Skin Malignancy in the Military: A Number Needed to Biopsy Analysis

Skin malignancy has increased in prevalence over the last 15 years and effective diagnosis is required for adequate treatment. Retrospective data analysis of skin biopsy data has shown correlation between various independent variables, but no studies have been shown to directly assess skin malignancy risks for military personnel. Assessing correlation could lead to more effective, targeted screening programs that could lead to decreased mortality from skin malignancies. We present a 1-year analysis of the number needed to biopsy (NNB) to detect skin cancer and analysis of military-specific risk factors in a military dermatology training program. The present study aims to (1) compare skin biopsy yields to civilian institutions and patient populations and (2) determine significance of exposure variables including age, gender, military beneficiary status, branch of service, and military rank.

We performed a retrospective observational study over 1 year by identifying all skin biopsies performed in the Walter Reed National Military Medical Center dermatology clinic from August 2015 to July 2016. Utilizing the pathology reports, we manually excluded biopsies performed for the purpose of ruling out inflammatory/immunologic conditions or cosmeses and focused only on encounters performed to rule out basal cell carcinoma, squamous cell carcinoma, or melanoma. We decided to exclude malignant diagnoses that were exceedingly rare or could mimic inflammatory conditions, such as cutaneous T-cell lymphoma. For uncertain diagnoses with vague context per pathology report, previous office clinic notes and pre-biopsy differential were referenced and included only if melanoma or non-melanoma skin cancer (NMSC) diagnosis was the intended indication.

A total of 3,098 biopsies were included in the study, diagnostic for 1,084 total skin malignancy and 54 melanoma diagnoses. Melanoma comprised 4.98% of all skin malignancy diagnosed. The NNB for all skin malignancy was 2.86 (95% CI 2.76-2.96) and NNB for melanoma and NMSC was 20.93 (95% CI 19.70-22.15) and 1.91 (95% CI 1.83-2.00), respectively. Patient age, gender, and military rank significantly impacted NNB values (P < .001).

The proportion of melanoma skin cancers is notably increased in our population compared to published population statistics with comparable total biopsy yields. Skin biopsy for purpose of screening for malignancy should be performed in the military population and consideration should be made for gender, age, and rank. Our findings can further expand on military risk factors for skin cancer and aid in further multivariant modeling.