J Cutan Pathol 2015: 42: 722–729 © 2015 John Wiley & Sons A/S. doi: 10.1111/cup.12504 Published by John Wiley & Sons Ltd John Wiley & Sons. Printed in Singapore Journal of Cutaneous Pathology Specificity of dermal mucin in the diagnosis of lupus erythematosus: comparison with other dermatitides and normal skin† Increased dermal mucin is a feature of lupus erythematosus (LE); Jeremy G. Vincent1 and however, its amount and distribution have not been well May P. Chan1,2 characterized. The differentiation of LE from other forms of 1 dermatitis can be challenging when other features of LE are Department of Pathology, University of Michigan, Ann Arbor, MI, USA and subtle or equivocal. One hundred and thirty-five skin specimens 2Department of Dermatology, University of showing LE, graft vs. host disease, erythema multiforme/fixed Michigan, Ann Arbor, MI, USA drug eruption, lichen planus, polymorphous light eruption †Presented in part at the 103rd Annual Meeting of (PMLE), urticaria, eczematous dermatitis and psoriasis and the United States and Canadian Academy of normal skin with and without photodamage were collected. The Pathology, San Diego, CA, on March 4, 2014. amounts of mucin in the papillary, superficial reticular and deep reticular dermis were scored from 0 to 3 on hematoxylin–eosin (H&E) and alcian blue (AB) stains, and compared between groups. The mean scores in the reticular dermis were significantly higher in LE than in other categories except PMLE and eczematous dermatitis. A combined H&E + AB score of ≥5 in the superficial reticular dermis gave an overall specificity of 85.7%for LE. Mucin in the papillary dermis failed to distinguish among entities. Normal photodamaged skin showed significantly more mucin in the superficial reticular dermis compared to non-photodamaged skin. While LE is associated with increased mucin deposition, scant to moderate amount of mucin alone has limited specificity and is common in other dermatitides or photodamaged skin. Keywords: lupus erythematosus, mucin, photodamage, May P. Chan, MD, polymorphous light eruption, tumid Department of Pathology, University of Michigan, 1301 Catherine Street, Medical Science I, Vincent JG, Chan MP. Specificity of dermal mucin in the M3261, Ann Arbor, MI 48109-5602, USA diagnosis of lupus erythematosus: comparison with other Tel: +1 734 764 4460, Fax: +1 734 764 4690, dermatitides and normal skin. e-mail: [email protected] J Cutan Pathol 2015; 42: 722–729. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd Accepted for publication March 15, 2015 Increased dermal mucin is one of the clas- moderate amount of dermal mucin is present, sic features of cutaneous lupus erythematosus but other classic features of LE are subtle or (LE); however, the amount and the distribu- equivocal. tion of mucin have not been well characterized. Increased dermal mucin and superficial to Differentiation of LE from other inflammatory deep perivascular and periadnexal lymphocytic dermatitides can be challenging when scant to infiltrate are fairly constant histopathologic 722 Specificity of dermal mucin features of cutaneous LE.1,2 Additional findings Both hematoxylin–eosin (H&E)- and alcian such as interface dermatitis, basement mem- blue (AB)-stained sections were evaluated for brane thickening and follicular plugging are dermal mucin in three different compartments: seen at varying frequencies depending on the papillary dermis, superficial reticular dermis and specific variant and chronicity of cutaneous deep reticular dermis. The amount of mucin LE.3–6 While the diagnosis of LE is straight- in each compartment was scored separately on forward when all of the above histopathologic H&E and AB as follows: 0, absent; 1 , scant wisps features are present in conjunction with clas- of mucin that are barely noticeable; 2, moder- sic clinical presentation, diagnostic difficulty ate amount of mucin almost filling the spaces arises when clinical information is limited and between collagen fibers; or 3, abundant mucin when only few classic features are observed pools filling and expanding the spaces between histopathologically. For example, other inter- collagen fibers. The H&E and AB scores in face or perivascular dermatitides may present each compartment were then combined to give with variable amount of dermal mucin and thus a total score of 0–6. Four selected cases were closely mimic cutaneous LE. It also remains also stained with colloidal iron for comparison. unclear whether chronic sun exposure may Chi-square and two-tailed t-tests were performed < contribute to mucin deposition to a certain between groups. A p-value of 0.05 was consid- degree. To our knowledge, study on the amount ered statistically significant. The specificities and of dermal mucin in these