Dermatopathology Trainee World Cup Abstract Presentations at the 28th Joint Meeting of the International Society of Dermatopathology, March 5–6, 2025, Orlando, Florida, USA

Histopathologic Spectrum of Lesions Arising from Anogenital Mammary-Like Glands: Fourteen-Year Institutional Experience Fiona Lane ([email protected]) Background: Anogenital mammary-like glands (AGMLG) mimic breast tissue histologically and may give rise to various types of benign lesions and malignant tumors with histopathologic features similar to breast lesions, including a subset of primary extramammary Paget Disease (EMPD). Objective: Describe the spectrum of lesions arising from AGMLG, through a retrospective review. Design: A retrospective review (2010–2024) of UCLA Department of Pathology and Laboratory Medicine database was performed to search for lesions that may arise from AGMLG. Results: A total of 100 patients (82 females and 18 males, 29–84 years) with lesions arising from AGMLG were identified. The majority of the lesions were malignant (51/100; 51%). EMPD was the most common (48/51; 94%), 9 of which had developed into invasive adenocarcinoma. Three cases showed adenocarcinoma (2 invasive and 1 in-situ), mammary gland type. The remaining cases were benign (49/100; 49%). The majority of benign lesions were hidradenoma papilliferum (38/49; 78%), 8 cases of nodular/mass-like lesions composed of AGMLG were present, and there was one case each of phyllodes tumor, tubular apocrine adenoma, and fibroadenoma. Conclusions: Most common neoplasms of AGMLG include EMPD and hidradenoma papilliferum, and a minor subset includes lesions/tumors that resemble breast tissue and neoplasms. Co-authors: Fiona Lane (University of California Los Angeles, Department of Pathology and Laboratory Medicine), Neda Moatamed, MD (University of California Los Angeles, Department of Pathology and Laboratory Medicine), and Yuna Kang, MD (University of California Los Angeles, Department of Pathology and Laboratory Medicine) Pain in the Palate: Vincent's Angina–A Forgotten Mimic of Angioinvasive Fungal Infection Richard Zhu ([email protected]) Background: Vincent's angina, or acute necrotizing ulcerative gingivitis (ANUG), is a rare, rapidly progressing necrotizing infection of the oral cavity characterized by sudden gingival necrosis, severe pain, spontaneous bleeding, and halitosis. It involves a polymicrobial profile, with a unique combination of anaerobic bacteria and spirochetes. Accurate differentiation from life-threatening conditions such as angioinvasive fungal infection is crucial, as angioinvasive fungal infection requires aggressive, sometimes morbid surgical debridement and antifungal therapy, while ANUG is managed with antibiotics and improved oral hygiene. Clinical Case: A 36-year-old female presented with severe oral pain, fever, foul breath, bilateral lymphadenopathy, and a necrotizing hard palate lesion. Initial bloodwork revealed a new diagnosis of HIV, so an urgent biopsy of the hard palate was performed to exclude angioinvasive fungus. Histopathology revealed sharply circumscribed necrosis with abundant bacteria, and no fungal elements. A treponemal immunohistochemical stain identified numerous spirochetes confirming the clinical suspicion of Vincent's Angina. Conclusion: This case underscores the importance of histopathological evaluation in diagnosing Vincent's angina, a once forgotten, but increasingly relevant clinical mimic of angioinvasive fungus in an age where syphilis is continuing to thrive. Co-authors: Richard Zhu (University of Saskatchewan, College of Medicine), and Katelynn Campbell (Saskatchewan Health Authority, Department of Pathology and Laboratory Medicine, University of Saskatchewan, College of Medicine) Tracing the Milk Line: A Case Series of Cutaneous Adenocarcinomas with Mammary-Type Histology Sarah Erem ([email protected]) Background: Adenocarcinomas with mammary-type differentiation (CAMam) are rare tumors, potentially arising from ectopic breast tissue along the embryonic milk line or anogenital mammary-like