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Cutaneous pigmented invasive squamous cell carcinoma: a case report with dermatoscopy and histology

Cutaneous invasive pigmented squamous cell carcinoma (SCC) is rare. There have previously been only a few case reports or small case series in the English literature [1–13]. 
 
In the largest published study there were five cases of pigmented invasive SCC in 46,791 archived cases of invasive SCC (approximately 0.01%) [2]. This compares to pigmented SCC in-situ (pigmented Bowen’s disease) in which the largest study found 52 of 951 (5.5%) consecutive cases of SCC in-situ to be pigmented [14]. 
 
The differential diagnosis of pigmented invasive SCC includes benign and malignant melanocytic neoplasms (melanoma and nevus) as well as pigmented types of benign and malignant epithelial neoplasms such as basal cell carcinoma (BCC), actinic keratosis (AK), SCC in-situ, seborrheic keratosis and melanoacanthoma [1, 12]. 
 
Our search has revealed five cases of pigmented invasive SCC with a description of dermatoscopy features [1, 9, 10, 12, 13] and in none of those cases was the diagnosis predicted.

In the largest published study there were five cases of pigmented invasive SCC in 46,791 archived cases of invasive SCC (approximately 0.01%) [2]. This compares to pigmented SCC in-situ (pigmented Bowen's disease) in which the largest study found 52 of 951 (5.5%) consecutive cases of SCC in-situ to be pigmented [14].
The differential diagnosis of pigmented invasive SCC includes benign and malignant melanocytic neoplasms (melanoma and nevus) as well as pigmented types of benign and malignant epithelial neoplasms such as basal cell carcinoma (BCC), actinic keratosis (AK), SCC in-situ, seborrheic keratosis and melanoacanthoma [1,12].
Our search has revealed five cases of pigmented invasive SCC with a description of dermatoscopy features [1,9,10,12,13] and in none of those cases was the diagnosis predicted.

Case report
An 80 year-old man with Fitzpatrick type 2 skin, presented for a routine skin check. A new raised pigmented skin lesion 6 mm in diameter was discovered on his right cheek denser blue pigment partially obscured the vessels. As an additional clue two white circles were present dermatoscopically (arrows, Figure 2). The peripheral borders of the lesion blended into peri-lesional skin without sharp demarcation.
The lesion was excised in toto. It was signed out by the reporting pathologist as a "focally pigmented, moderately well differentiated acantholytic squamous cell carcinoma extending to mid-dermis." (Figures 3-5).     The authors advised about the presence of ulceration but this is not evident in the dermatoscopic image. They considered the differential diagnosis of melanoma and pigmented BCC but not pigmented SCC.

Discussion
In 2009 di Giorgi et al reported a case on the upper lip of a 45-year-old woman [12]. Dermatoscopically there were no blue structures but there was a central red and brown structureless area with radial lines at the periphery in a circumferential distribution. In this case a dermatologist had previously made a diagnosis of seborrheic keratosis. After dermatoscopic assessment the authors made a provisional diagnosis of a "suspect melanocytic lesion." Also in 2009, Yoshida et al reported a 2.2 x 1.5 cm pigmented SCC on the nose of a 101-year-old Japanese woman [13]. They published dermatoscopic images which revealed a centrally ulcerated lesion with serpentine vessels and bordering the ulceration, a structureless pigmented area displaying predominantly blue color with some brown. Blue radial lines project focally at the periphery.
In the case we present here malignancy was predicted on the basis of the "chaos and clues" algorithm [17]: there was "chaos" (asymmetry) and the clues of "eccentric structureless zone (blue)" and "polymorphic vessels." Of the three pigmented malignancies (pigmented melanoma, pigmented BCC, and pigmented SCC), pigmented SCC should be considered because of the presence of surface scale (seen macroscopically) and white circles (seen dermatoscopically). The blue color was not consistent with pigmented SCC in-situ; the color blue indicated the presence of melanin in the deep dermis [18]. Therefore, invasive pigmented SCC was considered, and this was confirmed histopathologically.

Conclusion
Pigmented cutaneous invasive SCC is uncommon with few reports in the literature. Four out of five previously reported cases with dermatoscopy had a blue structureless zone. The case we report, like previous cases, had clues to malignancy and in this case these included asymmetry, a blue structureless zone and polymorphic vessels. The presence of surface scale and the presence of white circles may be clues to squamous cell carcinoma. The dermatoscopic finding of white circles as a clue to invasive squamous cell carcinoma needs to be confirmed with the study of more cases.