[Langerhans cell sarcoma: a clinicopathologic analysis of four cases]

Objective: To investigate the clinicopathological features, differential diagnosis, and genetic alteration of Langerhans cell sarcoma (LCS). Methods: Four cases of LCS were collected from Fujian Provincial Hospital and Fuzhou General Hospital of Nanjing Military Command of PLA from July 2013 to January 2017. Clinicopathological features and immunophenotype were retrospectively reviewed in four LCS cases combined with genetic mutation analysis of BRAF and ALK. Results: Four cases included 2 women and 2 men with ages from 42 to 79 years (median=59.3 years). The size of the tumors ranged from 2.5-7.8 cm. Histologically, at the low power field, the tumors consisted of highly cellular proliferation in fascicules, whirlpool and diffuse sheets arrangement. The tumor cells were kidney-or horseshoe-shaped to round epithelioid cells or enlarged spindle cells. The neoplastic cells showed cytological atypia, hyperchromatic nuclei with prominent 1 to 2 nucleoli. Multinucleated giant cells were also found. Mitotic activity was approximately (50-70) mitoses/10 HPF. Immunohistochemically, the tumor cells were positive for S-100 protein (4/4), SOX10(3/4), Langerin/CD207(4/4), CD1a(3/4), CD68(3/4), CD163(3/4), and INI-1(4/4). Ki-67 index was 30%-80%. Gene mutation analysis showed that one case had BRAF V600E mutation but none had ALK gene alteration. Conclusions: LCS is a rare tumor with highly malignant potential and distinct morphologic features.The primary treatment for LCS is completely surgical excision and chemotherapy. The prognosis is generally poor.