Accuracy of partial biopsies in the management of cutaneous melanoma

The recommended method for histopathological diagnosis of cutaneous melanoma is excisional biopsy, although partial biopsies (shave and punch) are often used. Following a partial biopsy, treatment guidelines recommend a narrow excisional biopsy to plan definitive management. There is limited evidence on the benefits of direct wide local excision (WLE) following diagnostic partial biopsies.

Retrospective cohort study of cutaneous melanoma cases, from two tertiary referral centres from January 2013 to December 2015. Demographic and histopathological data, including tumour thickness (T-stage) from initial biopsy and subsequent excisions, were collected. Logistic regression was used to examine histopathological T-staging between biopsy and subsequent excisions (upstaging).

2304 melanomas (2157 patients) were identified; 455 shave, 308 punch, 14 incisional and 1527 excisional biopsies. Out of 1527, 5 (<1%) excisional biopsies were upstaged from original biopsy T-stage to final WLE; compared to 28/455 (6%) for shave, 45/308 (15%) for punch and 2/14 (14%) for incisional biopsies. Histopathology upstaging were increased with punch (OR, 52.1; 95% CI, 20.5-132.4. P < 0.001) and shave biopsy (OR, 20.0; 95% CI, 7.7-52.0. P < 0.001) compared to excisional biopsy. Upstaging rates of 9.4% for desmoplastic (OR, 6.9; 95% CI, 2.4-19.7. P < 0.001) and 21.9% for acral lentiginous (OR, 18.4; 95% CI, 6.9-49.2. P < 0.001) melanomas were elevated compared to 1.4% for superficial spreading melanoma.

In most cases, partial biopsy (particularly shave biopsy) can provide sufficient information to plan for definitive surgical melanoma management. Punch and incisional biopsies have elevated upstaging rates, a consideration in planning therapy. Partial biopsies of desmoplastic or acral lentiginous melanomas have high rates of upstaging and should have a complete excision prior to definitive treatment.