Pigmented Squamous Cell Carcinoma of the Skin

Abstract

Melanoma is the most common malignant tumor in which melanin synthesis occurs, although other nonmelanocytic tumors synthesize melanin or contain nonneoplastic melanocytes. We present two cases of infiltrating pigmented squamous cell carcinoma of the skin and review the clinical, morphologic, and ultrastructural features. Melanin was found in epithelial tumor cells as well as in macrophages and dendritic melanocytes. Interestingly, one of the neoplasms was associated with an adjacent melanocytic nevus and pigmented solar keratosis. Immunohistochemical analysis showed that neoplastic cells stained for keratin and melanin-filled dendritic cells were found to be S-100 protein and HMB45 positive. A careless examination of the immunohistochemical stains for S-100 protein and HMB45 could cause the misdiagnosis of melanoma, a neoplasm that has a more ominous outlook.

Pigmented squamous cell carcinoma: case report and importance of differential diagnosis

“…The association of epithelial cells and melanocytes is usually found on skin, on skin appendages, and in a large number of malignant or benign tumors, which may cause difficulties in the differential diagnosis with melanoma. 5 …”

“…An hypothesis is that melanocytes derive from pluripotential stem cells in the hair matrix or even from neural crest cells. 5 …”

Cutaneous squamous cell carcinoma: a comprehensive clinicopathologic classification

“…In the most recent case series reported, the lesions presented as rapidly growing, crusted, pigmented papules on actinically damaged skin of elderly individuals 183,184 . Although most have occurred on the face, similar lesions have been described on the scrotum, in the oral mucosa, and on the conjunctiva and cornea 182,183 …”

“…Pigmented SCC is another rare variant which has been reported to represent as little as 0.01% to as great as 25% of all SCCs, with the higher percentages reported in the non‐English literature 182–184 . In the most recent case series reported, the lesions presented as rapidly growing, crusted, pigmented papules on actinically damaged skin of elderly individuals 183,184 .…”

Pigmented Bowen's Disease Clinically Mimicking Melanoma of the Nail

“…Factors causing neoplasia of keratinocytes may stimulate the proliferation of melanocytes 22 . It is also possible that dendritic melanocytes invaded by tumor discharge melanin granules which pervade the tumor and possibly become phagocytized by the tumor cells 23,24 . Regardless of etiology, the pigmentation has not been found to correlate with prognosis 9 …”