Comparison of Digital Pathology and Light Microscopy Among Dermatology Residents: A Reappraisal Following Practice Changes.

BACKGROUND: Following transition to digital pathology for primary diagnosis at our institution, dermatology residents have reduced exposure to light microscopy. This study compares resident competency with light microscopy versus digital pathology following practice changes. METHODS: Twenty-one dermatology residents were administered a dermatopathology examination composed of 32 diagnoses evaluated using digital slides and 32 with light microscopy. Case difficulty was graded and balanced between modalities. Diagnostic accuracy was measured using the number of correct diagnoses for each modality. Participants were surveyed regarding their experience and preferences. RESULTS: Diagnostic accuracy was higher with digital pathology than light microscopy (22/32 vs. 18/32, P < 0.001). Diagnostic accuracy with digital pathology increased with years of training, but accuracy with light microscopy did not. Residents with previous light microscopy experience achieved an average score of 19/32 on glass, as compared with 10/32 for those without experience (P = 0.039). Digital pathology was preferred over light microscopy (18/21, 85.7%). CONCLUSIONS: Trainees had better diagnostic proficiency with digital pathology and preferred this modality. Most practices at this time continue to use light microscopy. Therefore, we need to maintain proficiency in microscopy during training while concurrently preparing trainees for a digital future.

Fusion-driven cutaneous and superficial mesenchymal and adnexal tumors-A clinicopathologic and molecular study of 15 cases, including a novel case of ACTB::ZMIZ2-rearranged adnexal carcinoma.

BACKGROUND: While the list of fusion-driven soft tissue neoplasms is expanding rapidly, their importance among cutaneous and superficial mesenchymal and adnexal neoplasms remains poorly understood. This challenge is especially evident in cases with ambiguous histopathology that are difficult to classify based on morphology. AIMS: Our goal was to investigate the benefits of next-generation sequencing in diagnosing complex cutaneous neoplasms. MATERIALS & METHODS: Departmental archives were searched for fusion-driven cutaneous neoplasms. Slides were retrieved and clinical information including follow-up was obtained. RESULTS: Fifteen cases occurred in eight female and seven male patients, with a median age of 26 years (range: 1-83) at diagnosis. Tumors involved the extremities (9), scalp (5), and head and neck (1). Predominant features included myoepithelial (5), nested spindled with clear cytoplasm (2), atypical adnexal/squamoid (2), small round blue cell (2), cellular spindled (3), and fibrohistiocytic morphology (1). Most frequently encountered fusions involved EWSR1 (6) fused to ERG (1), FLI1 (1), CREB1 (2), CREM (1), PBX3 (1), followed by PLAG1 (4) with LIFR (2), TRPS1 (1) and CHCHD7. Additional fusions encountered were YAP1::NUTM1, EML4::ALK, SS18::SSX1 (2), and a novel fusion: ACTB::ZMIZ2. Integration of histologic features and molecular findings led to final diagnoses of primary cutaneous Ewing sarcoma (2), soft tissue myoepithelioma (4), cutaneous syncytial myoepithelioma (1), cutaneous adnexal carcinoma (1), porocarcinoma (1), inflammatory myofibroblastic tumor (1), synovial sarcoma (2), clear cell sarcoma (2), and angiomatoid fibrous histiocytoma (1). DISCUSSION AND CONCLUSION: Our results show that fusion testing can be a helpful diagnostic tool, especially in cases with unusual or uncommon morphology in superficial sites. Furthermore, it can allow for the identification of potential therapeutic targets in some instances.

Characterization and Management of Amicrobial Pustulosis of the Folds, Aseptic Abscess Syndrome, Behçet Disease, Neutrophilic Eccrine Hidradenitis, and Pyostomatitis Vegetans-Pyodermatitis Vegetans.

Neutrophilic dermatoses are a broadly heterogeneous group of inflammatory skin disorders. This article reviews 5 conditions: amicrobial pustulosis of the folds, aseptic abscess syndrome, Behçet disease, neutrophilic eccrine hidradenitis, and pyostomatitis vegetans-pyodermatitis vegetans.The authors include up-to-date information about their epidemiology, pathogenesis, clinicopathologic features, diagnosis, and management.

