Abstract
Pigmented squamous cell carcinoma is a rare neoplasm arising mostly in mucous membranes or in sun-exposed skin. We describe a case of this tumor in a 70 year-old man who presented with a pigmented ulcerated nodule on his lower back. Microscopic examination revealed a squamous cell carcinoma (SCC) with atypical proliferation of cells with individual cell keratisation and keratin pearls’ formation. Apart from the squamous cell carcinoma a population of cytologically bland dendritic melanocytes was also present, a process that has been described as tumor cell colonization. Differential diagnosis of pigmented SCC includes melanoma with pseudoepitheliomatous hyperplasia, pigmented metatypical basal cell carcinoma and squamomelanocytic tumor, a recently described combined tumor. A small number of cases of pigmented SCC have been referred in the literature mainly located in mucosal surfaces such as the oral and nasal cavity and the conjunctiva but also in sun-exposed cutaneous sites especially at the skin of the head. In the present study, a case of pigmented SCC arising in sun protected skin is described. The authors review the published literature and discuss the histologic differential diagnosis of pigmented SCC as well as the possible mechanisms of melanocytes’ colonization in pigmented non-melanocytic malignant neoplasms.
Highlights
Squamous cell carcinoma (SCC) is the second most common cutaneous malignancy with basal cell carcinoma being the most frequent
A small number of cases of SCC which contain a population of non neoplastic melanocytes, called pigmented SCCs have been reported In the English literature [5,6]
The present report describes an unusual case of pigmented skin tumor that fulfills the criteria for its inclusion in the category of pigmented squamous cell carcinomas
Summary
Squamous cell carcinoma (SCC) is the second most common cutaneous malignancy with basal cell carcinoma being the most frequent. A small number of cases (less than 40) of SCC which contain a population of non neoplastic melanocytes, called pigmented SCCs have been reported In the English literature [5,6]. The neoplastic keratinocytes were admixed with a large number of cells containing melanin pigment (melanocytes or melanophages) (Figure 3).
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