Evaluation of a Long-Standing Pigmented Lesion on the Plantar Foot of an Adolescent

Case at a Glance

A healthy 15-year-old male presented for evaluation of a small, dark, asymptomatic spot on the sole of his foot. The lesion was recently noticed by his mother but had reportedly been present and unchanged for several years. The consultation was prompted by a family history of skin cancer.

Patient's Story

The patient is a 15-year-old, 6'0", 190 lb adolescent male in excellent health, with no known medical conditions or current medications. His mother brought him for evaluation after she noticed a small, black spot on the sole of his foot. Upon questioning, the patient stated that the spot had been there for "years" and had not caused any pain, itching, or bleeding. Despite the lesion's long-standing and stable nature, the family's history of skin cancer raised concern, prompting them to seek medical advice.

Initial Assessment

On physical examination, the patient was a well-developed, healthy-appearing adolescent. Examination of the plantar aspect of the foot revealed a single, well-demarcated, dark brown to black macule. It was approximately 3-4 mm in diameter, round in shape, with regular borders and homogenous coloration. There were no signs of inflammation, ulceration, or nodularity. The lesion was non-tender to palpation. The remainder of the skin examination was unremarkable.

The Diagnostic Journey

The primary diagnostic challenge was to differentiate a benign melanocytic nevus from a malignant lesion, particularly acral lentiginous melanoma, which can occur on the soles of the feet. The patient's young age and the long history of a stable, unchanging lesion were strong indicators of a benign process. However, the acral location and the positive family history of skin cancer were considered risk factors that warranted a thorough evaluation. The differential diagnosis included a benign acral nevus, talon noir (black heel, a traumatic hemorrhage), and, less likely, acral lentiginous melanoma. The "ABCDE" criteria (Asymmetry, Border irregularity, Color variation, Diameter >6mm, Evolving) were applied; the lesion did not exhibit any of these suspicious features. The decision was made to refer the patient for a specialist dermatology consultation for dermoscopic evaluation.

Final Diagnosis

Presumptive diagnosis of Benign Acral Nevus.

Treatment Plan

The recommended plan was a referral to a dermatologist for definitive evaluation. The dermatologist would perform a dermoscopy to examine the lesion's pattern more closely. Based on these findings, the plan would either be reassurance and periodic monitoring (e.g., annual skin checks, baseline clinical photography) or an excisional biopsy if any atypical features were identified dermoscopically.

Outcome and Follow-up

The patient was scheduled for a dermatology appointment. The family was educated on the importance of regular self-skin examinations and instructed to seek immediate re-evaluation if they observed any changes in the lesion's size, shape, or color, or if it became symptomatic (e.g., itchy, painful, or started to bleed). The long-term plan involves routine monitoring to ensure the lesion remains stable over time.