Neutrophilic eccrine hidradenitis: a retrospective study.

BACKGROUND: Neutrophilic eccrine hidradenitis (NEH) is a benign neutrophilic dermatosis not well recognized beyond an association with malignancy. Although the disease is commonly reported in adults with malignancy, this association is uncommon in children. The diagnosis of NEH is predominantly based on histologic findings to exclude alternative diagnoses for adults, but biopsy is not usually required for children. METHODS: A retrospective study was performed of adult and pediatric patients diagnosed with NEH at three Mayo Clinic sites from January 1, 1992, to January 1, 2022. The aim of this study was to elucidate risk factors for NEH and its clinical characteristics, treatment options, and natural course. Clinical information and pathologic results were collected from health records. Available pathologic slides were reviewed with a dermatopathologist. RESULTS: Of 47 patients identified, 33 had either histologic or clinical confirmation of the diagnosis; 21 were adults (64%), and 12 were children (36%). Most adults (16/21; 76%) had underlying malignancy and received chemotherapy. Five adults (24%) were classified as having idiopathic NEH, and they were younger and had higher NEH recurrence rates than the other adults. Only one pediatric patient (8%) had underlying malignancy. For 10 children (83%), NEH was preceded by strenuous activity. Initial findings of idiopathic NEH were palmoplantar eruptions for both adult and pediatric patients, whereas malignancy-associated NEH commonly involved the face and axillae. CONCLUSIONS: Among adults, NEH is commonly associated with malignancy and chemotherapy. Among children, idiopathic NEH occurs primarily after overexertion, and malignancy is highly unlikely to be the cause of NEH.

Histopathologic features predictive of perivascular deposition of IgA on direct immunofluorescence in cases of leukocytoclastic vasculitis: A retrospective study of 112 specimens.

IgA vasculitis is a small-vessel vasculitis subtype with increased risk of systemic involvement. We aimed to investigate if any light-microscopic features can predict the presence of perivascular granular IgA deposits on direct immunofluorescence (DIF) microscopy. We performed a retrospective search of cutaneous pathology reports from our internal and consultation practice (January 1, 2010-October 5, 2021) with a diagnosis of leukocytoclastic vasculitis and accompanying DIF. A blinded dermatopathologist reviewed standard microscopy slides for predetermined histopathological features. Fifty-six biopsies (48 patients) and 56 biopsies (42 patients) met inclusion criteria for IgA+ and IgA-, respectively. The presence of eosinophils and mid and deep dermal inflammation were statistically more associated with IgA- (41/56 [73.2%] and 31/56 [55.4%], respectively) than IgA+ cases (28/56 [50.0%] and 14/56 [25.0%]; p = 0.049 and 0.006, respectively, chi-squared test). Other microscopic criteria recorded were not significantly different between the two groups (p > 0.05, chi-squared and Fisher's exact tests). In this retrospective study of 112 cases, we found that while the absence of eosinophils and absence of mid- and deep inflammation were correlated with increased likelihood of IgA perivascular deposition on DIF, no other histopathological features on light microscopy tested could reliably predict the presence of IgA perivascular deposition on DIF. Therefore, DIF remains a necessary component for the accurate diagnosis of cutaneous IgA vasculitis.

Histopathology of autoimmune bullous dermatoses: what's new?

Autoimmune bullous dermatoses are characterized by the presence of tissue-bound and often circulating pathogenic autoantibodies targeting structural components of the skin and/or mucous membranes. The diagnostic workup for this heterogeneous group of disorders consists of a multi-step process, of which the light microscopic examination is a crucial component. This review is organized following a classification scheme that is based on two main histopathologic features, namely level of intraepithelial split and composition of the inflammatory infiltrate. Overall, we aim to place emphasis on the histopathologic clues that can assist pathologists in differential diagnosis and review the updates in the literature.

Impact of adding an IgG4 conjugate to routine direct immunofluorescence testing for subepithelial and intraepithelial autoimmune blistering disorders.