glands. Pathogenesis of this tumor type supports biomarker-based targeted therapy. Design: We present 7 cases of CAMam identified along the embryonic milk line. Metastases were excluded clinically and radiologically. Two board-certified pathologists with dermatopathology, breast, and OBGYN expertise reviewed slides and collected clinicopathological data. Results: All 7 cases occurred in females (ages 49–85, median 69) as solitary lesions (0.4–4.7 cm), with one in the axilla and 6 in the vulva. Histological subtypes included mucinous (4), ductal (2), and micropapillary (1), with one case of ductal carcinoma in-situ and 3 with focal pagetoid spread. All were GATA3-positive, with GCDFP or mammaglobin positivity. Biomarker profiles included ER/PR-positive (4), triple-positive (1), and triple-negative (2). NGS in 2 cases revealed GATA3, MAP3K1, and PIK3/AKT alterations with a 99% predicted breast origin. All underwent resection with negative margins, no lymph node involvement, or metastasis. Over 3–97 months, 3 patients received hormonal therapy, including CDK4/6 inhibitors and trastuzumab for HER2-positive disease, while both triple-negative patients died. Conclusions: CAMam, though uncommon, are significant due to their similarity to breast carcinoma, enabling biomarker-guided treatment. Co-authors: Anna Sarah Erem, MD (Emory University School of Medicine, Atlanta, GA), Shalon Liu, MD (Queen's University Kingston Health Sciences Center, ON, Canada), Atousa Ordobazari, MD (Moffit Cancer Center, Tampa, FL), Gulisa Turashvili, MD, PhD (Massachusetts General Hospital and Harvard Medical School, Boston, MA), and Geetha Jagannathan, MBBS (Emory University Hospitals, Atlanta, GA) Direct Immunofluorescence Testing for Cutaneous Vasculitis: A Retrospective Single-Center Cohort Study of 1043 DIF Specimens in Patients With Clinically Suspected Cutaneous Vasculitis Annie King ([email protected]) For cost-effectiveness in the evaluation of cutaneous vasculitis, some authors recently proposed truncating the standard direct immunofluorescence (DIF) testing panel to immunoglobulin (Ig)A, complement (C)3, and fibrin (1). However, the diagnostic contribution of each DIF reactant in cutaneous vasculitis is unknown (2). In this single-center retrospective study, we assessed predictive power (Area under curve of sensitivity vs. 1-specificity) of reactants individually and in combination to determine the optimal DIF panel for various cutaneous vasculitis subtypes. We reviewed all DIF specimens submitted with clinical concern for cutaneous vasculitis (08/2017-11/2023) and reviewed the corresponding EMR for final diagnosis. Of 1043 DIF specimens, 270 (25.8%) corresponded to a final diagnosis of cutaneous vasculitis. The combination of perivascular IgM, IgA and fibrin yielded the highest predictive power in cryoglobulinemia (80.3%), LCV (77.0%) and urticarial vasculitis (UV; 82.7%), while including all reactants resulted in the greatest predictive power for IgA vasculitis (96.3%). The combination of IgA, C3 and fibrin produced the lowest predictive power for UV (55.4%). IgM, C3 and fibrin yielded the lowest predictive power for cryoglobulinemia (57.6%). These results suggest that while a limited DIF panel may suffice for certain cutaneous vasculitis subtypes, it is suboptimal for others, such as UV and cryoglobulinemia. Co-authors: Frank Jing, MD (Mayo Clinic), Michelle Colbert, MD (Mayo Clinic), Donald E. Neal, MD (Mayo Clinic), Austin Todd, MS (Mayo Clinic), Heather D. Hardway, PhD (Mayo Clinic), Emma F. Johnson, MD (Mayo Clinic), Shruti Agrawal, MD (Mayo Clinic), Michael J. Camilleri, MD (Mayo Clinic), and Julia Lehman, MD (Mayo Clinic) Mycosis Fungoides With Unusual Immunophenotype: A 20-Year Retrospective Review Emily Hartsough ([email protected]) Objective: Mycosis fungoides (MF) is typically characterized by a CD4+CD8− immunophenotype (IP). Rare IP variants include CD8+, CD4−CD8− (DN), and CD4+CD8+ (DP) cases. While CD8+ MF has been shown to have a more indolent disease course compared to conventional MF, the clinical course of remaining rare IP