D. Spindle cell rhabdomyosarcoma
Rhabdomyosarcoma is a rare, aggressive, soft-tissue malignant tumor originating from undifferentiated striated skeletal muscle. Spindle cell/sclerosing rhabdomyosarcoma (SCSR) is one of 4 subtypes of rhabdomyosarcoma (embryonal, alveolar, pleomorphic, and SCSR) classified by the World Health Organization since 2013.1 Because SCSR is a newly classified and rare subtype, there is limited literature addressing risk factors, treatments, and prognosis. Spindle cell/sclerosing rhabdomyosarcoma makes up 5% to 13% of all rhabdomyosarcoma cases and is more common in adults, unlike embryonal and alveolar rhabdomyosarcoma, which are seen predominantly in children.2
The head and neck is the most common site of rhabdomyosarcoma, with an incidence rate of fewer than 1 case per 2 million people per year, making up 35% of all rhabdomyosarcoma cases.3 Within the head and neck, rhabdomyosarcoma can be classified into orbital, parameningeal (ie, ear, mastoid, nasal cavity, paranasal sinuses, infratemporal fossa, pterygopalatine fossa), and nonorbital nonparameningeal (ie, palate, parotid, tongue, any other head and neck sites) types.3 Parameningeal tumors, as in this patient, have the worst 5-year relative survival rate (49.1%) of any type and are more likely to present with regional or distant metastases, especially in adults.3 Parameningeal rhabdomyosarcoma, specifically of the infratemporal fossa in adults, has limited literature owing to its rarity.4