BACKGROUND: Certain autoimmune bullous dermatoses are mediated by autoantibodies of the IgG4 subclass. We determined the diagnostic impact of adding IgG4 to our conventional direct immunofluorescence (DIF) panel. METHODS: For all cases submitted to our referral laboratory for DIF over 1 month (n = 630), we performed IgG4 testing and collected consecutive biopsy specimens showing definite or indeterminate linear or cell-surface deposition of IgG, IgG4, and/or C3. On retrospective blinded review, we classified the pattern and whether the findings were definite, indeterminate, or negative. When present, substantial background staining was recorded. RESULTS: Seventy DIF specimens met the inclusion criteria. Of 22 (31.4%) specimens equivocal for linear or cell-surface deposition, 9 (40.9%) had definitive IgG4 findings, either linear (3 of 14 equivocal linear cases; 21.4%) or cell-surface (6 of 8 equivocal cell-surface cases; 75.0%). Background deposition was substantial in 14 cases (20.0%) for IgG but in none for C3 or IgG4. CONCLUSION: IgG4 allowed the classification of over 40% of DIF cases that were otherwise equivocal by IgG and C3. IgG4 staining showed lower levels of non-specific background staining than IgG or C3. IgG4 appears to contribute most value in cases with cell-surface deposition or with equivocal linear IgG deposition and negative C3 results.

Retrospective analysis of 450 emergency department dermatology consultations: An analysis of in-person and teledermatology consultations from 2015 to 2019.

INTRODUCTION: Dermatologic complaints are a common reason for emergency department visits. METHODS: Retrospective chart review from 1 January 2015 to 31 December 2019. Patients in the Mayo Clinic Emergency Department receiving dermatology consultation were included. RESULTS: Dermatitis (24.7%, n = 113), infection (20.4%, n = 93), and drug reaction (10.3%, n = 47) accounted for the majority of diagnoses. Emergency department providers often provide no diagnosis (38%) or a differential diagnosis (22%), and dermatology consultation frequently alters diagnosis (46%) and treatment (83%). Patients receiving in-person consultations are admitted more frequently than those receiving teledermatology consultations (40% vs. 16%, p < 0.001). Primary diagnostic concordance with subsequent dermatology evaluation is high for in-person (94%) and teledermatology (88%) consultations. DISCUSSION: This is the largest study of emergency department dermatology consultations in the United States and the first to compare in-person and teledermatology emergency department consultation utilization in clinical practice. These modalities are utilized in a complementary fashion at our institution, with severe dermatologic diagnoses seen in-person. The valuable role of emergency department dermatologists is highlighted by frequent changes to diagnosis and treatment plans that result from dermatology consultation. Furthermore, our data suggest that teledermatology is an effective modality with the potential to expand access to dermatologic expertise in the emergency department setting.

Retrospective analysis of 578 inpatient dermatology consultations in hematology and hematopoietic stem cell transplant patients.

BACKGROUND: Hospitalized patients with hematologic malignancies are medically complex and commonly affected by dermatologic conditions. METHODS: Retrospective chart review from January 1, 2014, to December 31, 2018, at Rochester Methodist Hospital (Rochester, Minnesota, USA). Patients hospitalized on hematology and BMT services receiving dermatology consultation were included. RESULTS: In all, 578 consultations (63% male, median age 61 years) were reviewed. Drug reactions (22%), infection (17%), and malignant neoplasm (10%) accounted for nearly half of diagnoses. Exanthematous drug reaction (10%), graft-versus-host disease (7%), and lymphoma or leukemia cutis (6%) were the commonest individual diagnoses. There were significantly more drug reactions in severe neutropenia (33.2% vs. 15.0%), neutrophilic dermatoses in myeloid neoplasm (5.2% vs. 0.3%), and viral infection in lymphoid neoplasm (8.3% vs. 1.2%). Consultation frequently altered treatment (68%), diagnostic workup (63%), and the primary service's initial diagnostic impression (53%). Biopsies were performed in 52% of consultations and helped secure a diagnosis 73% of the time. A total of 16.4% of consultations did not receive a definitive final diagnosis, and 18.5% were resolved in one visit. CONCLUSION: This is the largest study to date of hospital dermatology consultation in hematology patients. Biopsies are utilized frequently and are diagnostically useful. The complexity of this patient population is evidenced by the fact that a final diagnosis remains elusive in a number of cases despite the multiple visits required for the vast majority of consultations. Nevertheless, dermatology consultation alters diagnosis and treatment in the majority of patients, highlighting the critical role dermatologists have in the care of these patients.

