Rates of flow of technetium 99m--labeled human serum albumin from peripheral injection sites to sentinel lymph nodes

A Physiologically Based Pharmacokinetic Framework for Quantifying Antibody Distribution Gradients from Tumors to Tumor-Draining Lymph Nodes

Immune checkpoint blockades prescribed in the neoadjuvant setting are now under active investigation for many types of tumors, and many have shown early success. The primary tumor (PT) and tumor-draining lymph node (TDLN) immune factors, along with adequate therapeutic antibody distributions to the PT and TDLN, are critical for optimal immune activation and anti-tumor efficacy in neoadjuvant immunotherapy. However, it remains largely unknown how much of the antibody can be distributed into the PT-TDLN axis at different clinical scenarios. The goal of the current work is to build a physiologically based pharmacokinetic (PBPK) model framework capable of characterizing antibody distribution gradients in the PT-TDLN axis across various clinical and pathophysiological scenarios. The model was calibrated using clinical data from immuno-PET antibody-imaging studies quantifying antibody pharmacokinetics (PK) in the blood, PTs, and TDLNs. The effects of metastatic lesion location, tumor-induced compression, and inflammation, as well as surgery, on antibody concentration gradients in the PT-TDLN axis were characterized. The PBPK model serves as a valuable tool to predict antibody exposures in various types of tumors, metastases, and the associated lymph node, supporting effective immunotherapy.

Histologic Patterns of Cutaneous Metastases of Breast Carcinoma: A Clinicopathologic Study of 232 Cases

ABSTRACT

Cutaneous metastasis may be the initial sign of internal malignancy but more often represents a late manifestation of widely disseminated disease. Breast carcinoma is the most common malignancy to metastasize to the skin. Although several studies have detailed the histopathologic patterns of cutaneous metastasis from internal malignancies, very little has been published regarding metastases of breast carcinoma to the skin. Furthermore, the histopathologic and clinical features observed in the cases of breast carcinoma with local skin involvement as opposed to cases exhibiting distant cutaneous metastases have not been adequately investigated. We have reviewed 232 cases of breast carcinoma with cutaneous metastases from 2 large institutions. All cases of carcinoma of the breast with involvement of the skin of the anterior chest wall were compared with those with distant cutaneous metastases. Two hundred thirty-two cases in 199 patients were included, of which 126 had skin involvement exclusively involving the ipsilateral anterior chest, and 106 had biopsy-proven distant cutaneous metastases. Twelve patients had both local and distal spread. Distant cutaneous metastases showed a predilection for the contralateral anterior chest wall area, followed by the head and neck, back, and abdomen. Histologically, most of the tumors presented in this series showed features of infiltrating ductal carcinoma. In both ipsilateral and distant metastases, the tumors demonstrated little change in histologic features from the primary lesion; however, the distant metastases showed a tendency to display more poorly differentiated features. The mean patient survival when cutaneous involvement was localized to the skin of the anterior chest wall was 23 months as compared with 20.6 months when distant sites were affected. A comparison of the clinicopathologic features of the patients presented in this series suggests that alternate biological mechanisms may apply for local and distant skin metastases from breast carcinoma.

Programmable multistage drug delivery to lymph nodes

Therapeutic delivery selectively to lymph nodes has the potential to address a variety of unmet clinical needs. However, owing to the unique structure of the lymphatics and the size-restrictive nature of the lymph node reticular network, delivering cargo to specific cells in the lymph node cortex and paracortex is difficult. Here, we describe a delivery system to overcome lymphatic and intra-lymph node transport barriers by combining nanoparticles that are rapidly conveyed to draining lymph nodes after administration in peripheral tissues with programmable degradable linkers. This platform enables the controlled release of intra-lymph-mobile small-molecular cargo, which can reach vastly more immune cells throughout the lymph node than either the particles or free compounds alone. The release rate can be programmed, allowing access to different lymph node structures and therefore specific lymphocyte subpopulations. We are thus able to alter the subtypes of drugged lymph node cells to improve immunotherapeutic effects.

Sentinel Node Identification in Melanoma: Current Clinical Impact, New Emerging SPECT Radiotracers and Technological Advancements. An Update of the Last Decade

BACKGROUND

Melanoma is the most lethal skin cancer with a mortality rate of 262 cases per 100.000 cases. The sentinel lymph node (SLN) is the first lymph node draining the tumor. SLN biopsy is a widely accepted procedure in the clinical setting since it provides important prognostic information, which helps patient management, and avoids the side effects of complete lymph node dissection. The rationale of identifying and removing the SLN relies on the low probability of subsequent metastatic nodes in case of a negative histological exam performed in the SLN.

