WILLIAMSBURG, VA. Sentinel lymph node biopsy should be reserved only for squamous cell carcinoma patients whose primary tumors have a high-risk profile, according to Dr. Merrick Ross.
"Clearly, the routine use of sentinel node biopsy is not indicated in these patients, but its selective use in high-risk squamous cell carcinoma [SCC] seems rational," said Dr. Ross at a meeting of the American Society for Mohs Surgery. "This is why it's important for us to continue to define exactly what constitutes a high-risk squamous cell tumor."
High-risk features of SCC include anatomical location, thickness, size, perineural invasion, and the immunocompetence of the patient.
Increasing size is associated with decreased local control and the increased presence of positive lymph nodes. A size of 2 cm "seems to be the most relevant break point," said Dr. Ross, professor of surgical oncology at the University of Texas M.D. Anderson Cancer Center, Houston. "Studies have shown that up to 50% of SCCs larger than that will have nodal involvement. However, to date there is no multivariate analysis that demonstrates size as an independent predictor of nodal disease."
Most studies identify 4-5 cm as the high-risk break point for tumor thickness, he said. In a large German study of 550 patients, only 3% of those with tumors less than 5 mm thick had nodal metastasis, compared with more than 17% of those with thicker tumors, Dr. Ross noted (Cancer 1997;79:915-9).
High-grade tumors are more likely than low-grade tumors to have nodal disease, said Dr. Ross, with 17% of high-grade tumors showing metastasis, compared with 4% of lower-grade tumors. When the German investigators looked at grade distribution according to nodal involvement, 44% of node-positive patients had high-grade primary tumors, whereas only 5% of node-negative patients had high-grade tumors.
Local recurrence is strongly associated with nodal involvement, just as it is with larger size, thicker tumors, narrow excision margins, and anatomical site. Up to 45% of recurrent presentations will have nodal disease, Dr. Ross said.
Lesions that arise on the lip, around the ear, and in the anogenital region are particularly risky. A 2006 study found that 27% of SCCs on the external ear had nodal disease, as did more than 20% of T3- and T4-stage lip lesions (Aust. J Derm. 2006;47:28-33).
The overall health of the patient is another important risk factor. "Patients with HIV [disease] or other immunodeficiency diseases are at an increased risk for metastasis, as are those with any chronic hematologic malignancy" Dr. Ross said.