CASE 14843 Published on 01.08.2017

Chondromyxoid fibroma of the mastoid

Section

Neuroradiology

Case Type

Clinical Cases

Authors

Nicolas De Vos1,2
David Creytens3
Mariėtte De Cock4
Filip Vanhoenacker1,2,5

1. Department of Radiology, Ghent University Hospital, Ghent University, Ghent
2. Department of Radiology, AZ Sint-Maarten Duffel-Mechelen
3. Department of Pathology, Ghent University Hospital, Ghent University, Ghent
4. Department of Otorhinolaryngology, AZ Sint-Maarten, Duffel-Mechelen
5. Department of Radiology, Antwerp University Hospital, Antwerp University, Antwerp
Patient

21 years, female

Categories
Area of Interest Head and neck, Education ; Imaging Technique MR, RIS, CT
Clinical History
A 21-year-old female patient presented at the emergency department with drooping of the left eyelid and left mouth corner. Neurological examination showed a left lower motor neuron facial nerve palsy. Otoscopy showed narrowing of the left external auditory canal.
Imaging Findings
Magnetic resonance imaging (MRI) demonstrated a space-occupying lesion in the mastoid portion of the left temporal bone. On T1-weighted imaging (T1-WI), the lesion was of low signal intensity (SI) (Fig. 1A). On T2-weighted imaging (T2-WI), the lesion displayed heterogeneous intermediate to high SI (Fig. 1B). Diffusion-weighted images and apparent diffusion coefficient maps showed no significant diffusion restriction (Fig. 2). After intravenous administration of gadolinium-based contrast medium, the lesion enhanced heterogeneously, with marked enhancement in the areas which were of intermediate SI on T2-WI, and absence of enhancement in the areas which were of high SI on T2-WI (Fig. 3)
Cone-beam computed tomography confirmed the presence of a destructive osteolytic space-occupying lesion in the left mastoid (Fig. 4). The lesion eroded the facial canal, explaining the facial nerve palsy of the patient. The lesion also extended into the external auditory canal, explaining narrowing of this canal on otoscopy.
Discussion
CMF is an uncommon benign bone tumour of cartilaginous origin [1, 2, 3]. It is usually found in the metaphyses of the long bones of the lower extremities, especially the proximal metaphysis of the tibia [4]. CMF is also seen in the flat bones and bones of hands and feet. There is a slight predilection in males and a peak incidence in the second and third decades. CMF is rarely encountered in the skull base and is extremely rare in the mastoid portion of the temporal bone [5, 6]. This case is only the eleventh identified in literature (Table 1).
Clinical perspective: Patients with CMF of the appendicular skeleton primarily complain of pain and soft tissue swelling. Symptoms of CMF of the mastoid include hearing loss [7-11], facial nerve palsy [4, 5, 12], otalgia [2, 4, 9], and vertigo [6, 8].
On plain radiographs, CMF of the appendicular skeleton is often seen as an eccentric radiolucent lesion with a well-defined sclerotic margin [13]. On MRI, CMF of the appendicular skeleton shows low SI on T1-WI and high SI on T2-WI. After intravenous administration of gadolinium-based contrast medium, peripheral nodular enhancement is seen in 70 % of lesions, while diffuse contrast enhancement is seen in 30% [14]. For CMF of the mastoid, (cone-beam) CT and MRI are helpful in elucidating bone and soft tissue extension, respectively. On (cone-beam) CT, CMF of the mastoid is seen as a destructive, osteolytic, space-occupying lesion. Intratumoural calcifications are more frequently seen in CMF of the mastoid compared to CMF of the appendicular skeleton. On MRI, CMF of the mastoid shows low SI on T1-WI and heterogeneous intermediate to high SI on T2-WI. This heterogeneity can be attributed to the varying composition of chondroid, myxoid, and fibrous elements. Sometimes, cystic or haemorrhagic foci are seen. After intravenous administration of gadolinium-based contrast medium, there is heterogeneous enhancement, with clear enhancement in the areas which show intermediate SI on T2-WI, and absence of enhancement in the areas which show high SI on T2-WI. The latter are probably composed of predominantly chondroid tissue.
Compared to CMF of the appendicular skeleton, CMF of the mastoid can occur at an older age, contains more intratumoral calcifications and shows more heterogeneous SI on T2-WI. Since both radiological and histopathological findings often show considerable overlap with other diseases, including endolymphatic sac tumours and malignant cartilaginous tumors, the diagnosis of CMF remains challenging.
Differential Diagnosis List
Chondromyxoid fibroma of the mastoid
Endolymphatic sac tumor
Chondroma and chondrosarcoma
Facial nerve schwannoma
Final Diagnosis
Chondromyxoid fibroma of the mastoid
Case information
URL: https://eurorad.org/case/14843
DOI: 10.1594/EURORAD/CASE.14843
ISSN: 1563-4086
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