Step serial sectioning of lymph node in oral squamous cell carcinoma for micrometastasis and extra nodal extension: A cross-sectional study

Oral cavity carcinomas, categorized under head and neck cancers, are among the most common malignancies worldwide. India has one of the highest incidences worldwide and accounts for nearly 30% of annual global incidence. Occult metastasis (also known as micrometastasis) is defined as proliferation within the node of tumor tissue measuring > 0.2mm and <2mm in diameter and is often a potential pitfall for nodal metastasis. Extranodal extension (ENE)refers to growth of tumour outside the encapsulated lymph nodes that typically acts as natural barrier for tumor progression.
The aim of the study was to study step serial sectioning of lymph node in oral squamous cell carcinoma for detection of micrometastasis and extranodal extension
Objectives: The objective of the study was to classify oral squamous cell carcinomas based on pathological tumor(pT) and nodal stage(pN) and to determine the percentage increased nodal positivity in the node negative(pN0) cases of oral SCC on applying step serial sectioning and also calculate the percentage of increased ENE positive status in cases of ENE negative and nodal positive SCC with use of step serial sectioning.
Methodology: Study was cross sectional and was carried out at tertiary care centre ,Bareilly, UP for one year which included all histopathologically diagnosed node negative(N0) and pN stageN1-N3 with ENE negative status cases of oral SCC.  80 lymph nodes from diagnosed cases of oral squamous cell carcinoma were retrieved  and out of these 46 negative lymph nodes were examined to look for micrometastasis. 34 out of 80 lymph nodes were positive that were analysed for extranodal extension. All paraffin embedded tissue blocks of these cases were further trimmed at 100micrometer interval after the initial evalution, 2-3micron sections were obtained till the block was completely exhausted to look for micro metastasis and extra nodal extension.
Results: Out of 46 node negative cases, which yielded 704 sections , micrometastasis was detected in one node after step serial sectioning (2.2%) while 45 nodes (97.8%) were negative for micrometastasis. Nodal status was upstaged in one case(2.2%).However ENE status remained unchanged even after step serial sectioning.
Conclusion: Step serial sectioning can play an important role in diagnosing occult metastasis in node negative cases and spares the low risk patient from unnecessary treatment.