Middle Ear Cholesteatoma: This condition is characterized by a cyst or sac in the middle ear that contains dead skin cells and other debris, often appearing as a yellowish lesion behind the eardrum. It's a common cause of such symptoms due to its propensity to accumulate in the middle ear space.

Middle Ear Effusion: Fluid accumulation in the middle ear can sometimes appear yellowish due to the presence of pus or debris, especially if the effusion becomes infected. This condition is relatively common and can follow an upper respiratory infection.
Tympanosclerosis: This condition involves the deposition of collagen and calcium in the middle ear, which can appear as yellowish plaques on the eardrum or in the middle ear space. It often follows recurrent or chronic otitis media.

Glomus Jugulare Tumor: Although rare, this is a type of paraganglioma that can present as a yellowish mass behind the eardrum due to its vascularity. Missing this diagnosis could lead to significant morbidity due to its potential for local destruction and possibility of malignancy.
Middle Ear Cancer: Various types of cancer can present in the middle ear, and while extremely rare, they are critical not to miss due to their poor prognosis if not treated early.

Langerhans Cell Histiocytosis (LCH): This rare disorder can affect the temporal bone and present with a yellowish lesion behind the eardrum among other symptoms. It's part of a spectrum of diseases involving abnormal proliferation of Langerhans cells.
Middle Ear Lipoma: A benign tumor composed of fat tissue, which can appear as a yellowish lesion due to its fatty content. It's an uncommon finding in the middle ear.