Abstract:
Soft tissue tumours (STT) are relatively rare compared to other tumours and they have a wide variety of histological patterns and many entities with overlapping features. As a result, a significant proportion of STT are difficult to diagnose and to classify as benign or malignant.

It is important for pathologists to be aware of the diagnostic pitfalls as the implications of an erroneous diagnosis can be serious for the patient, the clinicians (including pathologists) and the responsible organisations. This presentation will seek to highlight benign lesions which mimic sarcomas, non-mesenchymal tumours that are often misdiagnosed as sarcomas, low grade tumours that are mistaken for high grade tumours and sarcomas that are often misclassified.

There are any number of diagnostic pitfalls in the gastro-intestinal (GI) tract but this presentation will concentrate on those that mimic malignancy. Indeed, one could make an argument that reactive conditions mimicking dysplasia are as common and cause as many problems. For instance, high grade dysplasia in the oesophagus may be an indication for oesophagectomy, an operation which, even in the best hands, has a mortality of up to 5%. The implications of an erroneous pathological diagnosis are obvious.

It behoves pathologists to be aware of the implications of their diagnoses. If the implication of a diagnosis is major surgery, then pathologists need to ensure that they recognise mimics of malignancy. Certainly, in the UK, it would seem that surgeons only need a “ticket to ride” and that, often, pathological diagnoses that do not correlate with clinical features may not be questioned. Added to this, there is an ever-burgeoning litigious community and erroneous diagnoses can be very expensive for responsible organisations.

Whilst there are any numbers of situations where there is mimicry of malignancy in the gut, this presentation will concentrate on four. This pathologist would particularly applaud the contribution, to the early literature, of Professor Peter Isaacson. Now much better known as one of the world’s top lymphoma pathologists, he produced the most insightful paper, back in 1982, concerning biopsy appearances that may be mistaken for malignancy in GI pathology, citing the advent of endoscopic biopsy as a major reason why pathologists might err in the diagnosis of malignancy. More than 40 years later, this pathologist sees any number of cases, in national and international practice, where erroneous diagnoses of malignancy have been made because of mimicry of malignancy by benign conditions. The lecture will discuss four such pitfalls and indicate ways how such misdiagnoses can be avoided.