarsson, Javier Aller Granda, Antonio Rabal Artal, Elías Delgado Álvarez, Antonio Lavilla Corcovado, Joaquin Petierra de la Uz, Marta Dieguz Felechosa & Virginia Bellido Castaneda
Background: Up to 15% of pheochromocytomas are malignant. The only definite criterion for malignancy is the presence of metastases. The histological differentiation between benign and malignant tumours is difficult, being a challenging problem nowadays.
Aim: To asses if postoperative histological evaluation using the previously proposed pheochromocytoma of the adrenal gland scales scored (PASS) can predict malignancy.
Methods: Twenty-nine pheochromocytomas have been retrieved from 1985 to 2009. A single pathologist, blinded to clinical outcome, reviewed the histopathologic characteristics of all cases using the PASS system. This score includes 12 different features, for instance tumour necrosis, mitotic rate, tumour cell spindling or the presence of large cell nests. It has been suggested that a score ≥4 can be used to separate tumours with aggressive potencial behaviour.
Results: Twenty-six patients had a benign outcome while three had a clinically malignant pheochromocytoma. The mean PASS score punctuation in benign tumours was eight, whereas in malignant tumors it was 8.3. None of the histopathologic features included in the PASS system was present in the 100% of the malignant tumours. None of the benign pheochromocytomas obtained a PASS <4. 38% of the benign tumours had a score ≥9, compared with the 68% of the malignant pheochromocytomas.
Conclusions: In our experience, the PASS system does not appear to have a major role in predicting the behaviour of pheochromocytomas. We consequently suggest that PASS requires further refinement and validation, before it can be recommended as a valuable tool for clinical prognostication.