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Objective: To explore the feasibility of an intraoperative navigation technology based on preoperatively acquired single photon emission computed tomography combined with computed tomography (SPECT/CT) images during sentinel node (SN) biopsy in patients with melanoma or Merkel cell carcinoma., Materials and Methods: Patients with a melanoma (n=4) or Merkel cell carcinoma (n=1) of a lower extremity scheduled for wide re-excision of the primary lesion site and SN biopsy were studied. Following a Tc-nanocolloid injection and lymphoscintigraphy, SPECT/CT images were acquired with a reference target (ReTp) fixed on the leg or the iliac spine. Intraoperatively, a sterile ReTp was placed at the same site to enable SPECT/CT-based mixed-reality navigation of a gamma ray detection probe also containing a reference target (ReTgp).The accuracy of the navigation procedure was determined in the coronal plane (x, y-axis) by measuring the discrepancy between standard gamma probe-based SN localization and mixed-reality-based navigation to the SN. To determine the depth accuracy (z-axis), the depth estimation provided by the navigation system was compared to the skin surface-to-node distance measured in the computed tomography component of the SPECT/CT images., Results: In four of five patients, it was possible to navigate towards the preoperatively defined SN. The average navigational error was 8.0 mm in the sagittal direction and 8.5 mm in the coronal direction. Intraoperative sterile ReTp positioning and tissue movement during surgery exerted a distinct influence on the accuracy of navigation., Conclusion: Intraoperative navigation during melanoma or Merkel cell carcinoma surgery is feasible and can provide the surgeon with an interactive 3D roadmap towards the SN or SNs in the groin. However, further technical optimization of the modality is required before this technology can become routine practice.

Objectives: Merkel cell carcinoma (MCC) is a rare aggressive skin tumor associated with a high mortality rate. The present study evaluated the role of fluorine-18 fluorodeoxyglucose (F-FDG) PET/computed tomography (CT) in subsequent management of patients with MCC., Methods: A total of 101 consecutive F-FDG PET/CT studies of 46 patients with MCC (28 men, 68±15.4 years) were retrospectively evaluated and the role in clinical care was documented., Results: There were 40 positive studies (40%) in 28 patients (61%); of these, 33 studies (33%) in 27 patients (59%) showed metastatic disease. Fifty-two PET/CT studies (51%) in 23/46 (50%) patients were negative. Fifty-three studies (52%) were performed for staging or restaging in 41 patients, 29 scans (29%) were performed for routine follow-up in 10 patients, nine studies were carried out for suspected recurrent disease in eight patients, and 10 studies were carried out for assessment of response to therapy in seven patients. On the basis of PET/CT results, there was a change in disease stage in 12 studies in 12 patients (26%) and further change in the management of seven patients (15%). Overall, 2/29 routine follow-up studies were positive with further impact on management in one patient., Conclusion: F-FDG PET-CT altered the stage of one of four patients and changed the management of one of seven MCC patients. In the majority of patients, a negative F-FDG PET-CT study excluded active MCC with a high degree of confidence. PET-CT contributed toward patient management when performed for staging and restaging, monitoring response to treatment, and suspected recurrent disease, but not in the routine follow-up of asymptomatic patients with MCC.

Objectives: Sentinel lymph node mapping has a long history of successful use in the staging and management of cutaneous melanoma. Most practitioners inject the primary site with radiocolloid the evening before or on the day of lymphoscintigraphy. We have found that imaging the day after lymphoscintigraphic injection is quite feasible; it decreases background radioactivity and makes scheduling easier. We aimed to determine whether 2-day lymphoscintigraphy is as effective at defining nodes as 1-day lymphoscintigraphy., Materials and Methods: We reviewed the records of 172 patients who underwent lymphoscintigraphy over a 6-year period, all of whom had a diagnosis of melanoma and had undergone 2-day lymphoscintigraphy with imaging on both the day of injection and the day immediately after. The number of basins and the basin pattern were then examined when a discrepancy was seen in the reports in order to decide whether an actual discrepancy between images was present. The number of nodes on same-day and next-day imaging was then evaluated as well., Results: On same-day imaging, the number of basins identified was three node basins (NBs) in five patients, two NBs in 42 patients, one NB in 123 patients and no NB in two patients. On next-day imaging, the number of basins identified was three NBs in five patients, two NBs in 36 patients, one NB in 129 patients and no NB in two patients. The difference in the number of basins between same-day and next-day imaging was not significant once cases such as iliac, para-aortic and pelvic nodes, which do not affect surgical planning, were excluded (P=0.08). The pattern of nodes within the basin was also examined, and the presence or disappearance of disappearing nodes correlated with timing of the next-day images. All cases of disappearing nodes occurred at least 19 h after injection, and cases of disappearance of significant nodes occurred at at least 22 h. The absolute number of nodes declined in 45 cases, remained the same in 124 and increased in three., Conclusion: Overall, the same number of basins and, usually, nodes can be detected on the day after injection, as long as the time after injection does not significantly exceed 19 h.

Purpose: Merkel cell carcinomas (MCC) are neuroendocrine skin tumours frequently responsible for lymph node recurrence and metastatic disease and for which optimal management remains to be defined. The objective of this study was to evaluate the impact of (18)F-fluorodeoxyglucose ((18)F-FDG)-PET/computed tomography (CT) on the staging and treatment of MCC patients., Materials and Methods: Twenty-three patients with a histologic diagnosis of MCC explored by (18)F-FDG-PET/CT between 2004 and 2012 were retrospectively included in the study. The detection of new lesions and the change in tumour staging and treatment were evaluated. For each patient, the (18)F-FDG-PET/CT results were compared with histological, clinical and imaging data., Results: Sixty-six (18)F-FDG-PET/CT scans were performed at initial presentation (n=18), during subsequent monitoring (n=34) or during evaluation of chemotherapy response (n=14). The sensitivity, specificity and positive and negative predictive values of the (18)F-FDG-PET/CT were 97, 89, 94 and 94%, respectively. Two false-positive results (lymphadenitis) and one false-negative result (regional metastatic lymph nodes) were accounted for. Lesions not detected clinically or by conventional imaging techniques were found in 44% of the 52 (18)F-FDG-PET/CTs performed at initial presentation and subsequent monitoring, with, respectively, 50 and 41% of scans identifying new lesions. At initial presentation, (18)F-FDG-PET/CT led to a change in tumour staging in 39% of patients. Patient management was modified by (18)F-FDG-PET/CT results in one-third of patients (33% of patients at initial presentation, 32% during subsequent monitoring and 36% during evaluation of chemotherapy response). F-FDG-PET/CT incidentally detected four additional histologically confirmed cancers., Conclusion: This retrospective study confirms the important impact of (18)F-FDG-PET/CT on the management of MCC patients.