Introduction

Biopsies are frequently obtained during endoscopic investigation of esophageal and gastrointestinal (GIT) lesions and inflammatory conditions [1]. The histopathology laboratory will receive numerous small biopsies from multiple sites of each individual patient. Precise interpretation of endoscopic esophageal and gastrointestinal biopsies requires proper handling and processing of the specimens. In addition, a requirement for any valid histological interpretation is good communication between the endoscopist and the pathologist [2].

Specimen handling in the endoscopy unit

The appropriate handling of the specimen starts in the endoscopy unit, as the endoscopist should handle the tissue with care, gently removing it from the biopsy forceps [3]. In some institutions, the specimen is orientated before being placed flat on a supportive mesh, such as filter paper [3]. Whether the specimen is orientated or not, the biopsy should be fixed in 10% buffered formalin or equivalent fixative method. Buffered formalin achieves excellent tissue fixation, allowing for good‐quality staining with routine histological methods (e.g., hematoxylin and eosin, immunohistochemistry, Gram, Giemsa, etc.) as well as achieving good results in molecular tests (such as fluorescence in situ hybridization [FISH] or polymerase chain reaction [PCR]). The container should have the appropriate volume of fixative to minimize tissue desiccation and preserve tissue architecture [4].

It is of paramount importance to accurately label each specimen with the patient identification data and the site of the biopsy. The endoscopist should ensure that a separate container is used for biopsies taken from different sites so that the precise location of each biopsy can be properly identified [5]. In addition, a pathology request form containing any pertinent clinical information should be supplied with the samples [6].

In some cases, the suspected clinical diagnosis will require confirmation with electron microscopy. As the processing of these specimens is different from that of routine histology, in these circumstances a tissue sample should be fixed in glutaraldehyde and submitted to the pathology laboratory, highlighting the specific request for electron microscopy.

Specimen handling in the histopathology laboratory

Once the specimens are received in the histopathology laboratory, the case is registered and provided with a unique identification number.

Processing, embedding, and microtomy

Unfixed specimens cannot be directly infiltrated with paraffin. First, the water from the tissues must be removed by dehydration using increasing concentrations of alcohol.

The endoscopic biopsies may be processed and embedded either as individual samples or, more usually, combined into one multicassette. The use of a multicassette is not only cost‐effective but it also speeds up reporting time by the consultants (Figure 13.1).

All tissues should be orientated and embedded in a way that will facilitate optimal microtomy. GIT biopsies should be embedded on edge so that the mucosal surface is on one side (Figure 13.2).

If the endoscopy is described as “normal” on the accompanying request form, all blocks are trimmed to full face and a single slide of five serial 4 μ sections produced per block. If the endoscopy is described as “abnormal” a specific approach is taken. For example, if clinical details suggest celiac disease, 50 serial sections are cut from all biopsy samples taken from the duodenum. These sections are picked up across 10 slides. Slides 1, 5, and10 are stained and the rest stored as unstained spares. If there is any doubt, the biomedical scientist (histotechnician) should seek advice from the pathologist.

The mucosa must be sectioned perpendicular to its long axis [3]. As the specimen will naturally curl, some tangential section during microtomy can be expected. This may be especially relevant in samples from the small bowel, as the villi can artefactually appear short and broad, with a multilayered surface epithelium and an expanded lamina propria [3] (Figure 13.2b).

The adequate handling and processing of endoscopic biopsies for histological assessment depend on the necessary steps being taken by the endoscopist, pathologists, and biomedical scientists for reducing tissue trauma and processing artefacts. These artefacts may not produce any clinically significant harm, but they can create potential diagnostic problems for the pathologist during histopathological examination. Conversely, the resulting artefacts may indeed interfere with diagnosis and lead to an error with clinical consequences [7]. Artefacts related to biopsy trauma and specimen handling are listed in Table 13.1.

Biopsy trauma during sampling	Specimen handling in the laboratory
Tissue fragmentation	Pale staining due to poor fixation
Crushing artefact with condensation of lymphoplasmacytic cells	Tangential (oblique) orientation of the mucosa
Denudation of epithelium	Tissue curling during microtomy
Separation of surface epithelium from the underlying lamina propria	Multilayered surface and/or glandular epithelium
Hemorrhage in lamina propria	Air bubbles between the tissue and the coverslip
Edema of lamina propria	Contaminants (“floaters”) from another biopsy specimen
	Shrinkage during fixation
	Formalin pigment in the section