Desmoplastic melanoma: A 12-year experience with sentinel lymph node biopsy
Introduction
Melanoma is a highly aggressive form of skin cancer. According to the American Cancer Society, over 70,000 new cases are expected in 2011 with a mortality rate of approximately 13%.1 Multiple studies have demonstrated that involvement of the local lymph nodes is one of the most important prognostic indicators regarding the course of the disease.2, 3, 4 Excisional biopsy of the sentinal lymph nodes (SLN), the first lymph nodes draining the tumor along its lymphatic pathway, and examination of these nodes for metastatic cells is an appropriate way of predicting the probability of additional melanoma in the remaining nodes in that lymphatic-draining basin.5, 6 At present, patients with melanomas greater than 1 mm in depth are advised to undergo sentinel lymph node biopsy (SLNB) with subsequent completion lymphadenectomy (CL) if tumor is found in the SLN.7
Desmoplastic melanoma (DM) is often amelanotic (Fig. 1), highly infiltrative, and has a greater potential to recur than conventional melanoma. While sun-exposed areas of the body are most often involved, other body sites and mucosal surfaces may also be affected. The diagnosis of DM is based on histologic examination showing an ill-defined proliferation of spindle cells with cellular atypia embedded in sclerotic collagenous stroma. Confirmation by immunohistochemical staining for S-100 and other markers such as p75 NFGR is imperative.8, 9
At present, the decision whether or not to perform SLNB in patients with desmoplastic melanoma is still not resolved considering the opposing views in the literature regarding the incidence of nodal involvement in this particular histologic subtype.10, 11, 12, 13
Thus, given the paucity of data regarding nodal involvement in DM, we decided to review the incidence of nodal metastasis in our patients with DM at the Yale Melanoma Unit to better define guidelines regarding the performance of SLNB in this specific melanoma subtype (Fig. 2).
Section snippets
Methods
Using a prospectively maintained database, we reviewed all patients who underwent treatment for melanoma at the Yale Melanoma Unit in the twelve-year period between 1998 and 2010, during which a total of 3531 cases were treated. We identified 24 patients (0.7%) diagnosed with DM, 22 of whom underwent SLNB (Table 1). These patients' records were studied for clinical and histologic parameters, as well as clinical outcomes. DM patients were sub-classified according to Busam et al.14 and Hawkins
Results
Data analysis of the 24 DM patients revealed that 71% were over 60 years of age, with a higher incidence of males in this group of patients (M:F ratio 3:1). The head and neck was the most common anatomic area affected (67%), followed by the trunk (25%) and the upper extremities (8%). The majority of patients presented with high risk primary tumors: 88% had Clark level IV or V disease and 67% had Breslow thickness > 2 mm. Two patients from this group of 24 patients diagnosed with DM were
Discussion
Desmoplastic melanoma is a rare and atypical variant of cutaneous melanoma. Frequently amelanotic, it can present as a plaque or papule which often leads to an initial clinical misdiagnosis16 (Fig. 1). DM is commonly mistaken for a benign dermal tumor, an inflammatory condition, or carcinoma.
Initial studies on DM reported recurrence rates as high as 40–60%.17, 18, 19 However, when adjustments were made for tumor thickness, it was found that while local recurrence remained higher than in other
Conclusions
We determined that the incidence of SLN metastasis in our series of patients with DM is similar to most cutaneous variants. However, patients with mixed DM subtype have a higher rate of nodal metastasis (25%) as opposed to patients with pure DM (14%). While other authors have reported that patients diagnosed with pure DM were less likely to have a positive SLN than those patients with the mixed DM subtype (2% vs 16%), and therefore should not undergo SLNB,28 our findings of relatively high
Acknowledgments
This investigation was supported in part by NIH Research Grant CA-16359 from the National Cancer Institute and the Yale SPORE in Skin Cancer funded by the National Cancer Institute grant number 1 P50 CA121974 (R. Halaban, PI). The funding organization and sponsor had no direct role in the study design, in the collection, analysis and interpretation of data; in the writing of the manuscript; and in the decision to submit the manuscript for publication.
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