DISCUSSION

Recently, new analytical approaches, based on the evaluation of scintigraphic images are also exploring the possibility to predict the metastatic involvement of the SLN. 99mTc-labeled colloids are still the most commonly used radiotracers but new promising radiotracers, such as 99mTc- Tilmanocept, are now on the market. In the last decades, single photon emission computed tomography- computerized tomography (SPECT/CT) has gained wider diffusion in clinical departments and there is large evidence about its superior diagnostic accuracy over planar lymphoscintigraphy (PL) in the detection of SLN in patients with melanoma. Scientists are also investigating new hybrid techniques combining functional and anatomical images for the depiction of SLN but further evidence about their value is needed.

CONCLUSION

This review examined the predictive and prognostic factors of lymphoscintigraphy for metastatic involvement of SLN, the currently available and emerging radiotracers and the evidence of the additional value of SPECT/CT over PL for the identification of SLN in patients with melanoma. Finally, the review discussed the most recent technical advances in the field.

Proteolysis and Oxidation of Therapeutic Proteins After Intradermal or Subcutaneous Administration

The intradermal (ID) and subcutaneous (SC) routes are commonly used for therapeutic proteins (TPs) and vaccines; however, the bioavailability of TPs is typically less than small molecule drugs given via the same routes. Proteolytic enzymes in the dermal, SC, and lymphatic tissues may be responsible for the loss of TPs. In addition, the TPs may be exposed to reactive oxygen species generated in the SC tissue and the lymphatic system in response to injection-related trauma and impurities within the formulation. The reactive oxygen species can oxidize TPs to alter their efficacy and immunogenicity potential. Mechanistic understandings of the dominant proteolysis and oxidative routes are useful in the drug discovery process, formulation development, and to assess the potential for immunogenicity and altered pharmacokinetics (PK). Furthermore, in vitro tools representing the ID or SC and lymphatic system can be used to evaluate the extent of proteolysis of the TPs after the injection and before systemic entry. The in vitro clearance data may be included in physiologically based pharmacokinetic models for improved PK predictions. In this review, we have summarized various physiological factors responsible for proteolysis and oxidation of TPs after ID and SC administration.

Understanding the Monoclonal Antibody Disposition after Subcutaneous Administration using a Minimal Physiologically based Pharmacokinetic Model

PURPOSE

Monoclonal antibodies (mAbs) are commonly administered by subcutaneous (SC) route. However, bioavailability is often reduced after SC administration. In addition, the sequential transfer of mAbs through the SC tissue and lymphatic system is not completely understood. Therefore, major objectives of this study were a) To understand absorption of mAbs via the lymphatic system after SC administration using physiologically based pharmacokinetic (PBPK) modeling, and b) to demonstrate application of the model for prediction of SC pharmacokinetics (PK) of mAbs.

METHODS

A minimal PBPK model was constructed using various physiological parameters related to the SC injection site and lymphatic system. The remainder of the body organs were represented using a 2-compartment model (central and peripheral compartments), with parameters derived from available intravenous (IV) PK data. The IV and SC clinical PK data of a total of 10 mAbs were obtained from literature. The SC PK data were used to estimate the lymphatic trunk-lymph node (LN) clearance.

RESULTS

The mean estimated lymphatic trunk-LN clearance obtained from 37 SC PK profiles of mAbs was 0.00213 L/h (0.001332 to 0.002928, 95% confidence intervals). The estimated lymphatic trunk-LN clearance was greater for the mAbs with higher isoelectric point (pI). In addition, the estimated clearance increased with decrease in the bioavailability.

CONCLUSION

The minimal PBPK model identified SC injection site lymph flow, afferent and efferent lymph flows, and volumes associated with the SC injection site, lymphatic capillaries and lymphatic trunk-LN as important physiological parameters governing the absorption of mAbs after SC administration. The model may be used to predict PK of mAbs using the relationship of lymphatic trunk-LN clearance and the pI. In addition, the model can be used as a bottom platform to incorporate SC and lymphatic in vitro clearance data for mAb PK prediction in the future.

