The patient presented with hutchinson’s sign, longitudinal melanonychia and no swollen lymphnodes. He had no first-degree relatives with melanoma, no prior history of melanoma (invasive or in situ) and no prior history of other skin cancers.

Background on Subungual Melanoma (SM)
SM is a rare but serious malignancy arising from the nail matrix. Early diagnosis is crucial for treatment and prognosis. Nail changes are often benign; however, malignancy must always be considered in cases of pigmented nail lesions, particularly longitudinal brown or black streaks (longitudinal melanonychia). Biopsy is required when diagnostic uncertainty persists after clinical and dermoscopic evaluation.

The incidence of SM is not directly associated with ethnicity in terms of increased risk; however, SM accounts for up to 33% of all melanoma cases in individuals with darker skin tones, including African, Latin American, and Asian populations. This reflects the overall lower incidence of cutaneous melanoma in these groups. In Western countries, SM represents approximately 0.7–3.5% of all melanomas.
The highest incidence occurs between 50 and 70 years of age, with equal distribution between men and women. The etiology is often unknown, as ultraviolet radiation is implicated in only approximately 10% of cases.
SM typically originates in the nail matrix and subsequently spreads to the nail plate, presenting as longitudinal melanonychia (LM). Hutchinson’s sign may be observed in more advanced stages, characterized by brown or black pigmentation extending into the periungual skin, which is particularly suggestive of this melanoma subtype. Nail splitting or bleeding from the nail bed may also occur.

Indications for biopsy
• Pigmented longitudinal lesion in the direction of nail growth (melanonychia) with atypical features
• Hutchinson’s sign (pigment lesion in the periungual skin)
• Rapidly growing pigmented nail lesion or nevus
• Suspicion of malignancy following dermoscopic evaluation
• Insufficient diagnostic certainty using non-invasive methods

Differential Diagnoses
Benign conditions:
• Subungual hematoma (trauma-related)
• Onychomycosis (fungal infection)
• Melanocytic hyperplasia (brown, pigmented spots or bands)
• Pyogenic granuloma
• Glomus tumor
• Subungual exostosis
• Myxoid pseudocyst
Malignant conditions:
• Subungual melanoma
• Squamous cell carcinoma (SCC)

ABCDEF Rule for Subungual Melanoma
A – Age: 40–70 years
B – Band: Longitudinal melanonychia > 3 mm; brown/black, broad band with irregular borders
C – Change: Change in size or growth pattern
D – Digit involvement: Most commonly dominant thumb, followed by nondominant thumb, index finger, or great toe; single digit involvement more common than multiple
E – Extension: Extension of pigment into the nail fold (Hutchinson’s sign); ethnicity
F – Family history: Family history or personal history of melanoma

Patient Evaluation
• Document the appearance and width of the pigmented band and the presence or absence of Hutchinson’s sign.
• Perform dermoscopy to evaluate the pigment pattern and exclude benign causes.
otUse ultrasound gel rather than alcohol under the dermatoscope.
• Record relevant history, including trauma, dermatologic conditions, or family history.
• Inform the patient about the risk of nail dystrophy and possible permanent nail loss.
• Ask for local anesthesia without epinephrine.
• Ensure hemostasis using a tourniquet.
• Select the biopsy site at the proximal origin of the pigmentation within the nail fold.
• Consider suturing defects > 3 mm to optimize cosmetic outcome.

Anatomy
The nail unit consists of:
•tNail matrix: Growth zone of the nail plate.
•tNail bed: Underlying tissue securing the nail plate to the finger.
•tNail plate: Keratinized structure forming the visible part of the nail.
•tNail folds (cuticle/eponychium): Surrounds the nail plate and protect against infection.

•tPreoperative skin antisepsis.
•tSterile draping (consider a surgical fenestrated drape).
•tPerform a digital nerve block at the base of the affected finger or. toe.

•tPrepare the tourniquet by cutting into the finger of a surgical glove proximally and distally.

•tApply a proximal tourniquet

•tConfirm adequate anesthesia.
•tIncise the nail fold on both sides of the pigmentation.

•tUndermine the nail fold to visualize the pigmented tissue using first a scalpel and then dissection scissiors.

•tA punch biopsy (preferably 3–4 mm) can be performed with or without removal of the nail plate. If the punch biopsy is performed without nail plate removal, then it is performed as shown below. Press down to the periosteum at the origin of pigmentation.
•tSubmit the nail plate, biopsy specimen, and any intervening tissue separately in separate pathology specimen containers and send to pathology.
•tAchieve hemostasis.

•tGrasp the free edge of the nail plate with a hemostat and avulse the nail plate with a twisting motion.
•tIf difficult to detach, perform blunt dissection using a curved dissection scissor beneath the nail plate along the nail groove.
•tSubmit the nail plate, biopsy specimen, and any intervening tissue separately to pathology.

•tWhen the nail plate is removed, a punch biopsy (preferably 3–4 mm) can be performed down to the periosteum at the origin of pigmentation.

•tAchieve hemostasis.

•tTrim a syringe barrel (typically 10 mL for fingers and toes 2–4; 20 mL for the great toe) to match the size of the nail bed, ensuring smooth, rounded edges.

•tCreate two holes at the proximal end using a needle.

•tSecure the customized nail splint to the nail fold using 4-0 Nylon sutures through the two holes.

•tSuture the incisions to nail fold with 4-0 Nylon sutures.

•tApply sterile dressing. For instance, a protective finger dressing or a gauze secured with micropore tape over the nail bed.

• Use ultrasound gel rather than alcohol under the dermatoscope.
• Apply a digital tourniquet to create a bloodless field, improving visualization of tissue structures and providing crucial hemostasis.

• Submit the nail plate, biopsy specimen, and any intervening tissue separately to pathology.
• Consider if nail removal is indicated, or if telescopic biopsy is preferable.

• Keep the area clean and dry.
• Apply sterile dressing and change as needed.
• Remove sutures and the temporary nail substitute after 14 days.
• Provide instructions regarding signs of infection and bleeding.
• Communicate histopathological results when available.

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