A 39-year-old woman was referred to our center by a laryngologist for further diagnostics due to conductive hearing loss, with no other abnormalities in the laryngologic examination. Laboratory test results were unremarkable. Magnetic resonance imaging of the middle ear revealed an irregular, focal, intensely contrast-enhanced lesion with features of diffusion limitation (Figure 1A) on the left side, at the level of the promontory. The lesion extended to the eustachian tube, closing its opening, and was accompanied by massive secondary effusion within the cells of the mastoid process (Figure 1B). Computed tomography (CT) excluded bone destruction of the scutum, auditory ossicles, and bony labyrinth (Figure 1C).

Figure 1. A – magnetic resonance imaging scan (contrast-enhanced T1-weighted image) showing a lesion in the middle ear with intense contrast enhancement (arrow); B – magnetic resonance imaging scan (T2-weighted image) showing massive effusion within the mastoid cells (arrow); C – computed tomography of the temporal bone showing a lesion in the middle ear without ossicular chain erosion (arrow); D – histopathologic analysis showing an infiltrate composed of monomorphic cells forming rosettes and nest-like structures (hematoxylin and eosin staining, magnification × 200); E, F – immunohistochemical staining positive for synaptophysin (E) and chromogranin (F), magnification × 200

Due to a suspicion of malignancy, the patient was scheduled for an urgent operation. A tumor of the tympanic cavity and mastoid process on the left side was removed. Histopathologic analysis showed that it was composed of a homogeneous population of cells forming rosettes, single solid fields, and tubules filled with mucus (mucicarmine-positive) (Figure 1D). Angioinvasion and perineural infiltration were not detected. The cancer cells expressed synaptophysin, chromogranin, CD56, cytokeratin (CK) AE1/AE3, and focally CK7 (Figure 1E and 1F). The tumor exhibited low mitotic activity; mitotic index was 1/10 high-power fields, and Ki-67 was 2%. According to the 2019 World Health Organization classification of neuroendocrine tumors (NETs), the tumor was classified as middle ear NET G1 (MeNET G1). Due to diagnostic difficulties, the histologic sample was consulted in another center, where the diagnosis was confirmed.

No signs of distant spread were detected on a CT scan of the chest, abdominal cavity, and pelvis. The patient remains under surveillance in our clinic.

NETs are rare cancers that mainly develop in the digestive system and lungs. MeNETs constitute less than 2% of primary ear tumors.1 The most common symptoms are unilateral hearing loss and tinnitus, less frequently pain, discharge from the ear, or facial nerve palsy.1,2 MeNETs usually surround the ossicular chain without destroying it. Perforation of the eardrum with tumor spread to the ear canal occurs sporadically, as does destruction of the surrounding bone.3

Immunohistochemical staining for chromogranin A, synaptophysin, and CD56 is necessary to confirm the histopathologic diagnosis. Ki-67 proliferation and mitotic indexes are required for NET grading. Hence, they are essential in prognosis evaluation and therapeutic decision-making.3,4

In the available literature, cholesteatoma was often the first suspicion in patients with such a clinical presentation. In our case, it was paraganglioma, which is also considered in the differential diagnosis due to its very strong vascularization.2 Studies describe MeNET as a low-grade malignant lesion with rare local recurrences and distant metastases.5

The primary treatment method is complete surgical resection. Adjuvant treatment is not recommended. Some authors propose that radiotherapy and chemotherapy be used as postoperative adjuvant treatment when complete resection is not possible. After surgery, long-term follow-up is recommended due to slow tumor progression and difficulties in resection with wide margins.5