Subepithelial autoimmune bullous dermatoses disease activity assessment and therapy.

Subepidermal (subepithelial) autoimmune blistering dermatoses are a group of rare skin disorders characterized by the disruption of the dermal-epidermal junction through the action of autoantibodies. The fourth article in this continuing medical education series presents the current validated disease activity scoring systems, serologic parameters, treatments, and clinical trials for bullous pemphigoid, mucous membrane pemphigoid, epidermolysis bullosa acquisita, bullous systemic lupus erythematosus, anti-p200 pemphigoid, linear IgA bullous dermatosis, and dermatitis herpetiformis.

Subepithelial autoimmune blistering dermatoses: Clinical features and diagnosis.

Subepithelial autoimmune blistering dermatoses are a group of rare skin disorders that are characterized by the disruption of the dermal-epidermal junction through the action of autoantibodies. The third article in this continuing medical education series explores the background, epidemiology, clinical features, and diagnostic criteria of each of the major subepithelial autoimmune blistering dermatoses, including bullous pemphigoid, pemphigoid gestationis, lichen planus pemphigoides, mucous membrane pemphigoid, linear IgA bullous dermatosis, and dermatitis herpetiformis.

Intraepithelial autoimmune blistering dermatoses: Clinical features and diagnosis.

Intraepithelial autoimmune blistering dermatoses are a rare group of skin disorders characterized by the intraepithelial disruption of intercellular connections through the action of autoantibodies. The first article in this continuing medical education series explores the background, epidemiology, clinical features, and diagnostic criteria of each of the major intraepithelial autoimmune blistering dermatoses, including pemphigus foliaceus, pemphigus erythematosus, pemphigus herpetiformis, fogo selvagem, pemphigus vulgaris, pemphigus vegetans, drug-induced pemphigus, IgA pemphigus, IgG/IgA pemphigus, and paraneoplastic pemphigus/paraneoplastic autoimmune multiorgan syndrome.

Intraepithelial autoimmune bullous dermatoses disease activity assessment and therapy.

Intraepithelial autoimmune blistering dermatoses are a rare group of skin disorders characterized by disruptions of inter-keratinocyte connections within the epidermis through the action of autoantibodies. The second article in this continuing medical education series presents validated disease activity scoring systems, serologic parameters of disease, treatments, and clinical trials for pemphigus and its subtypes.

Kaposi sarcoma misdiagnosed as granuloma annulare: A case of mistaken identity.

The microscopic features of patch stage Kaposi sarcoma (KS) and interstitial granuloma annulare (GA) may be difficult to differentiate, because both may exhibit a subtle "busy" dermis due to infiltration of spindled cells between collagen bundles. The clinical distinction is particularly challenging in human immunodeficiency virus (HIV)-affected individuals, as the incidence of GA appears to be greater in the HIV-infected population. KS is the most common neoplasm in this population. Despite the significant decrease in the incidence of KS since the advent of highly active antiretroviral therapy (HAART), KS tends to occur with late onset and indolent progression in patients with preserved immune function and minimal viral load. We present a 47-year-old homosexual HIV-positive man, under virologic and immunologic control on long-term HAART therapy, with a 5-year history of progressive red-brown patches and plaques on the legs, feet, hands, and trunk. Prior skin biopsy specimens were interpreted as interstitial GA. Histopathology on new skin biopsy specimens along with review specimens supported the diagnosis of plaque and patch stages of KS, respectively, supported by immunohistochemical expression of human herpes virus-8 (HHV-8). This case underscores the importance of maintaining a high suspicion for KS in progressive, treatment-recalcitrant skin lesions, particularly in HIV-infected individuals.