What is the Significance of the In Transit or Interval Sentinel Node in Melanoma?

Excerpt

The advent of radionuclide lymphoscintigraphy as part of sentinel lymph node biopsy procedures for melanoma led to changes in our understanding of lymphatic anatomy, but the clinical significance of these changes are still undefined. Although it quickly became clear that primary melanomas frequently drained to lymph nodes outside of the traditional “major” basins (cervical, axillary, and ilioinguinal), it has been less clear what to do about these nodes—or even what to call them. Definitions of the three major nodal basins and their subdivisions are fairly standardized: the axillary basin consists of levels I–III; the ilioinguinal basin can be broken down into inguinofemoral, external, and common iliac and obturator nodes; and the cervical basin consists of levels I–VI. Whether to include occipital, pre- and postauricular, and parotid nodes as part of the cervical basin has not been totally standardized, but it seems reasonable to include them. For the extremities, epitrochlear and popliteal nodes are considered “minor” nodal basins, and internal mammary nodes often are but not always classified similarly (but probably should be). Beyond that, there is little standardization about what to call the many nodes that can be found in small numbers throughout the body, especially in the soft tissues of the posterior and lateral trunk, which occasionally serve as primary draining nodes for the skin. …