Rare Variant of Melanoma: Clinical, Histopathological and Prognostic Features in 5 Cases of Animal Type Melanoma

OBJECTIVE: Animal type melanoma is a rare variant of melanoma. Our aim was to report clinical, histopathological and prognostic features in our series with 5 cases of animal type melanoma.METHODS: Five cases with aminal type melanoma were included in the study. As clinical parameters age, gender, location of the lesion, lymph node involvement (sentinel or regional), duration of follow-up, development of satellite/in-transit/distant metastasis, and clinical stage were evaluated. As histopathological parameters cell type, Breslow thickness, Clark level, mitotic index, presence of ulceration, regression (partial/complete), lymphohistiocytic infiltration (absent/brisk/nonbrisk), and lymphovascular/perineural invasion were evaluated.RESULTS: Mean age of the patients was 61 ± 17 (39-79) and female/male ratio was 3/2. Three lesions (60%) were located on head and neck region and remaining 2 (40%) were located on acral region. Median lesion size was 2,5 cm (1,5-4 cm) and Breslow thickness was 7,5 mm (4-19 mm). All lesions had Clark level V. Cell types were epitheloid in 3 lesions (60%), spindle in 1 lesion (20%) and epitheloid and spindle in 1 lesion (20%). Ulceration, lymphovascular and perineural invasion was present in 3 (60%), 2 lesions (40%) and 1 lesion (20%) respectively. Lymphohistiocytic infiltration was present in 3 lesions (60%) (nonbrisk in 2 lesions, brisk in 1 lesion). Regression (partial) was observed in 1 lesion (20%). Mitotic index was ≥ 1 mm–2 in 3 lesions (60%). Regional lymph node metastasis was present in 2 (%40) cases and distant metastasis developed in 2 (%40) cases. CONCLUSION: In our series, animal type melanoma was observed between 4th-8th decades and both in females and males on head/neck or acral regions. In recent studies animal type melanoma has been reported to have a higher propensity to regional node metastasis but lower risk of distant metastasis compared to conventional melanoma. Similarly, lymph node involvement was high in our report, however distant metastasis rate was also high. In conclusion, further research is required about true biological potential of animal type melanoma.