Birbeck granules

Birbeck granules, also known as Birbeck bodies, are rod shaped or "tennis-racket" cytoplasmic organelles with a central linear density and a striated appearance. First described in 1961 (where they were simply termed "characteristic granules"), they are solely found in Langerhans cells. Although they are themselves part of normal Langerhans cell histology, they therefore provide a mechanism to differentiate Langerhans cell histiocytoses (which are a group of rare conditions collectively known as histiocytoses) from proliferative disorders caused by other cell lines.