Abstract
We report a case of exceedingly rare cutaneous neoplasm with histological features of malignancy and uncertain biological potential. The nodular, darkly pigmented facial tumor with central exulceration, size 12 x 10 x 7 mm, of the skin 61-year-old man preauricular left was completely exised. Histologically tumor consists of atypical squamous cells, which express signs of moderate to significant pleomorphism, mitotically active, with foci forming of parakeratotic horn cysts ("pearls"). Characteristically tumor also consists of large number of atypical melanocytes with multifocal pattern, inserted between atypical squamous cells, and which contain large amount of dark brown pigment melanin. Immunohistochemically, squamous cells stain positively with keratin (CK116), melanocytes were stained with S -100 protein, HMB 45, and vimentin, but failed to stain with CK 116. To our knowledge this is the sixth reported case in world literature. The follow-up time of four years no evidence of recurrence or metastasis, similar all reported cases, but it is too short period in estimation to guarantee a benign course. However, it appears that this group of neoplasm may have different prognosis from pure squamous carcinoma or malignant melanoma.
Highlights
Malignant melanoma and squamous cell carcinoma most commonly arise on background of exposure to sunlight in somewhat similar patient populations ( )
It is the only one with epidermal defect that more suggests ischemia due to the tumor growth that epidermal origin considering that the surrounding epidermis has regular features. These tumors show an intimate admixture of melanocytic and squamoid cells, in contrast to collision tumors in which there are distinctly separate components of melanocytic and epithelial cells ( ). Epithelial tumors such as squamous cell carcinoma have been reported to arise adjacent to malignant melanomas; the two cell populations were not intimately admixed (, )
Occasional malignant melanomas aberrantly express keratin (, ), but the pink plate-like cytoplasm and formation of squamous pearls by keratin-positive cells excludes the possibility that they represent melanocytes ( )
Summary
MIRSAD DORIĆ ET AL.: DERMAL SQUAMOMELANOCYTIC TUMOR: NEOPLASM OF UNCERTAIN BIOLOGICAL POTENTIAL Malignant melanoma and squamous cell carcinoma most commonly arise on background of exposure to sunlight in somewhat similar patient populations ( ). Has been described in the pathology literature neoplasm with features of both malignant melanoma and squamous cell carcinoma ( , ) and named dermal squamomelanocytic tumor.
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