%0 Journal Article %T Unusual cutaneous Langerhans cell sarcoma without extracutaneous involvement %A Yang Li %A Bin Li %A Xiao-ying Tian %A Zhi Li %J Diagnostic Pathology %D 2013 %I BioMed Central %R 10.1186/1746-1596-8-20 %X http://www.diagnosticpathology.diagnomx.eu/vs/6527428618381393 webciteAccording to the degree of cytologic atypia and clinical aggressiveness, Langerhans cell tumors are divided into two main subgroups: Langerhans cell histiocytosis (LCH) and Langerhans cell sarcoma (LCS) [1]. LCS is a rare high-grade neoplasm with overtly malignant cytologic features and aggressive clinical course. It can occur at any age and may involve multiple systems or tissues. Skin and underlying soft tissue are the most common involvement, but other unusual locations, such as bone [2], lung [3], gallbladder and peritoneal lymph nodes [4] have also been described in the literature. LCS may be limited to cutaneous involvement or may progress to affect other organs. However, to our knowledge, primary cutaneous LCS without any extra-cutaneous association is extremely rare and so far only a few such cases with immunohistochemical and/or ultrastructural confirmation have been described in the literature [5,6]. Due to its rareness in skin, the accurate diagnosis of cutaneous LCS could be difficult to be made because similar microscopic features may be encountered in metastatic cancer, malignant melanoma, anaplastic large cell lymphoma and myeloid sarcoma. Therefore, it is indeed a challenge for clinicians to make a correct diagnosis when the LCS presents as a solitary cutaneous mass because inaccurate diagnosis may lead to improper treatment. Herein we describe an additional case of primary cutaneous LCS arising in the skin in a middle-aged male patient without any extra-cutaneous manifestation in order to provide valuable information in this field.A 48-year-old Chinese male visited his local hospital in May 2010 with a gradually enlarged and ulcerated erythematous plaque on his right knee. The patient stated that the lesion had been presented on the extensor side of his right knee for approximately 6 months and treated with a steroid ointment initially. However, the lesion gradually enlarged and u %K Langerhans cell sarcoma (LCS) %K Langerhans cell tumor %K Cutaneous involvement %K Differential diagnosis %U http://www.diagnosticpathology.org/content/8/1/20