Page 26 - Textbook of Pathology, 6th Edition

10 SURGICAL PATHOLOGY PROTOCOL
REQUEST FORMS. The first and foremost task of the
clinician requesting tissue diagnosis is to send a completed
request form containing patient’s identification data (ID)
matching with that on accompanying specimen container. The
body of the request form must contain the entire relevant infor-
mation about the case and the disease (history, physical and
operative findings, results of other relevant biochemical/
haematological/radiological investigations, and clinical and
SECTION I
differential diagnosis) and reference to any preceding cytology
or biopsy examination done in the pathology services.
TISSUE ACCESSION. The laboratory staff receiving the
biopsy specimen must always match the ID of the patient
on the request form with that on the specimen container.
For routine tissue processing by paraffin-embedding
technique, the tissue must be put in either appropriate
fixative solution (most commonly 10% formol-saline or 10%
buffered formalin) or received fresh-unfixed. For frozen
section, the tissue is always transported fresh-unfixed. Figure 2.1 Automatic tissue processor for processing by paraffin-
Microwave fixation may also be used in the laboratory for embedding technique.
rapid fixation and processing of routine surgical specimens. (Thermo Shandon, UK). Courtesy: Towa Optics (India) Pvt. Ltd., New
Delhi.
GROSS ROOM. Gross examination of the specimen received In order to avoid contamination of the laboratory with
in the laboratory is the next most important step. Proper gross vapours of formalin and alcohols, vacuum tissue processors
tissue cutting, gross description and selection of representative having closed system are also available.
tissue sample in larger specimens is a crucial part of the Embedding of tissue is done in molten wax, blocks of
pathologic examination of tissue submitted. Complacency at which are prepared using metallic L (Leuckhart’s) moulds.
this step cannot be remedied at a later stage and might Nowadays, plastic moulds in different colours for blocking
require taking the tissue pieces afresh if the specimen is large different biopsies are also available. The entire process of
General Pathology and Basic Techniques
enough and that may delay the report, or if the biopsy is small embedding of tissues and blocking can be temperature-
and lost in processing the entire surgical procedure for controlled for which tissue embedding centres are available
biopsy may have to be done again. Modern compact grossing (Fig. 2.2). The blocks are then trimmed followed by sectioning
stations have inbuilt system for recording gross description by microtomy, most often by rotary microtome, employing
through dictaphone without the aid of an assistant to write either fixed knife or disposable blades (Fig. 2.3).
it. Some laboratories have a protocol of doing gross specimen Cryostat or frozen section eliminates all the steps of tissue
photography and specimen radiography, before and after processing and paraffin-embedding. Instead, the tissue is
tissue cutting for documentation. quickly frozen to ice at about –25°C which acts as embed-
Calcified tissues and bone are subjected to decalcification ding medium and then sectioned (Fig. 2.4). Sections are then
to remove the mineral and soften the tissue by treatment with ready for staining. Frozen section is a rapid intraoperative
decalcifying agents such as acids and chelating agents (most diagnostic procedure for tissues before proceeding to a major
often aqueous nitric acid).
It is mandatory that all the gross-room personnel follow
strict precautions in handling the tissues infected with
tuberculosis, hepatitis, HIV and other viruses.

HISTOPATHOLOGY LABORATORY. Tissue cassettes
along with unique number given in the gross room to the
tissue sample is carried throughout laboratory procedures.
Majority of histopathology departments use automated tissue
processors (Fig. 2.1) having 12 separate stages completing the
cycle in about 18 hours by overnight schedule as under:
10% formalin for fixation;
ascending grades of alcohol (70%, 95% through 100%) for
dehydration for about 5 hours in 6-7 jars,
xylene/toluene/chloroform for clearing for 3 hours in two
jars; and Figure 2.2 Tissue embedding centre for paraffin technique
paraffin impregnation for 6 hours in two thermostat-fitted (Histocentre).
(Thermo Shandon, UK). Courtesy: Towa Optics (India) Pvt. Ltd., New
waxbaths. Delhi.