A systematic review and meta-analysis of animal-type melanoma

Background Animal-type melanoma is a rare subtype of melanoma with heavily pigmented dermal epithelioid and spindled melanocytes. Its classification as a subtype of melanoma versus a borderline melanocytic tumor is debated. Objectives Our primary objective was to characterize the demographics, clinical presentation, histopathology, management, and outcomes of patients with animal-type melanoma. Methods We performed a systematic review and meta-analysis of the English-language literature on animal-type melanoma. Results We identified 190 cases of animal-type melanoma. They occurred equally in men and women, with Caucasians (53.7%) most commonly affected. The median Breslow depth was 3.8 mm; ulceration was reported present in 15.8%; and dermal mitoses greater than or equal to 1/mm² was reported in 27.4%. The most common initial management was wide local excision with sentinel lymph node biopsy (55.7%). In all, 78 patients underwent sentinel lymph node biopsy with 41.0% positivity rate. A total of 32 patients underwent completion lymph node dissection with 34.4% positivity rate. Locoregional recurrence was reported in 15 patients, recurrence with distant metastases in 6 patients, and death in 5 patients. Limitations Data were obtained from small studies with limited follow-up. There is no universally accepted definition of animal-type melanoma. Conclusion Prospective studies with complete staging information and molecular profiling may allow further characterization of this tumor.