Spindle cell carcinoma of the larynx with rhabdomyoblastic heterologous element: a rare form of divergent differentiation

Abstract

Spindle cell (sarcomatoid) carcinoma of the larynx is a rare subtype of squamous cell carcinoma that shows a prominent spindle cell component with a mesenchymal phenotype. Heterologous elements may be seen in these spindled areas and usually consist of osteosarcomatous or chondrosarcomatous differentiation. We describe an unusual spindle cell carcinoma of the vocal cord in a 68-year-old male which demonstrated rhabdomyosarcomatous differentiation as confirmed by desmin and myogenin immunoreactivity. Thus rhabdomyosarcomatous differentiation adds to the phenotypic spectrum of spindle cell carcinomas of the larynx and should be considered before invoking a diagnosis of true rhabdomyosarcoma of the larynx.

Fig. 1

a SPC demonstrating an invasive carcinomatous component embedded in a cellular stroma (Hematoxylin and Eosin, ×40). b The surface epithelium shows severe dysplasia/carcinoma in situ (Hematoxylin and Eosin, ×200). c The sarcomatoid component is comprised of primitive appearing stellate to spindle shaped cells with scant to moderate amount of cytoplasm, dispersed in a myxoid background. Note the sharp distinction between the carcinoma and sarcoma component and concentric condensation of spindle cells around the squamous nests (cambium-like zone) (Hematoxylin and Eosin, ×100). d The sarcomatous component shows pleomorphic plasmacytoid to elongated spindle cells with moderate amount of eosinophilic cytoplasm and eccentrically placed nuclei (“fetal-type rhabdomyoblasts”). Inset A few cells demonstrate cross striations (arrow) (Hematoxylin and Eosin, ×400)

Fig. 2

a, b The SPC demonstrates strong cytoplasmic staining with cytokeratin 5/6 (2a, ×400) and strong nuclear staining with p63 (2b, ×400) in the carcinomatous component. The sarcomatoid component immediately adjacent to the carcinomatous nests shows scattered cytokeratin 5/6 and p63 positive cells. c, d Some of the malignant spindle cells demonstrate strong cytoplasmic staining with desmin (2c, ×400) and strong nuclear staining with myogenin (2d, ×400)