Histological study on pN upgrading of oral cancer

The International Union Against Cancer (UICC) does not define the number of sections required from each regional lymph node to record pTNM classificat ion. This study was designed to clarify the incidence of occult metastasis and to assess the pN upgrading of patients with oral cancer. Ultimately, th is study led to a proposal for appropriate semiserial sectioning guidelines . Five hundred fifty-four nonmetastatic cervical lymph nodes taken from 73 patients with oral cancer were subjected to hematoxylin-eosin (HE) staining and keratin immunohistochemistry. Micrometastases, defined as foci less th an or equal to 3 mm, were detected in 29 sites of 23 lymph nodes (4.2%) of 16 patients (21.9%). In 9 patients (12.3%) pN upgrading was needed: in 6 fr om pN0 to pN1, in 1 from pN0 to pN2b, and in 2 from pN1 to pN2b. The remain ing 13 lymph nodes with occult metastasis were found in 5 pN2b and 2 pN2c p atients, resulting in no pN upgrading. Occult metastasis was also detected in 6 small lymph nodes less than or equal to 5 mm in diameter. The average minor axis of the micrometastasis was 1.36+/-0.85 mm. We propose that the l ymph nodes should be cut and examined at l-mm intervals to detect micrometa static foci and to evaluate the pN classification accurately.