An overlooked site of tissue mast cells--the human tympanic membrane. Implications for middle ear affections.

The tympanic membranes of 14 deceased, with no record of ear disease in their medical files, were investigated with respect to the presence of mast cells. The Shrapnell membrane (pars flaccida) had a rich content of mast cells, whereas the pars tensa had none except for a few located close to blood vessels along the handle of the malleus. The volume density of the pars flaccida mast cells was calculated as 3.9% and the number of mast cells/mm2 as 299 +/- 35 (mean +/- SE; n = 14). The possible role of these mast cells under both healthy and diseased middle ear conditions is discussed.