Granulation Tissue-Like Spindle Cell Squamous Cell Carcinoma of the Skin Arising in a Burn Scar.

Cutaneous spindle cell squamous cell carcinoma (SCSCC) is known to mimic malignant spindle cell neoplasms. In the head and neck region, a deceptively bland, granulation tissue-like pattern has also been reported that may simulate benign reactive processes; however, it has rarely been described in cutaneous SCSCC. Here, we report a case of cutaneous SCSCC with a granulation tissue-like spindle cell component arising from an upper arm burn scar in a 66-year-old woman. Histological examination of the punch biopsy specimen initially revealed a deceptively bland, yet atypical spindle cell proliferation with focal slit-like pseudovascular spaces, suggesting granulation tissue. Given the presence of a clinically ulcerated mass measuring 3.5 × 2.7 cm arising from a chronic scar, immunohistochemical analysis was performed, which supported the diagnosis of SCSCC, showing diffuse positivity for CK5 and p40 with p53 overexpression. Examination of the surgical specimen revealed morphological heterogeneity, with areas of conventional SCC and spindle cell components, including deceptively bland, granulation tissue-like areas and areas exhibiting myxoid change and overt cytologic atypia. This case highlights that cutaneous SCSCC may exhibit deceptively bland cytology closely mimicking granulation tissue, representing a potential diagnostic pitfall, particularly in limited biopsy specimens.