Introduction

Histopathology plays an essential role in oncology, both in the initial tissue diagnosis of the tumour and later in the detailed examination of the surgical specimen. The information gained from the macroscopic and microscopic examination of the specimen will guide further treatment and establish prognostic and predictive markers for the patient. Pathologists will often demonstrate the morphology of tumours to the members of the multidisciplinary team (MDT). This is an excellent opportunity to question the pathologist on morphological descriptions and it provides a teaching experience for medical students through to senior consultants. Mutual understanding of working practices and interpretation of results among all members of the MDT improves team working and patient care.

Immunohistochemistry has revolutionised histopathology over the last 20–30 years and a number of tumours now require immunohistochemistry for their accurate diagnosis or subclassification. It has also, along with cytogenetics, significantly changed the analysis of lymphoreticular tumours with the REAL classification, which was adopted by the WHO and published in 2001 and updated in 2008 (Jaffe et al., 2001 and Swerdlow et al., 2008).

Molecular genetic analysis is also an important and rapidly developing area of histopathology with tissue used for diagnostic and prognostic purposes. It is beyond the scope of this chapter to list all the molecular investigations available, as these are covered in specific chapters.

It is not essential for an oncologist to have a detailed knowledge of histopathology, but a general understanding of pathological terms, tumour morphology, laboratory techniques and limitations is helpful. This chapter describes:

1. • specimen types,

2. • important microscopic descriptions of tumours,

3. • essential and practical immunohistochemical results and

4. • important aspects of working with pathologists

5. within busy MDTs.

Practical MDT information relating to pathology

Before obtaining a biopsy, the risks and benefits for the individual patient should be considered, especially when deciding which site is likely to most easily give a complete and accurate diagnosis, balancing the risk of failing to get a tissue diagnosis with the possible morbidity of the procedure. The patient will almost certainly be very anxious and any delays from repeated negative biopsies will not only make this worse but also delay treatment decisions. Sometimes a biopsy may not be necessary if treatment options are very limited.