Lymphatic transit rate as a novel predictive parameter for nodal metastasis in primary truncal skin cancers

Prediction of nodal metastasis in skin cancer before sentinel lymph node (SLN) biopsies is ideal to avoid unnecessary SLN biopsy performance. Primary truncal skin cancers are characterized by the lymphatic flow that drains from the primary lesion, occasionally to plural nodal basins. The scintigraphic appearance time (SAT), defined as the time between radionuclide injection and first SLN visualization, can potentially predict nodal metastasis, and a short SAT is a predictive parameter for metastasis. We recently introduced a novel method to measure the lymphatic flow rate using dynamic lymphoscintigraphy exhibiting a time-activity curve in the SLN. The time at which the count reaches a plateau in the SLN is termed the scintigraphic saturation time (SST) and can be a good alternative to the SAT. Moreover, the value obtained by division of the distance between the primary lesion and the SLN by the SST was termed the lymphatic transit rate (LTR), which represents the scintigraphic saturation velocity. In the present study, we evaluated LTR as a predictive parameter for nodal metastasis. Data for 22 lymph nodes from 18 patients with primary truncal skin cancers were used. Histopathologically, nodal metastasis was determined in nine nodes of eight patients. Because the mean LTR were 1.84 cm/min in non-metastatic SLN and 2.38 cm/min in metastatic SLN, the LTR was significantly higher in metastatic SLN than in non-metastatic SLN. All SLN with LTR of less than 1.8 cm/min were histopathologically evaluated as non-metastatic. The LTR may be a predictive indicator for nodal metastasis.

Measurement of cutaneous lymphatic flow rates in patients with skin cancer: area extraction method

Some recent reports have revealed that the long scintigraphic appearance time (SAT), defined as the time between radionuclide injection and first sentinel lymph node (SLN) visualization in lymphoscintigraphy, is a negative predictive parameter of nodal metastasis in patients with melanoma. However, most of the methods used to measure the SAT were ambiguous because they utilized visualization in lymphoscintigraphy. We herein introduce a novel method by which to measure the SAT and lymphatic flow rate. The data of 33 patients with primary skin cancer were used. Sequential images were obtained using dynamic lymphoscintigraphy, and a time-activity curve of the SLN was created. The time at which the counts reached plateau was newly defined as an alternative to the SAT and was termed the scintigraphic saturation time (SST). The figure obtained by division of the distance by the SST was newly defined as an alternative to the lymphatic flow rate and termed the lymphatic transit rate (LTR). The SST was clearly determined. It ranged from 220 to 1430 s (mean, 805 s). Pathological examination revealed nodal metastasis in five patients. In 28 patients without metastasis, the mean LTR was in the order of lower limbs (4.07 ± 0.35 cm/min), upper limbs (2.67 ± 0.33 cm/min), trunk (1.79 ± 0.47 cm/min), and head and neck (1.11 ± 0.22 cm/min). The LTRs were higher in patients with nodal metastasis than those without. This method may be effective for accurate measurement of the SAT and lymphatic flow rate.

Minimally invasive quantification of lymph flow in mice and rats by imaging depot clearance of near-infrared albumin

There is a lack of available methods to noninvasively quantify lymphatic function in small experimental animals, a necessity for studies on lymphatic system pathophysiology. We present a new method to quantify lymph flow in mice and rats, based on optically monitoring the depot clearance of near-infrared fluorescently labeled albumin and subsequent calculation of removal rate constants (k). BSA was conjugated with Alexa680 NHS ester and remained stable in protein-rich solutions without free dye dissociation. To assess lymph flow, mice or rats were imaged every 30 or 60 min during a 3- to 6-h period following an intradermal injection of 0.5 or 1 μl Alexa680-albumin. Mice were awake between measurements, whereas rats were anesthetized throughout the experiment. The k, a parameter defined as equivalent to lymph flow, was calculated from the slopes of the resultant log-linear washout curves and averaged -0.40 ± 0.03 and -0.30 ± 0.02%/min for control C57BL/6 and C3H mice, respectively. Local administration of the vasoconstrictor endothelin-1 in mice led to a significant reduction in k, whereas overhydration in rats increased k, reflecting the coupling between capillary filtration and lymph flow. Furthermore, k was 50% of wild type in lymphedema Chy mice where dermal lymphatics are absent. We conclude that lymph flow can be determined as its rate constant k by optical imaging of depot clearance of submicroliter amounts of Alexa680-albumin. The method offers a minimally invasive, reproducible, and simple alternative to assess lymphatic function in mice and rats.

