Spindle cell tumours are uncommon and can be due to a variety of malignancies:
- Carcinoma with spindle cell differentiation (e.g. spindle cell carcinoma, often seen the lung or other sites)
- Melanoma which consists of spindle cells (e.g. desmoplastic/neurotropic melanoma, but also other types)
- Soft tissue sarcoma - most sarcomas can contain spindle cell areas
Carcinomas are vastly more common than sarcoma; therefore a spindle cell tumour in a site commonly involved by carcinoma (e.g. the skin) makes diagnosis complicated! Alternatively, a deeply seated tumour arising within a muscle compartment is highly unlikely to be a carcinoma, except in the rare case of a metastasis from a carcinoma.