Skin biopsy — SAQ

Stem

A 54-year-old man presents to the dermatology clinic with a 7 mm pigmented lesion on his left calf that he first noticed 6 months ago. His partner reports it has been getting darker and more irregular over the past 3 months. On examination there is a 7 × 6 mm lesion with asymmetry, two notched borders, colour variegation (dark brown, black and red areas) and a small central crust. There is no palpable inguinal lymphadenopathy. Dermoscopy shows an atypical pigment network with irregular streaks, a blue-white veil and regression structures.

Questions

a) What is the most likely diagnosis, and what features make this lesion high-risk? (2 marks) [1]

Invasive cutaneous melanoma, almost certainly superficial spreading subtype. The patient meets multiple ABCDE criteria (asymmetry, border irregularity, colour variegation, diameter >6 mm, evolution over 3 months) and the dermoscopy adds three specific high-risk features: an atypical pigment network, irregular streaks, and a blue-white veil with regression. The lesion is on the calf of an adult male (a typical site for superficial spreading melanoma in fair-skinned populations), and the central crust and red areas suggest a possible amelanotic / hypomelanotic component, which is itself an independent predictor of thickness. The absence of palpable regional nodes does not exclude nodal metastasis (sentinel node biopsy detects microscopic deposits) and is not reassuring at this stage. [1]

b) What is the appropriate diagnostic biopsy, and what are the key technical details (site, orientation, depth, specimen handling)? (3 marks) [1]

The appropriate diagnostic procedure is full-thickness excisional biopsy with a narrow clinical margin of 2-3 mm, oriented along the resting skin tension lines of the calf (which run along the long axis of the limb). The incision is a 3:1 to 4:1 ellipse, performed under local anaesthetic (1% lidocaine with adrenaline 1:100 000). The depth must extend into subcutaneous fat (a shave biopsy is absolutely contraindicated because it transects the lesion horizontally and the deepest tumour cell — the basis of the Breslow thickness — is left behind; AJCC T-staging, sentinel node biopsy threshold and definitive wide local excision margins all depend on the Breslow thickness). [1]

The specimen is inked at multiple margins (or sutures are placed as orientation markers) and is submitted in 10% neutral buffered formalin at a 10:1 formalin-to-tissue ratio with the clinical information and the precise anatomical site on the requisition. If the lesion is too large or anatomically awkward to excise in primary care (the lesion here is technically straightforward and excisional biopsy by the dermatologist is the rule), the patient is referred urgently for definitive surgical management. [1]

c) What definitive treatment follows the diagnostic biopsy, and how is it determined? (3 marks) [1]

The definitive treatment is determined by the Breslow thickness reported on the excisional biopsy. Wide local excision (WLE) with Breslow-derived clinical margins is then performed (typically within 2 to 4 weeks of the diagnostic biopsy): 1 cm margin for melanoma in situ or Breslow ≤1 mm; 1 to 2 cm margin for Breslow 1.01 to 2 mm; 2 cm margin for Breslow >2 mm. Sentinel lymph node biopsy (SLNB) is discussed and offered for melanomas with Breslow thickness ≥0.8 mm (with ulceration) or ≥1 mm (without ulceration), or for thinner melanomas with high-risk features (ulceration, high mitotic rate), per NCCN / AJCC guidance. [1]

Following definitive surgery, the patient is staged with the AJCC 8th edition TNM system (T by Breslow, N by SLNB or clinical examination, M by imaging) and is offered adjuvant systemic therapy (immunotherapy with pembrolizumab or nivolumab for stage III; targeted therapy with dabrafenib plus trametinib for BRAF V600E-positive stage III) if indicated. [1]

d) What are the key complications of excisional biopsy, and what determines the cosmetic outcome? (2 marks) [1]

Immediate complications include bleeding (usually controlled by pressure, electrocautery and figure-of-eight suture), infection (under 2% on the calf), and local anaesthetic toxicity (which is prevented by keeping the lidocaine dose under 7 mg/kg with adrenaline, or 4 mg/kg plain). Early complications include haematoma, dehiscence (from premature activity, infection or suture removal too early), and suture granuloma. Late complications include hypertrophic or keloid scar (higher on the chest, ear, deltoid, and in Fitzpatrick IV-VI), post-inflammatory hyperpigmentation (usually temporary, peaking at 3-6 months), and hypopigmentation (often permanent, more cosmetically limiting). [1]

