Merkel cell carcinoma (MCC), produced by MCV (Merkel cell polyomavirus) is known as a rare skin tumor
which can have an aggressive clinical evolution with an unfavorable prognosis.
Malignant nodular hidradenoma (MNH), first described as clear cell eccrine carcinoma by Keasbey and Hadley in 1954 (1-3) is an uncommon, highly malignant, primary skin tumor
derived from eccrine sweat glands (1-6) accounting for approximately 6% of malignant eccrine tumors.
In this 2002 study the mouse skin tumor
model, sesamol was found to provide a 50% reduction in skin papillomas at 20 weeks after promotion with 12-O-tetradecanoylphorbol 13-acetate.
in 1997  and since then, less than 60 cases have been reported in the literature, making it an uncommon skin tumor
that may pose diagnostic challenges to clinicians and pathologists.
Pilomatrixoma is a rare benign skin tumor
arising from hair follicle stem cells which is also known as calcifying epithelioma of Malharbe.
In cases where distinction between metastatic and primary skin tumor
is difficult, a variety of immunohistochemical staining panels can be helpful [13-17].
Malignant melanoma (MM) was the most common malignant skin tumor
encountered in this study, constituting 61 cases (33%).
Thus, topical application of sulforaphane-containing broccoli sprout extracts is a promising strategy for protecting against skin tumor
formation after exposure to UV radiation.
The formation of skin tumors
in these mice depended on polyamine biosynthesis, especially PU, because treatment with the specific inhibitor of ODC activity, alpha-difluoromethylornithine, blocked skin tumor
formation and caused rapid regression of existing tumors (12).
Chondroid syringoma is a rare, generally benign skin tumor
arising from sweat glands and often located in the head and neck region.
"Hundreds of thousands of patients may be unnecessarily burdened with the belief that they have had a potentially lethal cancer (melanoma) when in fact they have had a skin tumor
that is very unlikely to be lethal," he wrote.
I remember a slide of a large bovine papilloma [a benign skin tumor
in cattle] shown by a veterinarian.