Immunostaining May Help Predict Nodal Metastasis Risk

Positive immunostaining with monoclonal antibody D2–40, together with younger patient age and lesion ulceration, might identify which melanoma patients are likely to have nodal metastasis and should undergo sentinel node biopsy, according to Dr. Firouzeh Niakosari of Sunnybrook Health Sciences Centre, Toronto, and associates.

"The recently developed monoclonal antibody [Mab] D2–40 reacts with endothelial cells of lymphatics but not with endothelial cells of blood vessels in normal tissues," the investigators wrote (Arch. Dermatol. 2008;144:462–7).

Mab D2–40 immunostaining more readily identifies lymphatic invasion in primary melanomas than does conventional staining with hematoxylin-eosin. Dr. Niakosari and associates assessed the technique's predictive value using blocks of primary tumor taken from 96 patients who were treated in 1998–2004 and had no clinical evidence of metastasis.

On biopsy, sentinel lymph nodes had been found to be positive in 23 of the cases.

Mab D2–40 immunostaining was positive for invasion of the lymphatic vessels within the tumor samples in 32 of the 96 cases (33%). The result was correct in ruling out lymphatic invasion in 56 (77%) of the cases that proved to have no invasion on sentinel node biopsy, and it was correct in identifying lymphatic invasion in 15 (65%) of the cases that did have lymphatic invasion on sentinel node biopsy.

On its own, then, the technique had a negative predictive value of 88% and a positive predictive value of 47%, the investigators found.

Mab D2–40 immunostaining was even more predictive when the results were combined with two clinical factors: younger patient age and the presence of ulceration in the lesion. "The probability of sentinel lymph node positivity was 13% when lymphatic invasion identified by immunostaining with Mab D2–40 was negative, no ulceration was present, and the patient was 50 years or older," they noted.

In cases in which the immunostaining indicated that there was lymphatic invasion, ulceration was present, and the patient was younger than 50 years, the probability of sentinel lymph node positivity increased to 61%, Dr. Niakosari and associates reported.

Lymphatic invasion on Mab D2–40 immunostaining correlated with deeper Clark Level of Invasion and increased Breslow tumor thickness, "indicating that lymphatic invasion occurs more frequently in later stages of melanoma," they wrote.