Utility of Skin Biopsy and Culture in the Diagnosis and Classification of Chronic Ulcers: A Single-Institution, Retrospective Study

In the United States, chronic ulcers affect 6.5 million people, with a cost of ≈$20 million annually. The most common etiology of chronic ulcers in the United States is venous stasis, followed by arterial insufficiency and neuropathic ulcers. Less common causes of chronic ulcers include infection, inflammatory etiologies such as vasculitis and pyoderma gangrenosum, and neoplastic causes. Obtaining skin biopsy and tissue culture can be helpful in diagnosing unusual causes of chronic ulcers; however, there are little data on the diagnostic utility of skin biopsy in rendering a definitive diagnosis of the etiology of chronic ulcers. A retrospective study of all skin ulcers biopsied during a 10-year period at the University of Washington was undertaken. Re-excisions and surgical wounds were excluded. A total of 270 ulcer biopsy specimens were included. In 48% of cases, no specific diagnosis could be rendered histologically. 44.8% of chronic ulcers biopsied were due to atypical causes, with neoplasms (basal cell carcinoma, squamous cell carcinoma, melanoma, and cutaneous T-cell lymphoma) being the most common. Vasculitis and pyoderma gangrenosum each represented 1.5% of rendered diagnoses. Concomitant skin culture was performed in 28.9% of cases, and special stains [acid-fast bacilli, Brown and Brenn (B&B), Grocott's methenamine silver, and periodic acid-Schiff stains] were performed in 34.0%. Although more than half (49 of 78) of tissue cultures were positive, only 6.8% (12 of 175) of special stains on tissue sections were positive. We conclude that although the etiology of many ulcers cannot be determined by routine histology alone, skin biopsy of ulcers remains a critical part of the workup given that when a specific cause can be determined, atypical etiologies, including neoplasms, represent a significant proportion of chronic ulcers. Limitations of our study include referral bias. Our results also confirm the higher diagnostic yield of conventional tissue culture compared with special tissue stain biopsies of skin ulcers.