Sinus histiocytosis mimicking metastatic melanoma in lymph nodes of a patient with a large joint prosthesis: case report and review of the literature.

Malignant melanoma metastases to regional lymph nodes may be mimicked by several non-neoplastic processes, including sinus histiocytosis induced by fragments shed from joint prostheses. A patient who had an elective lymph node dissection for malignant melanoma and was found to have "post-prosthesis lymph node histiocytosis" resembling metastatic disease is described. Knowledge of the patient's past history of a total shoulder joint replacement along with the use of polarized light microscopy to identify birefringent particles of prosthetic debris allows for an accurate histologic diagnosis.