Electron microscopy of the lesion demonstrates tennis racket-shaped cytoplasmic structures in the malignant cells
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Electron microscopy of the lesion demonstrates tennis racket-shaped cytoplasmic structures in the malignant cells
The Birbeck granule was originally identified in Langerhans cells of the skin, then in adult pulmonary LCH, and later in cutaneous and bone lesions of childhood. The structure forms where the C-type lectin Langerin (CD207) accumulates and the Birbeck granule appears to be related to endosomal trafficking. The use of Langerin immunostain has largely supplanted the need for ultrastructural analysis. The Birbeck granule is a rod-shaped bilaminar disk with an internal zipper-like pattern of striations, often with a bulbous dilatation at one end, like a tennis racquet. The granules are found wherever Langerhans cells are seen in the body but are not unique to Langerhans cells and have been described in other cells (Fig. 19.15). LCH cells have few cytoplasmic organelles and filopodia at the cell surface.