Squamous cell carcinoma in-situ arising in hypertrophic actinic keratosis with associated cutaneous horn?

Diagnosis: Squamous cell carcinoma in situ (SCCIS) arising in hypertrophic actinic keratosis with associated cutaneous horn.

Clinical presentation: A 70-year-old male with a history of significant sun exposure presents with a 2 cm, asymptomatic, flesh-colored papule with a central horn on his left cheek. The lesion has been present for several months and has been slowly enlarging.

Dermoscopy: Dermoscopy reveals a well-demarcated, erythematous patch with a central, hyperkeratotic plug. The surrounding skin exhibits actinic damage, including telangiectasias, solar elastosis, and multiple actinic keratoses.

Histopathology: A biopsy of the lesion shows features consistent with SCCIS arising in hypertrophic actinic keratosis. The epidermis shows marked hyperplasia and atypia, with loss of normal rete ridges and dysplastic keratinocytes. There is full-thickness epidermal involvement, but the basement membrane is intact. The overlying stratum corneum is thickened and shows hyperkeratosis. In addition, there is a cutaneous horn, which is a projection of the stratum corneum filled with keratin.

Differential diagnosis: The differential diagnosis for this lesion includes other forms of non-melanoma skin cancer, such as basal cell carcinoma, as well as benign lesions such as seborrheic keratosis. A biopsy is necessary to confirm the diagnosis of SCCIS.

Treatment: Treatment options for SCCIS arising in hypertrophic actinic keratosis include surgical excision, topical chemotherapy, and radiation therapy. The choice of treatment will depend on the size and location of the lesion, as well as the patient's overall health and preferences.

Prognosis: The prognosis for SCCIS arising in hypertrophic actinic keratosis is generally good, with a low risk of metastasis. However, early diagnosis and treatment are important to prevent the development of invasive squamous cell carcinoma, which can be more difficult to treat.