Primary Dermal Melanoma (PDM): Histological and Clinical Interdependence to Guide Therapy

Background/purpose: This study examined clinical and histological parameters of primary dermal melanoma (PDM) to aid in its distinction from dermal metastasis. Methods: Retrospective analysis of a prospective cohort of PDM patients. Includes patients fulfilling the strict histologic criteria for PDM (N = 9) and patients who did not, but clinically, unequivocally had an intradermal melanoma—clinical PDM (cPDM; N = 17). Histopathology slides were re-examined. Prognosticators and outcome measures were compared between groups. Sentinel nodes’ retrieval and wide local excision (WLE) were offered to all patients as primary treatment. Results: 26 patients identified, 15 females with a median age of 69 years (range 3.5-85). Mean Breslow was 7.9 ± 5.7 mm (median 5.8, range 1.8-25.0), and the mean mitotic rate was 4.9 ± 3.8/mm² (median 4.0, range 0-17). Initial treatment and follow-up were as for cutaneous melanoma. One patient in each group with a palpable stage III underwent primary radical dissection. Sentinel nodes were retrieved in all 20 lymphatic mappings performed and found to be metastatic in 5 (25%) patients. Treatment consisted of completion lymph-node dissection. At a median postoperative follow-up of 62 months (range 8-132), 20 patients were disease-free, including 6 of 7 patients with stage III disease at presentation. Six patients died all of cPDM; 5 of 6 patients had primary ulcerated or epidermal-abutting melanomas. Conclusions: This is the first study to highlight cPDM. Diagnosis requires expert pathology review and a tight correlation to the clinical parameters. Patients seem to benefit from WLE with sentinel node retrieval and complete dissection when appropriate. However, clinical guidelines for dissection have changed since the time period of this retrospective review. Based on this series, complete nodal dissection in these melanomas is associated with better than expected outcome, for stage III disease.