Signet-Ring Cutaneous Squamous Cell Carcinoma Arising on the Back of the Finger
An 83-year-old man presented with a skin lesion on his left hand. He had no medical history of note. He first noticed the skin lesion 3 years ago and it had gradually enlarged. Physical examination revealed a 31 × 21 mm, reddish-brown, erosive macule on the back of the left fourth finger (fig. ). Medical imaging, including PET/CT, could not detect any other neoplastic lesions on the body. A biopsy taken from the lesion showed a thickened epidermis with parakeratosis, but no granular layer. We also observed an abnormal stratified arrangement, cytologically atypical keratinocytes (fig. ) and an inflammatory cell infiltrate in the dermis. Notably, numerous signet-ring cells with crescentically compressed nuclei were seen extending to the cellular border (fig. ). The results of mucicarmine and periodic-acid Schiff staining were both negative. Based on these findings, a histological diagnosis of solar keratosis, which was expected to advance to SCC, was made. The lesion was therefore excised with a 5-mm margin and the wound was covered by a skin graft.\nHistological examination of the whole tumor revealed irregular masses of proliferating tumor cells with invasive, atypical epidermal keratinocytes. Horn pearl cells and cells with individual keratinization were also present. The border of the lesion showed focal parakeratosis and a loss of normal epidermal stratification. Signet-ring cells were present, both at the border and throughout the tumor (fig. ). Immunohistochemistry revealed that the tumor cells were negative for CK20, carcinoembryonic antigen, vimentin, HMB45, Melan A and desmin. A final diagnosis of signet-ring SCC was made. The patient has been monitored for 3 years, but no recurrence has been noted to date.