Shave Biopsy for Autoimmune Bullous Diseases

By MIchael Krathen MD

“This simple, suture-sparing technique uses one biopsy to generate perilesional skin for DIF as well as an intact vesicle for H&E suitable to identify the histologic location of the split:  intra- versus subepidermal.” – Dr. Michael Krathen

Evaluating a skin biopsy by hematoxylin and eosin (H&E) staining as well as direct immunoflourence (DIF) has long been the gold standard in the diagnosis of autoimmune blistering diseases, including bullous pemphigoid (BP).

The punch biopsy technique is sometimes taught as the best method for skin sampling during assessment of possible autoimmune blistering disease cases, one biopsy aimed at the junction of the blister (H&E) and the other at a peri-lesional location (DIF).  However, shearing forces created by the punch technique can cause the blister roof to detach from the subjacent dermis after partial sampling of the blister wall.  While the loss of the bullous architecture on H&E does not preclude reaching the correct diagnosis, evaluation of the split level in the context of an intact blister with adjacent skin is best to rule out an intra-epidermal process.

Although known to many practitioners, shave biopsy to assess for the location of the split in a putatitive blistering disorder is, in our experience, not  always routinely performed as we still receive punch biopsy specimens for DIF analysis in this clinical setting.  Besides shearing off the blister roof, biopsy via punch methodology often requires the placement and subsequent removal of sutures during a repeat office visit.  Both to highlight the utility and remind the dermatology community of biopsying via shave methodology for this purpose, we present a case of bullous pemphigoid diagnosed in this manner.

A 98 year-old male presented with two intact tense bullae in the setting of severe generalized pruritus.  As this shave biopsy technique necessitates sampling of an entire blister, a bulla suitable in size (< 1 cm) for complete removal should be selected to facilitate wound healing.  Infiltration with 1% lidocaine with epinephrine into the mid and superficial dermis is followed by a thin shave biopsy via flexible dermablade.

The level of the biopsy should be deep enough to maintain the integrity of the blister and allow for assessment of the papillary and superficial reticular dermis yet shallow enough to allow for adequate secondary-intention healing.  The shave biopsy starts approximately 1 to 2 mm into adjacent normal skin and continues under the intact blister and extends 3 to 4 mm beyond the blister.  The extra 1-2 mm of skin obtained at the far side of the biopsy is then immediately removed via sharp scalpel dissection (Figure 1) and placed rapidly and directly into appropriate medium for DIF (such as Michel’s transport medium) to prevent specimen desiccation.  The intact blister with a small margin of surrounding uninvolved skin is then placed in formalin and sent for H&E.

Figure 1

Scalpel excises approximately 2 mm of perilesional skin immediately adjacent to a vesicle (arrowheads demonstrate vesicle margin).  The vesicle remains intact after specimen removal, as seen from the blister undersurface (inset).

Given standard processing by the pathology lab to ensure the skin surface is perpendicular to the mold bottom (i.e., bisecting the specimen and embedding on the edge with the cut surface down in the tissue cassette), all generated tissue sections should provide longitudinal en face views of the vesicle with adjacent normal skin on either side (Figure 2).  In this case, histology showed a subepidermal blister with numerous eosinophils (Figure 2, inset) and DIF showed linear deposition of IgG and C3 — consistent with the clinical suspicion of bullous pemphigoid.

Figure 2

Intact vesicle with subepidermal split, uninvolved perilesional skin at both vesicle margins (arrows), and subjacent papillary dermis throughout the length of the vesicle.  High power demonstrates the subepidermal split with numerous eosinophils (inset).

In summary, this simple, suture-sparing technique uses one biopsy to generate perilesional skin for DIF as well as an intact vesicle for H&E suitable to identify the histologic location of the split:  intra- versus subepidermal.

ABBREVIATION LIST
B: bullous pemphigoid
H&E: hematoxylin and eosin
DIF: direct immunoflourescence

About the author

MIchael Krathen MD

Michael Krathen, MD Department of Dermatology, Boston University, Boston Massachusetts Michael Krathen, MD is a third-year dermatology resident in the combined Boston University/Tufts University Residency program. He received both his undergraduate and medical degrees from the University of Pennsylvania. Dr. Krathen's professional interests include complex medical dermatology and cutaneous oncology.

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