Metastatic tumours

[8,11] are normal. Considering the small volume of tissue sampled, both bone marrow aspiration and trephine biopsy are relatively sensitive techniques for detecting bone marrow infiltration by metastatic tumours. In two autopsy studies which simulated biopsy procedures, it was estimated that, when osseous metastases were present, a bone marrow aspirate would give positive results in 28% of cases [12] and a single trephine biopsy in 35–45% [13]. Trephine biopsy is more sensitive than bone marrow aspiration and sensitivity is increased by performing bilateral biopsies or by obtaining a single large biopsy. The sensitivity of aspiration is increased if large numbers of films are examined and if a clot section is also examined. It is common for tumour cells to be detectable in trephine biopsy sections when none are demonstrable in films of an aspirate [8,14]. Overall, about three quarters of metastases detected by a trephine biopsy are also detected by simultaneous bone marrow aspirate. Discrepancy between biopsy and aspirate findings usually results from a desmoplastic stromal reaction to the tumour which renders neoplastic cells more difficult to aspirate than residual haemopoietic cells. It is also, to some degree, a consequence of the different volumes of tissue sampled. Because of its greater sensitivity, trephine biopsy should always be performed when metastatic malignancy is suspected. However, tumour cells are seen occasionally in aspirate films when trephine biopsy sections appear normal [2,8,14] and the two procedures should therefore be regarded as complementary. Increasingly, bone marrow aspiration and trephine biopsy are being performed as staging procedures at the time of diagnosis in a number of solid tumours, principally neuroblastoma in children and TEN