An 80-year-old woman comes to the office for evaluation of a skin lesion. She has a black nodule on her back that has been present "for quite a while." The nodule has occasional associated itching, but no pain, bleeding, or recent change in appearance. Medical history is notable for hypertension, hypothyroidism, and mild dementia. The patient lives in an assisted living facility and does not use tobacco or alcohol. On examination, there is a raised nodule with a rubbery texture and oily surface, as shown in the image below. What is the most likely diagnosis?

Question

An 80-year-old woman comes to the office for evaluation of a skin lesion.  She has a black nodule on her back that has been present "for quite a while."  The nodule has occasional associated itching, but no pain, bleeding, or recent change in appearance.  Medical history is notable for hypertension, hypothyroidism, and mild dementia.  The patient lives in an assisted living facility and does not use tobacco or alcohol.  On examination, there is a raised nodule with a rubbery texture and oily surface, as shown in the image below.  What is the most likely diagnosis?

Quizplus · Accepted Answer

Seborrheic keratosis (SK [plural, keratoses]) is a common epidermal tumor seen in middle-aged or elderly individuals. SKs may be found almost anywhere on the body except the palms and soles. They can vary in appearance from nearly flat macules to raised, wart-like lesions, and can be pink/white, brown, or black. They have a velvety or greasy surface and well-demarcated border and are often described as having a "stuck-on" appearance. SKs are usually asymptomatic but occasionally can be pruritic or tender. They are benign lesions, although sudden onset of multiple SKs may indicate an occult internal malignancy (Leser-Trélat sign). macules The diagnosis of SK is based on the characteristic presentation. Biopsy is not usually necessary but will show small cells resembling basal cells, with variable pigmentation, hyperkeratosis, and keratin-containing cysts. Simple observation is the preferred management, but bothersome lesions may be treated with excision, cryosurgery, or electrodessication. keratin-containing cysts (Choice A) An acrochordon (skin tag) is a flesh-colored papule usually seen in regions of the body subjected to friction, such as the neck, axillae, and inner thighs. acrochordon (Choice B) Actinic keratosis is a pre-malignant lesion characterized by dry, scaly, flat papules with an erythematous base, seen most commonly in sun-exposed areas. Actinic keratosis (Choice C) The most common presentation of basal cell carcinoma is a slow-growing papule or nodule with a pearly, rolled border and overlying telangiectasias. Ulceration is common, as is bleeding following minor trauma. basal cell carcinoma (Choice D) Cutaneous warts are most common in children and young adults, and are usually seen on the hands, elbows, and feet. They are not usually pigmented. Cutaneous warts (Choice E) Biopsy is occasionally required to differentiate melanoma from SK. However, melanoma can usually be distinguished by its indistinct or irregular border, smooth or nodular surface, changing appearance over time, and predilection for sun-exposed areas. This lesion is located on the patient's back, has a rubbery texture, and has not recently changed in appearance. melanoma Educational objective: Seborrheic keratosis is a benign epidermal tumor that presents in middle-aged or elderly individuals as a tan or brown, round lesion with a well-demarcated border and "stuck-on" appearance. Diagnosis is based primarily on clinical appearance, and treatment is usually not required. References: Seborrheic keratosis. (http://www.ncbi.nlm.nih.gov/pubmed/18801147)

An 80-Year-Old Woman Comes to the Office for Evaluation of a Skin