The cosmetic outcome is determined primarily by orientation of the ellipse along the resting skin tension lines (along the long axis of the calf in this case), by length:width of 3:1 to 4:1 to allow primary closure without dog-ears, by layered closure (deep dermal buried absorbable sutures offloading tension from the epidermis, then fine epidermal non-absorbable sutures), and by suture removal at 7-14 days depending on site, with photoprotection of the scar for 12 months. [1]

---

References

1. [1]Greenwood JD, Merry SP, Boswell CL. Skin Biopsy Techniques Prim Care, 2022.PMID 35125151
2. [2]Pickett H. Shave and punch biopsy for skin lesions Am Fam Physician, 2011.PMID 22046939
3. [3]Ng JC, Swain S, Dowling JP, et al. The impact of partial biopsy on histopathologic diagnosis of cutaneous melanoma: experience of an Australian tertiary referral service Arch Dermatol, 2010.PMID 20231492
4. [4]Kim TH, Shin K, Kim YS, et al. Effect of changes in Breslow thickness between the initial punch biopsy results and final pathology reports in acral lentiginous melanoma patients Sci Rep, 2021.PMID 34615974
5. [5]Jones S, Ho J, Fine J, et al. Clinical Impact and Accuracy of Shave Biopsy for Initial Diagnosis of Cutaneous Melanoma J Surg Res, 2023.PMID 36739830
6. [6]Kumudhini S, Pai R, Shetty A. A comparative study of Michel's medium versus honey as a transport medium for skin specimens prior to direct immunofluorescence microscopy and antigen mapping J Cutan Pathol, 2019.PMID 31087406
7. [7]Meijer JM, Aries JCQ, Diercks GFH, et al. Serration pattern analysis for differentiating epidermolysis bullosa acquisita from other pemphigoid diseases J Am Acad Dermatol, 2018.PMID 29154993
8. [8]Rose C, Bröcker EB, Leverkus M. Histopathology of panniculitis--aspects of biopsy techniques and difficulties in diagnosis J Dtsch Dermatol Ges, 2012.PMID 22084866
9. [9]Streicher JL, Zullo SW, Hinds BR, et al. Cutaneous manifestation of α₁-antitrypsin deficiency: panniculitis absent on biopsy Cutis, 2014.PMID 24999642
10. [10]Knopp EA, Bhatt M, Elston D. Updates in the Interpretation of Alopecia Biopsies Dermatol Clin, 2026.PMID 41951327
11. [11]Rutnin S, Somanachan I, Thanomkitti K, et al. Variation of Hair Follicle Counts among Different Scalp Areas: A Quantitative Histopathological Study Skin Appendage Disord, 2022.PMID 35118125
12. [12]Rahman SM, Yoneyama K, Hasan R, et al. Basal cell carcinoma has greater subclinical extension than squamous cell carcinoma: a cohort study Arch Dermatol Res, 2024.PMID 38761227
13. [13]Greywal T, Adamson AS, Bichakjian CK, et al. Key characteristics of basal cell carcinoma with large subclinical extension J Eur Acad Dermatol Venereol, 2020.PMID 31419354
14. [14]Arp AS, Le BR, Prabhu N. The Anesthetic Effects of Lidocaine with Epinephrine in Digital Nerve Blocks: A Systematic Review J Am Podiatr Med Assoc, 2023.PMID 37713411
15. [15]Hong IS, Heiner LR. Epinephrine-Containing Digital Nerve Block: A Case of Digital Tip Necrosis Leading to Amputation in a Patient With No Known Vascular, Rheumatologic, or Smoking History J Hand Surg Glob Online, 2021.PMID 35415561
16. [16]Mullen JT, Feng L, Xing Y, et al. Dermatofibrosarcoma Protuberans: Wide Local Excision Versus Mohs Micrographic Surgery Surg Oncol Clin N Am, 2016.PMID 27591501
17. [17]Elshot YS, Ottevanger RR, Bekkenk MW, et al. Lentigo maligna (melanoma): A systematic review and meta-analysis on surgical techniques and presurgical mapping by reflectance confocal microscopy J Eur Acad Dermatol Venereol, 2023.PMID 36652277
18. [18]Noble CA. Clinical-pathologic correlation: The impact of grossing at the bedside Semin Diagn Pathol, 2025.PMID 38336505