Rare epidermal panfolliculomas: a case series with clinical-pathologic correlation

Summary: Panfolliculoma is a rare, benign follicular neoplasm characterized histologically by a dermal cystic tumor with differentiation of follicular structures toward all parts of the hair follicle. Clinically, these lesions often appear as slow-growing nodules on the scalp and face in middle-aged adults, and they are frequently mistaken for an epidermal inclusion cyst, basal cell carcinoma, or squamous cell carcinoma. We present 2 cases of epidermal panfolliculoma with unusual presentation on the trunk and unique histologic findings. A 64-year-old man with a history of amelanotic melanoma and numerous non-melanoma skin cancers presented with a 6mm pink, shiny papule on the upper back, thought to clinically resemble a basal cell carcinoma. Shave biopsy revealed an epidermal panfolliculoma, a rare variant of panfolliculoma confined to the epidermis. A 62-year-old woman presented with a 5mm papule on the upper back thought to clinically represent an irritated seborrheic keratosis or a squamous cell carcinoma. Shave biopsy was consistent with an epidermal panfolliculoma. Histological diagnosis can be challenging as the dermatopathologist must be aware of the rare diagnosis and recognize the varied follicular differentiation. We will review the distinguishing clinical and histological features of epidermal panfolliculoma and the differential diagnosis including other follicular neoplasms.