Application of large format tissue processing in the histology laboratory

Abstract

In clinical, research and veterinary laboratories of North America, large format histology has more recently been improved with newer equipment and better methodology. Large tissue specimens are frequently sliced in the grossing room and processed in multiple smaller, standard size tissue cassettes. Justifiably, submitting more blocks inherently lends itself to a greater confidence in the accuracy of the diagnosis, yet guidelines for tissue sampling often suggest taking fewer samples. For example, large tumor specimen protocols recommend taking one standard sized tissue block for each cm diameter of tumor. However, cancers are the culmination of many complex changes in cell metabolism and often appear dissimilar at different tissue locations. As these changes have an uncertain behaviour, many other tissue samples are often taken from areas that appear to have either a variable texture or color. Consequently, at microscopy, the complete tissue sample may need to be reassembled like a jigsaw puzzle as the stained sections are frequently presented over many slides. This problem has easily been overcome by using large format cassettes since the entire cross-section of the tissue sample can often be viewed on a single slide. Because these cassettes can effectively hold up to ten times the volume of conventional standard size cassettes, they are a more efficient way of assessing large areas of tissue samples. This system is easily adapted for all tissue types and has become the established method for assessing large tissue samples in many laboratory settings.

Progress on deep learning in digital pathology of breast cancer: a narrative review

“…Large format histopathology is another efficient way for visualization of the tumor and resection margins as it eliminates the process of slicing the tissue into multiple blocks, avoiding undersampling of cancer specimens (123)(124)(125)(126). However, due to the limitations of the frozen technique, large sections are not available for intraoperative evaluation at present.…”

Updates in staging and pathologic evaluation of esophageal carcinoma following neoadjuvant therapy

“…50 This technique can also eliminate dissecting the tissue into numerous blocks and reduce the grossing time. 51 In patients receiving neoadjuvant therapy, LNs often become atrophic and difficult to recognize grossly, and sometimes only a few nodes can be identified despite an extensive search. There is no universally accepted guideline regarding the minimum number of LNs needed to report in EC resec-tions.…”

“…In cases where only patchy residual tumor cells are present and their distribution is not contiguous, the residual tumor is better assessed by using large (mega) blocks 50 . This technique can also eliminate dissecting the tissue into numerous blocks and reduce the grossing time 51 …”

Enhanced study of facial soft tissues using a novel large scale histology technique

“…Traditional methods for embedding and sectioning of larger specimens (e.g., in nitrocellulose) are hazardous, time‐consuming, and increasingly expensive (Gray, 1954; Mann, 1902). More recently described methods to study larger samples of soft tissues still fall short of the necessary size needed to study the complex soft tissue architecture of the face (Bryant et al, 2019).…”