Slow dynamic lymphoscintigraphy is not a reliable predictor of sentinel-node negativity in cutaneous melanoma

We reviewed data from 160 consecutive patients (89 M/71 F; 53.5 [range, 9-88] years) who had under-gone lymphoscintigraphy and sentinel lymph node biopsy (SNB) in our hospital for histologically proven cutaneous malignant melanoma (CMM) (located on the upper limb: 33; lower limb: 57; trunk: 44; and head and neck: 26 patients), with a Breslow index > 1 mm and without clinical or radiologic evidence of metastatic spread. Colloidal (99m)Tc-rhenium sulfide (36-76 MBq) was injected intradermally in the four quadrants around the tumorectomy scar, followed by dynamic acquisition and static imaging. SN(s) were identified in 157 patients (overall identification rate, 98%). Fast (< 20 minutes), intermediate (20-30 minutes), or slow (> 30 minutes) lymphatic drainage was observed, respectively, in 122 (78%), 24 (15%), or 11 (7%) cases. Overall malignancy rate was 15%, respectively found in 19 (16%), 2 (8%), and 2 (18 %) patients with fast, intermediate, or slow drainage. No statistical difference between SN-positivity rates of patients with fast (19/122 = 16%) versus intermediate or slow drainage (4/35 = 11.4%) was observed (p = 0.69). Therefore, lymphoscintigraphic SN appearance time in CMM patients is unable both to predict SN metastasis and spare them from undergoing SN excision.

Noninvasive quantitative imaging of lymph function in mice

BACKGROUND

Whereas functional lymph imaging in rodents is imperative for drug discovery of lymph therapeutics, noninvasive imaging of propulsive lymph function in rodents has not been reported previously. Herein, we present a noninvasive and rapid approach to measure lymphatic function in a rodent model using a near-infrared (NIR) dye to minimize background autofluorescence and maximize tissue penetration.

METHODS AND RESULTS

Mice were dynamically imaged following intradermal (i.d.) injection of 2 to 10 microL of 1.3 mM of indocyanine green (IC-Green) into the tail and the limb. Our results demonstrate the ability to image the IC-Green trafficking from the lymph plexus, through lymph vessels and lymphangions, to the ischial nodes in the tail, and to the axillary nodes in the limb. Our results show that lymph flow velocity from the propelled IC-Green "packet" in the lymph vessels in the tail ranged from 1.3 to 3.9 mm/s and the fluorescence intensity peaks repeated on an average of every 51.3 +/- 17.4 seconds in five animals. While pulsatile lymph flow was detected in the deep lymph vessels, lymph propulsion was not visualized in the superficial lymphatic network in the tail. In axillary lymphatic imaging, propulsive lymph flow was also detected. The intensity profile shows that the lymph flow velocity ranged from 0.28 to 1.35 mm/s at a frequency ranging from 0.72 to 11.1 pulses per minute in five animals.

CONCLUSIONS

Our study demonstrates the ability to noninvasively and quantitatively image propulsive lymph flow, which could provide a new method to investigate lymph function and its change in response to potential therapeutics.

Imaging steps of lymphatic metastasis reveals that vascular endothelial growth factor-C increases metastasis by increasing delivery of cancer cells to lymph nodes: therapeutic implications

Preclinical and clinical studies positively correlate the expression of vascular endothelial growth factor (VEGF)-C in tumors and the incidence of lymph node metastases. However, how VEGF-C regulates individual steps in the transport of tumor cells from the primary tumor to the draining lymph nodes is poorly understood. Here, we image and quantify these steps in tumors growing in the tip of the mouse ear using intravital microscopy of the draining lymphatic vessels and lymph node, which receives spontaneously shed tumor cells. We show that VEGF-C overexpression in cancer cells induces hyperplasia in peritumor lymphatic vessels and increases the volumetric flow rate in lymphatics at the base of the ear by 40%. The increases in lymph flow rate and peritumor lymphatic surface area enhance the rate of tumor cell delivery to lymph nodes, leading to a 200-fold increase in cancer cell accumulation in the lymph node and a 4-fold increase in lymph node metastasis. In our model, VEGF-C overexpression does not confer any survival or growth advantage on cancer cells. We also show that an anti-VEGF receptor (VEGFR)-3 antibody reduces both lymphatic hyperplasia and the delivery of tumor cells to the draining lymph node, leading to a reduction in lymph node metastasis. However, this treatment is unable to prevent the growth of tumor cells already seeded in lymph nodes. Collectively, our results indicate that VEGF-C facilitates lymphatic metastasis by increasing the delivery of cancer cells to lymph nodes and therapies directed against VEGF-C/VEGFR-3 signaling target the initial steps of lymphatic metastasis.

