Introduction
Lymphatic mapping for identification and subsequent removal of the sentinel lymph
node (SLN) is an established procedure in breast cancer and cutaneous melanoma to
minimize the extent of surgery (and thus, associated morbidity), simplify histopathological
processing and subsequently provide prognostic information and help choose the optimal
patient management. Established methods for SLN mapping include visual identification
of nodal staining after peritumoral injection of a (blue) dye or the use of lymphoscintigraphy
with technetium-labelled nanocolloid. In experienced hands, success rates for both
methods exceed 95 %, nonetheless in some patients they fail despite correct application
and imaging techniques. Potential reasons for false-negative SLN detection rates –beyond
poor tracer injection technique or imaging of the wrong nodal basin- include inadequate
pathologic examination of the SLN or complete replacement of the SLN with neoplastic
disease, causing the injected tracer to completely bypass the infiltrated node [1].
Beyond colloid particles, the more specific receptor-targeting small molecule [99mTc]Tilmanocept has recently been approved for scintigraphic SLN detection. Tilmanocept,
or mannosyl diethylene-triamine-pentaacetate (DTPA) dextran, has a small molecular
size of approximately 7 nm and works via specific binding to the mannose receptor
(CD206) [2]. The mannose receptor is particularly overexpressed on macrophages and dendritic
precursor cells within lymph nodes, thus uptake in lymph nodes is not dependent on
particle size [2], [3]. In pilot studies scintigraphic SLN detection with [99mTc]Tilmanocept was superior to dye staining [4]. Given its beneficial properties, [99mTc]Tilmanocept might offer advantages over the alternatively used radiocolloids. We
present four cases of [99mTc]Tilmanocept application after inconclusive or unsuccessful attempts of SLN detection
using [99mTc]nanocolloid lymphoscintigraphy.
