Desmoplastic Melanoma

Spindle cell squamous cell carcinomas often present as ulcerated nodules on sun-exposed skin or on sites of prior ionizing radiation.^2,12 Like desmoplastic melanoma, spindle cell squamous cell carcinomas are characterized by spindle cells in the dermis. Helpful diagnostic clues may include evidence of squamous differentiation, including keratin pearls or overlying actinic keratosis (Figure 7). However, actinic keratosis is common on sun-damaged skin and cannot be used to definitively confirm this diagnosis. There also may be areas of the tumor with more typical epithelioid cells that are easily identified as squamous cell carcinoma.² Spindle cell squamous cell carcinoma stains positive for high–molecular weight cytokeratin antibodies and p63,² which can help to differentiate it from the other spindle cell tumors in the differential.

Figure 6. Spindle cells of leiomyosarcoma with cigar-shaped nuclei and adjacent glycogen vacuoles (H&E, original magnification ×600).		Figure 7. Spindle cell squamous cell carcinoma with overlying epidermal atypia that blends with the underlying dermal spindle cells (H&E, original magnification ×100).