Secondary ossification assoc. with seborrheic keratosis adja
The present case has been published in the Indian Journal of Dermatology.

An 80-year-old female reported, complaining of a facial tumor which had existed for last 8 years. She denied either prior local trauma or infection at the site. Physical examination showed a relatively well-circumscribed erythematous plaque with infiltration on the left cheek, and in addition, a brownish keratotic slightly-elevated nodule was located adjacently.

A biopsy specimen revealed well-circumscribed basaloid tumor nests in the upper to mid-dermis. The tumor cells were uniform in size with oval nuclei and scant cytoplasm with peripheral palisading, and the tumor nests were surrounded by myxomatous stroma, which was positively stained by alcian blue, suggestive of basal cell carcinoma.

A total resection including the adjacent keratotic tumor was performed. Histological features of the keratotic nodule showed reticular epidermal proliferation containing pseudocysts, extending to the upper dermis. Of note, a lamellar bony structure of homogeneous materials containing osteoblastic cells was found in the surrounding stroma.

The present case developed basal cell carcinoma and seborrheic keratosis in a close location, however, secondary ossification (osteoma) was observed just beneath the seborrheic keratosis, but not associated with basal cell carcinoma.

Benign skin tumors showing secondary ossification are most common in melanocytic nevus and pilomatricoma, whereas other benign tumors are rare, i.e., apocrine hidrocystoma, lipofibroma, neurofibroma, pyogenic granuloma, and keratoacanthoma.

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