Spindle cell/sclerosing rhabdomyosarcoma with intracranial invasion without destroying the bone of the skull base: a case report and literature review

Abstract

Spindle cell/sclerosing rhabdomyosarcoma (ssRMS) is a new subtype of rhabdomyosarcoma included in the World Health Organization soft tissue and bone tumor classification in 2013. Despite the increasing number of reported cases of ssRMS, the imaging characteristics of ssRMS are not established. Herein, we present the case of an elderly Japanese woman with ssRMS of the masticator space with intracranial invasion without destruction of the adjacent bone. Attention should be paid to the presence of intracranial infiltration that may indicate a worse prognosis. Tumor growth without bone destruction could be a key finding to differentiate ssRMSs from conventional subtypes of rhabdomyosarcoma.

Keywords: Soft-tissue neoplasms; head and neck neoplasms; magnetic resonance imaging (MRI); multi-detector computed tomography; rhabdomyosarcoma.

Fig. 1.

Coronal contrast-enhanced CT images showed that the mass consisted of two components; the extracranial component in the right masticator space (a; arrows) and the intracranial component in the right middle cranial fossa (a; arrowheads). The floor of the right middle cranial fossa showed bone sclerosis and thickening (b; arrow).

Fig. 2.

On axial T2W images, the extracranial component of the mass showed homogeneous mildly high intensity (a; arrow) compared to the muscles, and the intracranial component showed heterogeneous intensity (b; arrow) suggesting intratumoral necrotic or cystic changes. On axial T1W images, the intracranial component of the mass partially demonstrated high intensity (c; arrow) representing intratumoral hemorrhaging. On DWI obtained with b = 1000 s/mm², the solid area of the mass showed slightly high intensity (d; circle). The ADC value of the same area was 0.88 × 10⁻³mm²/s. On coronal contrast-enhanced fat-suppressed T1W images, the extracranial and intracranial components of the mass demonstrated heterogeneous and strong contrast enhancement. The coronal section through the foramen ovale shows the two components communicated with each other via the foramen ovale (e; arrow). On oblique MRA images, the extracranial component of the mass was fed by the deep temporal artery (f; arrow). The intracranial component of the mass was fed by the middle meningeal artery (f; arrowhead).

Fig. 3.

Hematoxylin and eosin (H&E) stain (×400 magnification) section showed that the tumor consisted of interlacing, fascicular proliferated spindle-shaped tumor cells and fibrocollagenous stroma (a). Rhabdomyoblast-like cells with cellular atypia were occasionally observed (b). On immunohistochemistry, desmin (c) and myogenin (d) were positive.

Fig. 4.

Site distribution of ssRMS in previously published cases (a). Head and neck and extremities are the most common sites of ssRMS. Age distribution (by decade) of SSRMS in the published cases (b). ssRMSs are diagnosed in a wide age range.