non-LE conditions is sensitivities of dermal mucin for the diagnosis of lacking in the current literature. LE were calculated using different cut-off com- Our objective was to address the above diagnos- bined scores. tic challenge by comparing the quantity and the distribution of dermal mucin in cutaneous LE Results to a variety of interface, perivascular, spongiotic and psoriasiform dermatitides as well as normal A total of 135 skin samples, including cutaneous skin without dermatitis. We also aimed to study LE (n = 35), GVHD (n = 8), EM/FDE (n = 9), the effect of chronic sun exposure on mucin LP (n = 15), PMLE (n = 11), urticaria (n = 8), deposition by comparing normal skin with and eczematous dermatitis (n = 8), psoriasis (n = 11), without solar elastosis. normal skin with solar elastosis (n = 16) and nor- mal skin without solar elastosis (n = 14) were selected. The LE cases included discoid (n = 8), subacute cutaneous (n = 7), systemic (n = 4), Materials and methods tumid (n = 13) and not-otherwise-specified After approval by the Institutional Review Board, (n = 3) subtypes. None of the patients in the the surgical pathology database at University of non-LE groups had known history of LE. Michigan was searched for ‘lupus erythemato- The mean combined (H&E + AB) mucin sus’, ‘tumid lupus’, ‘discoid lupus’, ‘subacute scores for all entities are summarized in Table 1. cutaneous lupus’, ‘systemic lupus’, ‘eczema’, Four specimens were superficial and were ‘psoriasis’, ‘lichen planus’ (LP), ‘graft vs. host excluded from the calculations for the deep disease’ (GVHD), ‘erythema multiforme’ (EM), reticular dermal compartment. Sixteen cases ‘fixed drug eruption’ (FDE), ‘urticaria’ and (11.9%) had a discrepancy of at least two score ‘polymorphous light eruption’ (PMLE) between points between H&E and AB in at least one com- years 2010 and 2014. All pathologic slides were partment. The p-values obtained from two-tailed retrospectively reviewed and correlated with t-tests between groups are shown in Table 2. clinical data (obtained from requisition form Significantly more mucin was present in both and/or electronic medical record) to confirm superficial and deep reticular dermis in LE when the original diagnoses. Cases with diagnos- compared to GVHD, EM/FDE, LP, urticaria, tic uncertainty were eliminated. ‘Eczematous psoriasis and normal skin (Fig. 1). However, no dermatitis’ refers to cases showing a primarily significant difference was found when compar- spongiotic pattern, including atopic dermatitis, ing LE with PMLE and eczematous dermatitis contact dermatitis, nummular dermatitis and in all three compartments (Figs 2 and 3). Mucin eczematous drug reaction. Normal skin samples in the papillary dermis failed to distinguish LE with and without evidence of photodamage from other entities. Normal photodamaged (solar elastosis) were obtained from the tip skin (with solar elastosis) showed significantly margins of wide local excisions performed for more mucin in the superficial reticular dermis melanoma and Merkel cell carcinoma. compared to normal non-photodamaged skin 723 Vincent & Chan Table 1. Mean combined (H&E + AB) mucin scores Table 2. Comparison of combined (H&E + AB) mucin scores (p-values from two-tailed t-tests) Superficial Deep Papillary reticular reticular Superficial Condition n dermis dermis dermis Papillary reticular Deep reticular dermis dermis dermis LE (all subtypes) 35 3.17 4.57 2.83 DLE 8 2.88 4.25 2.38 LE vs. GVHD 0.1353 0.0015 0.0027 SCLE 7 3.71 4.71 2.57 LE vs. EM/FDE 0.5910 0.0009 0.0019 SLE 4 3.00 3.75 2.25 LE vs. LP 0.9324 <0.0001 <0.0001 TLE 13 3.15 4.92 3.38 LE vs. PMLE 0.4670 0.3240 0.6733 NOS 3 3.00 4.67 3.00 LE vs. urticaria 0.9359 0.0417 0.0476 GVHD 8 4.00 2.50 1.13 LE vs. eczematous 0.5997 0.0580 0.1256 EM/FDE 9 2.89 2.67 1.22 LE vs. psoriasis 0.9824 0.0074 0.0019 LP 15 3.13 2.27 0.75 Photodamaged normal vs. 0.2413 0.0140 0.0821 PMLE 11 3.55 4.09 2.64 non-photodamaged Urticaria 8 3.13 3.38 1.75 normal Eczematous 8 2.88 3.50 2.00 LE vs. normal* 0.4383 <0.0001 <0.0001 Psoriasis 11 3.18 3.18 1.20 GVHD vs. normal* 0.0109 0.8506 0.9136 Normal, 16 3.13 3.06 1.44 EM/FDE vs. normal* 0.9096 0.8799 0.8668 photodamaged LP vs. normal* 0.5876 0.3438 0.1960 Normal, 14 2.71 2.07 0.86 PMLE vs. normal* 0.1429 0.0006 <0.0001 non-photodamaged Urticaria vs. normal* 0.6683 0.1107 0.1268 Eczematous vs. normal* 0.8912 0.0510 0.0331 AB, Alcian blue; DLE, discoid lupus erythematosus; EM, erythema Psoriasis vs. normal* 0.4765 0.1718 0.9275 multiforme; FDE, fixed drug eruption; GVHD, graft vs. host dis- ease; H&E, hematoxylin–eosin; LE, lupus erythematosus; LP, lichen AB, Alcian blue, EM, erythema multiforme; FDE, fixed drug eruption; planus; n, number of cases; NOS, not-otherwise-specified; PMLE, GVHD, graft vs.