Unusual cutaneous Langerhans cell sarcoma without extracutaneous involvement.

Langerhans cell sarcoma (LCS) typically presents as cytologic atypia and clinical aggressiveness and may involve multiple organs during the progression of the disease. Primary skin LCS without any extra-cutaneous site association is extremely rare and only a few such cases have been described in the literature. We present a case of unusual primary LCS in skin occurring in a middle-aged male patient. Physical examination revealed a large ulcerated cutaneous lesion and a smaller nodular lesion were located in the skin of the extensor side of his right knee. There was no regional lymph node or any other extra-cutaneous organ involvement. Histologically, typical large and pleomorphological tumor cells with epithelioid appearance and significantly malignant cytological features were observed to infiltrate in dermis and subcutaneous tissue. By immunohistochemistry, the tumor cells were positive for CD1a, S-100 protein and largerin strongly and diffusely. However, these cells were negative for CD3, CD20, CD21, pan-cytokeratin, HMB-45, Melan-A, and MPO. A diagnosis of primary cutaneous LCS was made. The patient received systemic chemotherapy of CHOP regimen, and was on a regular follow-up period for 12 months. There was no sign of relapse of tumor or any other extra-cutaneous organ involvement by whole body positron emission tomography/computed tomography (PET/CT) study. Because LCS is a high-grade malignancy with poor prognosis, it suggests that strict histological analysis and thorough radiographic examination are necessary for accurately diagnosing this tumor even if cutaneous involvement presented only. VIRTUAL SLIDES: http://www.diagnosticpathology.diagnomx.eu/vs/6527428618381393.