Pathologic evaluation of sentinel lymph nodes in oral squamous cell carcinoma.

Abstract

The objective of this study was to determine the relative efficacy of different methods of pathologic evaluation of sentinel lymph nodes. In this prospective study, sentinel nodes were evaluated for occult metastasis using frozen section, imprint-cytology, hematoxylin-eosin staining, serial step sectioning (SSS) with hematoxylin-eosin, and immunohistochemistry (IHC). Metastases were classified into macrometastasis (>2.0 mm), micrometastasis (0.2 mm-2.0 mm), isolated tumor cells (<0.2 mm). Occult metastasis was detected in 20 of 80 patients. Frozen section and imprint cytology identified metastasis in 10 of 20 patients, hematoxylin-eosin stain in 13 patients; SSS upstaged the disease in a further 7 patients (9%). Frozen section detected macrometastasis in 7 of 8 cases but failed to detect smaller metastases (missed micrometastasis in 4 of 7 and isolated tumor cells in 5 of 5). SSS upstaged the disease by 10%, and sensitivity and negative predictive value of SSS with hematoxylin-eosin stain were 90% and 97%, respectively. Frozen section and imprint cytology are not effective in identifying occult metastasis. IHC and SSS are required to identify micrometastasis and isolated tumor cells.