We were pleased to read the article by Olcott C. and Strasnick B. titled “A blue middle ear mass: Cholesterol granuloma mimicking a glomus tumor and endolymphatic sac tumor”. Am J Otolaryngol. 2017;38(1):100–102 , which presents very important clinical observations. Based on our experience and the literature review, we would like to present some comments on this problem. The benign tumors of the temporal bone (TB) have been divided into three groups: cholesterol granuloma (CG), glomus tumor (GT) and endolymphatic sac tumor (ELST) . The differential diagnosis of these tumors includes choroid plexus papilloma, papillary ependymoma, middle ear adenoma, and metastatic carcinoma of the thyroid, kidney, prostate, lung and breast. Affected patients suffer hearing loss, vertigo, tinnitus, headaches, trigeminal neuralgia, diplopia, facial weakness and other problems. Cholesterol granuloma (CG) is the most common benign lesion of the temporal bone/petrous apex (TB/PA). CG is a chronic inflammatory process consisting of granulation tissue and fibrous tissue with hemorrhage, and elongated clefts of cholesterol crystals surrounded by multinucleated giant cells, macrophages and accumulations of hemosiderin pigment. The cholesterol crystals stimulate the reaction and accumulation of giant cells, which are responsible for the tissue reaction . In theory by Jackler et al. that pneumatization of the temporal bone exposes marrow. Resulting degradation of hemosiderin is an inflammatory granulomatous reaction . GT has classic organoid (zellballen) or nesting pattern, without papillary-cystic structure and typical immunohistochemical antigenic profile.
ELST is a glandular-papillary tumor. It is composed of intracystic papillary proliferations lined by a single layer of columnar cells. The epithelial cells show slight variability in size and shape, and have a pale eosinophilic or clear cytoplasm. The nuclei are at the same level, often near the apical surface of the papillae. Mitotic activity is uncommon. The fibrous stroma is chronically inflamed and rich in small vessels approaching the epithelium. Fig. 1 Choroid plexus papilloma may be histologically very similar to ELST, but it arises within the ventricular system and does not invade bone. Temporal bone CT/MRI and histological examination help in an accurate diagnosis. GT is hypointense on MRI T1 and enhances with gadolinium, MRI T2 shows hyperintense. ELST enhances on CT, MRI T1 shows hyperintense with gadolinium enhancement, on MRI T2 is heterogenous. CG on MRI are iso- to hypointense on T1-weighted imaging, hyperintense on T2-weighted imaging, and non-enhancement with gadolinium . Information from the pathologist is very useful and can decide the extent of resection. The most extensive bleeding during the biopsy may occur in GT. In CG and ELSC bleeding is not that substantial. CG and ELST cause lysis of the strongest bones. Biopsy is the only way to diagnose definitively temporal bone tumors. Imaging is highly recommended before performing any deep tissue biopsies lesions of the middle ear. If results of initial biopsy are negative, we recommend performing deeper tissue biopsies.