Preclinical models of regional lymph node tumor metastasis

Animal models have produced vital information regarding the mechanisms of RLN metastasis. Modern imaging and molecular techniques have made it clear that growing tumors secrete cytokines that induce invasion, angiogenesis, lymphangiogenesis, increased intratumoral IFV and IFP, increased fluid flow from the tumor to the surrounding tissues, increased lymphatic flow, an increase in the rate of entry of tumor cells into lymphatic capillaries, and an increased number of tumor cells reaching the RLN(s). This is important knowledge that will help direct translational research in human patients. We can look forward to continued improvement in the management of human tumors that metastasize to the RLNs.

Insights into the mechanisms of lymph node metastasis

The mechanisms by which malignant tumors leave the primary tumor site, invade lymphatics, and metastasize to regional lymph nodes (RLNs) are complex and interrelated. Although the phenomenon of lymph node metastasis has been recognized for over 200 years, the exact mechanisms have only recently been the subject of intense interest and sophisticated experimentation. Sentinel lymph node biopsy has rapidly entered the clinical mainstream for melanoma and breast carcinoma, and this technique has provided confirmation of the orderly anatomic progression of tumor cells from primary site to the RLNs through lymphatic capillaries and trunks. Exciting studies involving the pathophysiology of interstitial fluid pressure in tumors and the peritumoral extracellular matrix have focused on lymphatic flow and tumor microenvironment and microcirculation. Molecular techniques have led to the definition of unique markers found on lymphatic endothelial cells. These markers have enabled scientists to identify peritumoral and intratumoral lymphatics and to visualize the ingrowth of tumor cells into the lumena of lymphatic capillaries. Tumor-secreted cytokines, such as vascular endothelial growth factors (VEGF)-C and -D, bind to VEGF receptors on lymphatic endothelial cells and induce proliferation and growth of new lymphatic capillaries; this process is similar to the well-known mechanism of angiogenesis, which results from the proliferation of new blood vessel capillaries. Lymphangiogenesis is associated with an increased incidence of RLN metastasis, and it is possible that this step is essential to the metastatic process. Directional movement toward lymphatics and lymph nodes appears to follow a chemokine gradient, and it is likely that some tumor cells that express certain types of chemokine receptors are more likely to metastasize to the RLNs. In contrast, tumor cells that do not express specific receptors that are responsive to lymphatic chemokines may not metastasize. New knowledge regarding the molecules involved in these processes should enable improvements in prognostic and possibly therapeutic approaches to the management of malignant tumors.

Successful treatment of 19 consecutive groin lymphoceles with the assistance of intraoperative lymphatic mapping

Postoperative groin lymphoceles that fail to resolve spontaneously or with interventional therapy present a formidable problem that is associated with a high degree of morbidity. Numerous interventional methods and operative techniques have been described to treat these fluid collections, yet recurrence rates remain high. The use of lymphatic mapping has gained widespread use in the treatment of cutaneous malignancies and breast cancer and has been proven effective in delineating the course of lymphatic channels. We present here a series of 17 consecutive patients with 19 problematic groin lymphoceles who were treated with the assistance of intraoperative lymphatic mapping using isosulfan blue dye. To date there have been no recurrences and minimal morbidity associated with the technique and prescribed postoperative treatment regimen.

Intraoperative lymphatic mapping to treat groin lymphorrhea complicating an elective medial thigh lift

Groin lymphoceles and lymphorrhea are a rare complication of medial thigh lift procedures. The author describes a case in which a very thin patient developed groin lymphorrhea after an uncomplicated medial thigh lift procedure. Initial treatment interventions, including edema control and the placement of a drain with surgical exploration, failed to control the lymphatic leak. Additionally, the onset of an infection and abscess formation complicated the treatment efforts. Using techniques well established in treating cutaneous malignancies, the lymphocele was treated successfully by identifying three separately damaged lymphatic channels with the use of intraoperative lymphatic mapping with blue dye. No drains were needed and the immediate cessation of lymph flow was noted. Using this novel adaptation of a well-known technique, the groin lymphocele was able to be repaired quickly and effectively with minimal morbidity and no evidence of recurrence to date.