variants is less clear. Methods: Clinical and pathologic variables of MF cases from 2003 to 2023 at 2 large academic institutions were retrieved. Results: 98 patients (age range: 11–88 years, median: 55) had unusual MF IPs during their disease course. The first diagnostic MF specimen was CD8+ in 43, DN in 6, DP in 5, and IP-variable in 44 patients. Of the 44 IP-variable cases, 3 switched between 3 IPs, 13 with CD4 <--> CD8, 15 with CD4+ <--> DN, 9 with CD4+ <--> DP, 3 with CD8+ <--> DP, and 1 with CD8+ <--> DN. Follow-up ranged from 0 to 273 months (median: 84). Among the subgroups, CD8+ had the best overall survival (OS), DN the worst OS, and DP and IP-variable with intermediate OS (log-rank P = 0.007). Conclusion: There appears to be a correlation between survival and MF IP, and CD4−CD8− shows the worst OS. Co-authors: Emily Mae Hartsough (Massachusetts General Hospital), Mia S. DeSimone (Brigham and Women's Hospital), and Mai P. Hoang (Massachusetts General Hospital) PRKCD:SERINC1 Novel Fusion in Recurrent Aneurysmal Dermatofibroma Mimicking Dermatofibrosarcoma Protuberans Michelle Zhu ([email protected]) Aneurysmal dermatofibroma (ADF) is a rare variant of dermatofibroma with blood-filled spaces and hemosiderin, at times mimicking angiosarcoma. Traditionally, ADF are considered benign entities with some potential to recur locally. However, recently there have been reports of rare cases metastasizing. In addition, fusion transcripts including PRKCD and LAMTOR1 or CD63 genes have been described. A 35-year-old woman presented with a nodule on her back diagnosed on biopsy as dermatofibroma. After 2 years patient recurred with a 5 cm, bleeding lesion. Histopathological examination revealed a proliferation of spindle cells with storiform pattern and increased mitotic activity. An initial diagnosis of Dermatofibrosarcoma Protuberans with fibrosarcomatous changes was rendered. A re-review of the case revealed interspersed blood lakes, foamy histiocytes and hemosiderin pigment. Tumor was focally positive for SMA, CD68 and F13a, CD34 showed peripheral positivity, and a diagnosis of recurrent ADF was rendered. Furthermore, RNA-based next generation sequencing assay detected a PRKCD:SERINC1 fusion. This is a novel translocation in ADF which is predicted to result in a chimeric protein fusing the membrane-binding part of SERINC1 with the catalytic domain of the PRKCD. We propose that the presence of these drivers may be associated with more aggressive biologic behavior. Co-authors: Alicia Goldenberg (Roswell Park Comprehensive Cancer Center), Norbert Sule (Roswell Park Comprehensive Cancer Center), Gary Mann (Roswell Park Comprehensive Cancer Center), and Aleodor A. Andea (Roswell Park Comprehensive Cancer Center) Differential Immune Profiles in Radiation-Induced Morphea and Radiation-Induced Fibrosis: The Role of IL-33 in Disease Pathogenesis Diogo Maia e Silva ([email protected]) Introduction: Radiation-induced morphea (RIM) is a painful, disfiguring complication of radiation therapy that typically arises months to years following treatment. While it is generally understood to be an inflammatory sclerosing process, the pathogenesis of RIM remains poorly elucidated. This study aims to investigate the role of the interleukin-33 (IL-33)/regulatory T cell axis in RIM and radiation-induced fibrosis (RIF), a related condition included in its differential diagnosis. Methods: A cohort of 18 age-matched RIM and 12 RIF post-radiation female breast skin tissue samples was analyzed. Sections were reviewed and immunohistochemical studies for CD3, forkhead box protein P3 (FoxP3), and IL-33 were performed and quantified in 3 high-power fields (HPF) per sample. Statistical significance was determined using two-tailed t-tests. Results: Fibroblast-derived nuclear IL-33 was significantly reduced in RIM compared with RIF (5.9 vs. 12.4 per HPF, P = 0.001). Lymphoplasmacytic infiltrates trended higher in RIM although no significant difference was observed in the abundance of T-cells (CD3+) or regulatory T-cells (FoxP3+) between the 2 