A 28-year-old previously healthy woman comes to the office for evaluation of a raised, pigmented skin lesion on her leg. The patient has had no itching or pain and cannot remember how long she has had the lesion. She has used tanning machines a few times in the past but denies excessive sun exposure. She is particularly concerned about the risk of malignancy as her father was recently diagnosed with skin cancer. Skin examination shows the nodule seen in the image below. A biopsy of the lesion reveals nests of uniform round cells at the basal portion of the epidermis that extend into the underlying dermis. The cells contain inconspicuous nucleoli and show no mitotic activity. Which of the following is the most likely diagnosis?

Question

A 28-year-old previously healthy woman comes to the office for evaluation of a raised, pigmented skin lesion on her leg.  The patient has had no itching or pain and cannot remember how long she has had the lesion.  She has used tanning machines a few times in the past but denies excessive sun exposure.  She is particularly concerned about the risk of malignancy as her father was recently diagnosed with skin cancer.  Skin examination shows the nodule seen in the image below.  A biopsy of the lesion reveals nests of uniform round cells at the basal portion of the epidermis that extend into the underlying dermis.  The cells contain inconspicuous nucleoli and show no mitotic activity.  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

11ec160b_38fd_c882_9249_e7df9f9627f1_MD0001_00 Melanocytic nevi are benign neoplasms composed of round, uniform melanocytes (nevus cells) that are mitotically quiescent. They are typically <6 mm in diameter, and have a regular outline with a symmetrical, sharply demarcated border and a homogenous surface. Melanocytic nevi are progressive lesions that typically mature through the following phases: Junctional nevi are characterized by aggregates of nevus cells limited to the dermoepidermal junction (Choice C). They typically appear as flat, black- to brown-pigmented macules with darker coloration in the center than the periphery and preserved skin markings. Compound nevi form as the aggregates of nevus cells extend into the dermis. Compound nevi are raised papules with uniform brown to tan pigmentation. This patient's lesion is a compound nevus as it has both dermal and epidermal involvement. Intradermal nevi are considered to be older lesions in which the epidermal nests of nevus cells have been lost. The remaining dermal nevus cells lose tyrosinase activity and produce little to no pigment. Intradermal nevi are skin- to tan-colored, dome-shaped, and sometimes pedunculated. (Choices A and D) Malignant melanoma is characterized by irregular and asymmetrical borders with variable coloration, diameter >5 mm, and evolution over time. Melanomas typically expand superficially at first but may extend vertically into the dermis and subcutaneous tissues, portending a poor prognosis. Compared to nevus cells, melanoma cells are larger, contain larger nuclei with prominent nucleoli, and have greater mitotic activity. Atypical (dysplastic) nevi can resemble melanoma but typically have less extreme features. The melanocytes commonly show cellular atypia and form coalescing nests that may fuse into a continuous layer at the dermoepidermal border. (Choice E) Pigmented basal cell carcinoma can present as papules, nodules, or plaques with rolled borders on sun-exposed areas. They can have varying degrees of pigmentation due to functional melanocytes within the lesion. The tumor cells resemble basal epidermal cells but extend into the dermis and form clusters with a palisade arrangement of peripheral cells. (Choice F) Seborrheic keratosis forms a hyperpigmented lesion with well-circumscribed borders, a dull surface, and a "stuck-on" appearance. On microscopic examination, the lesions are composed of small cells resembling basal cells, with variable pigmentation, hyperkeratosis, and keratin-containing cysts. Educational objective: Compound nevi are benign proliferations of melanocytes that involve both the dermis and epidermis. The lesions appear as slightly raised papules with uniform pigmentation and symmetrical sharp borders. __________ References: Optimal management of common acquired melanocytic nevi (moles): current perspectives. (http://www.ncbi.nlm.nih.gov/pubmed/24672253)

A 28-Year-Old Previously Healthy Woman Comes to the Office for Evaluation