Current therapy of cutaneous melanoma

Melanoma is a growing public health problem. Optimal care of the melanoma patient is multidisciplinary, but plastic surgeons and other surgical specialties play a central role in the management of these patients. Although surgery remains the mainstay of therapy for melanoma, several recent clinical studies have helped to clarify the biology of the disease and have changed the patterns of care for patients with melanoma. The advent of lymphatic mapping for interrogation of regional lymph nodes and interferon as the first effective postsurgical adjuvant therapy have had a major impact on the care of melanoma in the United States and elsewhere. This article will review the current clinical approach and therapy for cutaneous melanoma. The diagnosis, prognostic variables, staging evaluation, current surgical and medical treatment, and follow-up guidelines for patients with all stages of melanoma are reviewed. Recent studies, controversies, and directions of future investigational therapies will be discussed.

[Identification of axillary sentinel node by lymphotropic dye in breast cancer. Feasibility study apropos of 128 cases]

AIM OF THE STUDY

The goal of this study was to evaluate the technical feasibility of sentinel node biopsy in breast cancer and its predictivity of axillary node status.

PATIENTS AND METHODS

Between January 1996 and June 1997, 128 patients with invasive breast carcinomas, referred to the Cancer Center of Strasbourg and Lyon (France), underwent lymphatic mapping (Patent Blue dye) and sentinel node biopsy followed by axillary clearance (Berg's level I to II).

RESULTS

Sentinel node was identified in 76.5% of cases and was predictive of axillary status in 94.9% of cases. The false negative rate of the procedure was 5.1%. Sentinel lymph node was involved in 43.9% of cases and it was the only one involved in 30.2% of cases. The sensitivity of the procedure was 94% (CI: 95% = [88%-98%]) and its specificity 100%.

CONCLUSION

Actually considered as new attractive procedure under ongoing evaluation in prospective controlled trials, this study confirms the feasibility and reproductibility of lymphatic mapping and sentinel node biopsy, first stage before entering a new era of minimally invasive axillary surgery in breast cancer.

The Role of Selective Lymphadenectomy in Breast Cancer

BACKGROUND: Axillary node dissection is considered a standard staging procedure in patients with breast cancer. The procedure is associated with significant morbidity and provides pathologists with many lymph nodes to evaluate. METHODS: A total of 174 women participated in a trial that included preoperative lymphoscintigraphy and intraoperative lymphatic mapping using a combination of a vital blue dye and radiocolloid mapping. RESULTS: The intraoperative lymphatic mapping correctly identified a sentinel lymph node (SLN) in 160 (92%) of 174 patients. One skip metastasis (0.7%) occurred in 136 women who had a subsequent complete node dissection. CONCLUSIONS: Lymphatic mapping and SLN biopsy using a combination of mapping techniques provide accurate nodal staging for women with breast cancer. With this technique, approximately 70% to 80% of women with no axillary metastases could be spared the morbidity of a complete node dissection.

Lymphoscintigraphy, the sentinel node concept, and the intraoperative gamma probe in melanoma, breast cancer, and other potential cancers

There is a resurgence of interest in lymphoscintigraphy because of attention to the sentinel node concept and the availability of the surgical gamma probe that can be used in the operating room to localize radiolabeled sentinel nodes. Conventional surgical management of melanoma has been altered for intermediate thickness tumors such that lymph node dissection is performed for a lymph node bed only if the sentinel node is tumor positive on histological exam after gamma probe-guided excision. This approach is cost effective, saving about 80% of these patients (sentinel node tumor negative) the cost and morbidity of unnecessary "elective lymph node dissection." In addition, a biopsy can be performed on all lymph node beds that receive lymphatic drainage from the tumor site thereby improving staging and perhaps survival by providing the most appropriate therapy. Substantial work has been done to develop optimum imaging techniques and the best radiopharmaceutical preparation to achieve accurate, reproducible lymphatic drainage images. Our methodology includes the following intradermal injections of a technetium 99m sulfur colloid (modified preparation) are followed by dynamic imaging (10 seconds per frame); static imaging up to 30 minutes and late imaging at 1 to 2 hours. Images show lymphatic channels that lead to sentinel nodes in 1, 2, 3, or more anatomic locations. Surgical management is altered to include sampling sentinel nodes of nodal beds, many of which would not have been sampled by previous conventional surgical estimates of lymphatic drainage. While clinical success of lymphoscintigraphy and intraoperative probe localization of the sentinel node in melanoma is evident, use of lymphoscintigraphy and the sentinel node concept in breast cancer is investigative, but promising. The radiopharmaceutical is injected around the tumor in the breast followed by imaging to delineate lymphatic drainage to the sentinel node(s). Optimum methodologies for radiopharmaceutical, volume and/or activity of injectate, and imaging have yet to be determined. Breast lymphatic drainage can be to axilla, internal mammary, and/or supraclavicular nodes in any combination.