conditions. Conclusion: The sclerosing phenotype of RIM may be less reliant on fibroblast-derived IL-33 compared to RIF. IL-33 may serve as a valuable immunohistochemical marker to distinguish RIM from RIF in clinical and pathological contexts, to guide management. Co-authors: Diogo Maia-Silva, MD, PhD (Pathology Service, Massachusetts General Hospital and Harvard Medical School, Boston, MA; and Pathology Service, Brigham and Women's Hospital and Harvard Medical School, Boston, MA), Dongyao Wang, PhD (Center for Cancer Immunology and Cutaneous Biology Research Center, Department of Dermatology and Center for Cancer Research, Massachusetts General Hospital and Harvard Medical School, Boston, MA; and Department of Hematology, the First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, China), Satoshi Horiba, MS (Center for Cancer Immunology and Cutaneous Biology Research Center, Department of Dermatology and Center for Cancer Research, Massachusetts General Hospital and Harvard Medical School, Boston, MA), Timothy R. Quinn, MD, CM (Pathology Service, Massachusetts General Hospital and Harvard Medical School, Boston, MA; and Massachusetts General Physicians Organization Dermatopathology Associates, Newton, MA), Shadmehr Demehri, MD, PhD (Center for Cancer Immunology and Cutaneous Biology Research Center, Department of Dermatology and Center for Cancer Research, Massachusetts General Hospital and Harvard Medical School, Boston, MA), and Rosalynn M. Nazarian, MD (Pathology Service, Massachusetts General Hospital and Harvard Medical School, Boston, MA) Diagnostic Yield of Direct Immunofluorescence Testing in Conjunctival Biopsy Specimens: A Retrospective Single-Center Cohort Study of 80 Specimens Katherine Holder ([email protected]) Objective: To assess the diagnostic yield of direct immunofluorescence testing (DIF) in conjunctival biopsy specimens. Methods: This single-center retrospective cohort study assessed reports from all consecutive conjunctival DIF specimens (August 22, 2017–November 30, 2023) and correlated results with patient characteristics extracted from the electronic medical record. Results: Of 80 conjunctival biopsy samples (79 patients), 7 (8.8%) yielded positive DIF results (linear IgG, IgA, and/or C3 deposition, n = 3; shaggy fibrinogen deposition, n = 4). Three patients (42.9%) with positive DIF results had multisite involvement compared to 11.1% (8/72) of those with negative DIF results. All 6 patients with positive DIF presented with clinical inflammation and scarring, whereas of those with negative DIF, 51/60 (83.6%) had clinical inflammation, and 60/65 (92.3%) had scarring. Furthermore, of the 5 positive DIF patients for whom ELISA was performed for serum bullous pemphigoid antibodies, 1 (20%) demonstrated positivity compared to 1/31 (3.2%) of the negative DIF patients. 3/7 (42.9%) positive DIF results were obtained from patients with systemic immunosuppression in contrast to 6/73 (8.2%) in the negative DIF group. Conclusion: Factors increasing the likelihood of a positive conjunctival DIF result included multi-site involvement, clinical evidence of scarring and inflammation, and circulating BP autoantibodies. Systemic immunosuppression appears not to negatively affect DIF yield. Co-authors: Katherine G. Holder, MD (Mayo Clinic Dermatology), Frank Jing, MD (Mayo Clinic Dermatology), Heather D. Hardway, PhD (Mayo Clinic Dermatology), Michael J. Camilleri, MD (Mayo Clinic Dermatopathology), and Julia S. Lehman, MD (Mayo Clinic Dermatopathology) Aicardi-Goutieres Syndrome: An Interferon-Mediated Autoinflammatory Disorder Lindsey Gaghan ([email protected]) A 17-year-old male presented with a history of developmental delay, impaired growth, spastic quadriparesis. He eventually developed digital ischemia and widespread necrotic ulcerations, necessitating frequent hospitalizations. Lab work revealed normal C3, C4, and amino acid levels, while interferon-signaling gene expression score was elevated. Punch biopsy of the cheek showed vacuolar interface dermatitis, lymphocytic vasculitis, prominent hyalinized fat