Insights into Langerhans cell sarcoma: Focus on cutaneous Langerhans cell sarcoma

AIMS: Langerhans cell sarcoma (LCS) is a rare malignant neoplasm that relatively frequently presents with primary cutaneous involvement. Owing to its extreme rarity, it is necessary to characterize the clinicopathological features of cutaneous LCS. METHODS: We analysed the clinicopathological features of five cutaneous LCS cases from our institution and reviewed an additional 38 cutaneous LCS cases and 69 extracutaneous LCS cases from the literature. RESULTS: In our patients, disease progression exceeded 3 years in four patients (4/5, 80%) who were diagnosed with progressed cutaneous LCS, while one (1/5, 20%) experienced rapid progression within 2 months and was diagnosed with de novo cutaneous LCS. Tumour cells were medium to large in size, with atypical mitotic figures, and nuclear pleomorphism was noted in the former four patients; round-to-ovoid nuclei were seen in the latter one patient. Eosinophils were sparse and observed in four patients (4/5, 80%). S100, CD1a and Langerin expression were not consistently diffuse, with Langerin expressed in <5% of tumour cells in one patient (1/5, 20%) whose ultrastructural examination revealed Birbeck granules. In the combined cohort of 43 cutaneous LCS cases, 32 (74.42%) were progressed cutaneous LCS and 6 (13.95%) were de novo cutaneous LCS. The progressed cutaneous LCS cases exhibited higher rates of lymph node metastasis (56.25% vs. 0%; P = 0.021), a trend toward more frequent ulceration (43.75% vs. 0%; P = 0.067) and a higher Ki-67 proliferation index (P = 0.046). Compared with extracutaneous LCS cases, cutaneous LCS cases demonstrated a malignant transformation course (84.62% vs. 19.57%; P < 0.001) and tended to have a more favourable prognosis (P = 0.077). CONCLUSIONS: We summarize the clinicopathological features of cutaneous LCS. Recognition plays a crucial role in preventing misdiagnosis and guiding appropriate treatment.