Preoperative Screening CT and PET/CT Scanning for Acral Melanoma: Is it Necessary?

Recent advancements in the diagnosis and treatment of acral melanoma

Acral melanoma (AM) is the most common histologic subtype of melanoma in dark-skinned patients and is associated with a worse prognosis and a high mortality rate, largely due to the inconspicuous nature of early-stage lesions, which can lead to late diagnosis. Because of the overlapping clinical and histopathological features of AM with other forms of cutaneous melanomas, early detection of AM requires a multidisciplinary approach that integrates various diagnostic modalities, including clinical examination, dermoscopy, histopathology, molecular testing, radiological imaging, and blood tests. While surgery is the preferred method of treatment for AM, other therapeutic options may be employed based on the stage and underlying etiology of the disease. Immune checkpoint inhibitors, molecular targeted therapy, radiotherapy, chemotherapy, and oncolytic virotherapy represent promising advanced treatment options for AM. In this review, we provide an overview of the latest advancements in diagnostic and therapeutic methods for AM, highlighting the importance of early detection and the prompt, individualized management of this challenging disease.

Diagnostic value of 18 F-fluoro-2-deoxyglucose positron emission tomography/computed tomography imaging in acral melanoma-predominant Asian patients

BACKGROUND

Tumor staging is crucial for melanoma, of which acral melanoma is the predominant subtype in Asians. 18 F-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) and 18 F-FDG-PET/computed tomography ( 18 F-FDG-PET/CT) serve as noninvasive imaging tools for tumor staging. However, the literature is scarce on the diagnostic value of PET for acral melanoma.

METHODS

From January 1, 2006 to November 30, 2022, a total of 352 patients were diagnosed with melanoma at our hospital. Of them, 90 were diagnosed with cutaneous melanoma and underwent preoperative PET/CT for staging and sentinel lymph node biopsy or complete lymph node dissection. Staging of PET/CT was confirmed by histopathology or following imaging. The lymph node biopsy, distant metastasis status, and PET/CT imaging results were analyzed.

RESULTS

Of all the 90 patients with cutaneous melanoma, 72 of them were diagnosed as acral melanoma (80.0%). Compared with the histopathologic results, the lymph nodes were true-positive, true-negative, false-positive, and false-negative in 12, 54, 7, and 17 cases, respectively. The sensitivity of PET/CT for local lymph nodes was 41.4% (95% CI, 23.5%-61.1%), whereas its specificity was 88.5% (95% CI, 77.8%-95.3%). As for the detection of distal metastasis, the PET results were true-positive, true-negative, false-positive, and false-negative in 6, 65, 15, and 4 cases, respectively. The sensitivity of PET for distal metastasis detection was 60.0% (95% CI, 26.2%-87.8%), whereas its specificity was 81.3% (95% CI, 71.0%-89.1%).

CONCLUSION

Although noninvasive, PET/CT has relatively low sensitivity in regional lymph node evaluations, and fair sensitivity in distal metastasis detection in Asian patients with acral melanoma. Thus, PET/CT may be more useful in patients with clinically palpable nodes or more advanced disease stages.

18F-FDG PET/CT imaging of primary malignant melanoma of rectum with liver metastases mimicking rectum cancer: case report and literature review

Malignant melanoma (MM) is an aggressive malignant tumor, which mostly occurs on the skin, uvea, etc. The mucosal MM accounts for a small proportion of all MM and can occur in the digestive tract. Primary MM of the digestive tract is rare and can be found in the middle and lower third of the esophagus and the rectum containing melanocytes. Primary rectal MM often occurs in middle-aged and elderly women, with rapid progress and strong invasion. We report a case of a 61-year-old man diagnosed with primary malignant melanoma of the rectum with liver metastases mimicking rectum cancer. ¹⁸F-FDG PET/CT showed the rectal wall was markedly thickened with a high metabolic level (SUVmax 10.6) and the boundary between the lesions and the prostate was unclear. In addition, increased FDG uptake were found in multiple lymph nodes, lung, liver, and bones, suggesting metastasis. In this case, ¹⁸F-FDG PET/CT shows the advantage of evaluating the whole-body situation and provides valuable information for the diagnosis, tumor stage, evaluation of treatment efficacy, and prognosis of MM.