necrosis with calcifications, and lobular lymphoplasmacytic inflammation. MRI brain showed diffuse basal ganglia calcifications and cortical atrophy. Genetic testing revealed 2 homozygous intronic polymorphisms in RNASEH2B, which is a new variant recently implicated in Aicardi-Goutières Syndrome. He failed several immunosuppressants and was started on tofacitinib. Aicardi-Goutières Syndrome is a rare genetic disease which presents in early infancy and is characterized by progressive encephalopathy, developmental delay, and basal ganglia calcifications. Alterations in one of several genes (including RNSASEH2B) results in inadequate removal of endogenous nucleic acids, triggering IFN-alpha mediated inflammation and production of autoantibodies against DNA and RNA. Biopsy findings mimic lupus erythematosus, morphea, or mixed connective tissue disease. Recent cases in the literature have shown a favorable response to JAK inhibitors, though early diagnosis and intervention is key to prevent irreversible damage. Co-authors: Lindsey Gaghan (Brown University Health), Jaclyn Anderson (Brown University Health), Lionel Bercovitch (Brown University Health), and Leslie Robinson Bostom (Brown University Health) Variable TRPS1 Expression in Squamous Cell Carcinoma: Influence of Sun Exposure Scott Wang ([email protected]) Objective: TRPS1 (trichorhinophalangeal type has as a potential marker of in its expression in cell carcinoma is in studies TRPS1 expression in The role of and in TRPS1 expression remains Methods: We invasive cases from database in n = and n = n = and the = Two pathologists TRPS1 from 0 to invasive ductal carcinoma as a positive Results: showed reduced TRPS1 expression compared to normal while or higher were while had focal and in TRPS1 Conclusion: findings reduced TRPS1 in from normal with from which showed TRPS1 These findings suggest a on TRPS1 study to these and role in Co-authors: of Pathology and Laboratory Medicine, Hospital), and of Pathology and Laboratory Medicine, Hospital) and in Syndrome: A Rare ([email protected]) A presented with a history of recurrent widespread Over this underwent several skin each which such as and early vasculitis. He was by with a diagnosis of lupus and started The patient was to for A biopsy showed to a diagnosis of with gene The patient eventually developed the associated with the This case the histopathologic of in a patient a the in diagnosis due to under While the presence of and vasculitis is presents with histopathologic one case of 2 patients with has histopathologic features This rare lymphocytic pattern underscores that may present with a spectrum and recurrent of unknown in an suspicion for Co-authors: Department of Dermatology), and Medical A Experience of Cutaneous A Case Series ([email protected]) Background: cell inhibitors, and Cutaneous in to of including conditions bullous pemphigoid and with Objective: cutaneous to inhibitors using Methods: We reviewed database from to patients showed cutaneous to We reviewed patient and clinical data. Results: Among cases 2 demonstrated (2 on 1 (2 2 3 bullous pemphigoid 1 and 1 ranged from 1 to 18 months, with All cases had tissue or peripheral Conclusion: inhibitors cutaneous with including mediated through the spectrum of these cutaneous in to early clinical and their diagnosis and guide treatment. Co-authors: Medical Center), Medical Center), Medical Center), Medical Center), and Medical Center) and in or a A Review of Two With and ([email protected]) and significant in and Tumor are common in and in This review 2 cases with features that potentially a new Two male a with a history of and a presented with in one the and and the in the and Histology and revealed malignant spindle cell neoplasms with nuclear and showed and positivity and but negative and testing identified in and The associated with These cases diagnostic where with The in and along with and the of or a new The results the role of in an with both patients a favorable response to targeted Co-authors: M. 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