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

Dissecting the Lymphatic System to Predict Melanoma Metastasis

Melanoma is the most lethal form of skin cancer in the United States. Current American Joint Committee on Cancer (AJCC) staging uses Breslow depth and ulceration as the two primary tumor factors that predict metastatic risk in cutaneous melanoma. Early disease stages are generally associated with high survival rates. However, in some cases, patients with thin melanomas develop advanced disease, suggesting other factors may contribute to the metastatic potential of an individual patient’s melanoma. This review focuses on the role of the lymphatic system in the metastasis of cutaneous melanoma, from recent discoveries in mechanisms of lymphangiogenesis to elements of the lymphatic system that ultimately may aid clinicians in determining which patients are at highest risk. Ultimately, this review highlights the need to integrate pathological, morphological, and molecular characteristics of lymphatics into a “biomarker” for metastatic potential.

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.

Lymphatic transit rate as a predictive parameter for nodal metastasis in primary limb malignant melanoma

BACKGROUND

The status of sentinel lymph node (SLN) is one of the most predictive prognostic factors in patients with clinically localized malignant melanomas (MMs). However, since the positive SLN metastatic rate is as low as 20%, it is desirable to minimize SLN biopsy performance with imaging. By dynamic lymphoscintigraphy, we have proposed the lymphatic transit rate (LTR), the value that the distance between the primary lesion and SLN is divided by scintigraphic saturation time. LTR represents the scintigraphic saturation velocity and can be used for evaluation of metastasis of skin cancers.

METHODS

Dynamic lymphoscintigraphy data from 36 lymph nodes in 36 patients with primary MM on the limb were analyzed. The initial sites of the MMs were the lower limb in 24 patients and the upper limb in 12 patients. Histopathologically, nodal metastasis was found in 10 patients.

RESULTS

In the lower limb MM, the mean LTRs were 3.49 cm/min in histologically non-metastatic SLNs and 4.49 cm/min in histologically metastatic SLNs (P = 0.0056). In the upper limb MM, the mean LTRs were 2.59 cm/min in non-metastatic SLNs and 3.94 cm/min in metastatic SLNs (P = 0.0162). Thus, significantly higher LTRs were obtained in the metastatic SLNs. All SLNs with LTR < 4.0 cm/min in the lower limb MM and those with LTR < 3.0 cm/min in the upper limb MM were non-metastatic.

CONCLUSION

LTR is a useful predictive indicator for nodal metastasis and SLN biopsy performance in MMs.