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We report a case of bleomycin-Induced flagellate dermatitis. Our patient developed pruritic linear lesions 4 days after her first dose of bleomycin. A closed patch test was performed, and was negative. However, on rechallenge. the linear eruption recurred in the previously involved sites. and in new sites. within 24 h. Flagellate dermatitis is a characteristic reaction to bleomycin use, but varying histological features and clinical presentations may be seen. [ABSTRACT FROM AUTHOR]

Background: Mohs surgery of eyelid skin cancers requires detailed knowledge of anatomy for precise surgery and accurate evaluation of histology., Objective: To review the histology of the peritarsal eyelid using frozen sections as encountered intraoperatively by Mohs surgeons., Methods: The authors review the literature describing the anatomy and histology of the peritarsal eyelid from the lens of a Mohs surgeon. Histology from select Mohs cases is used to frame the discussion of the microanatomy of this region., Results: The peritarsal eyelids contain a unique mixture of skin, muscle, tarsus, glandular tissue, and conjunctiva. The histologic appearance of many of these structures differs from skin found outside of this anatomic region. Tumors of the eyelid and periocular region may mimic normal histologic structures found within the peritarsal eyelid., Conclusion: The peritarsal eyelids have unique anatomy and associated histologic structures. Knowledge of the detailed histoanatomy is required for confident execution of Mohs surgery in this anatomic region., (Copyright © 2024 by the American Society for Dermatologic Surgery, Inc. Published by Wolters Kluwer Health, Inc. All rights reserved.)

Melanoma of the nail apparatus is challenging to diagnose for both dermatologists and dermatopathologists. Misdiagnosis or delayed diagnosis of nail unit melanoma can have fatal consequences and legal ramifications. This review educates dermatopathologists on challenges and traps they should be aware of to avoid misdiagnosis of nail unit melanoma. We present illustrative difficult cases that introduce several themes regarding challenges in the diagnosis of nail unit melanoma: specimens with subtle histopathologic findings, challenges in immunoperoxidase interpretation, and how clinical knowledge and surgical procedural knowledge are mandatory to make the diagnosis. Dermatopathologists will be aware of when and how to suspect nail unit melanoma in unusual circumstances., (© 2023 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Few prospective studies have evaluated local recurrence rates (LRR) after excision of desmoplastic melanoma (DM); however, several retrospective studies have reported high LRR., Objective: To determine LRR after excision of DM and evaluate factors affecting LRR., Materials and Methods: Systematic review of the PubMed, Embase, and Web of Science databases was performed to identify studies reporting local recurrence after excision of DM with conventional wide local excision (WLE), Mohs micrographic surgery (MMS), or staged excision (SE). Meta-analysis was performed to calculate summary LRR and pooled risk ratios (RR)., Results: Literature search identified 4 studies evaluating MMS or SE (total n = 61 DM). 53 studies assessed WLE ( n = 3,080) and were analyzed quantitatively. The overall LRR after WLE of DM was 21% (95% CI, 0.16-0.28; n = 2,308). Local recurrence rate was higher with positive/unknown histologic excision margins (49%, 95% CI, 0.25-0.74; n = 91) versus negative histologic margins (11%, 95% CI, 0.07-0.17; n = 1,075; [ p < .01]). Neurotropism was also associated with increased LRR (RR, 1.79; 95% CI, 1.34-2.38, p < .01; n = 644)., Conclusion: DM has high LRR after WLE. Local recurrence risk was greatest with positive excision margins, indicating the importance of achieving negative microscopic margins. Greater study of MMS and SE for DM is required., (Copyright © 2023 by the American Society for Dermatologic Surgery, Inc. Published by Wolters Kluwer Health, Inc. All rights reserved.)

We call on dermatologists and dermatopathologists to include nail clipping histopathology as an essential component of the routine evaluation of melanonychia. This manuscript demonstrates a case where an adult woman with broad melanonychia of the right thumbnail declined a nail matrix biopsy, but was amenable to a nail clipping.The nail clipping showed pigmentation, melanocyte remnants, and small cavities in the nail plate. These features have been published previously by our group as a clue to nail unit melanoma within nail clippings.This patient was rapidly triaged for nail matrix biopsy, which demonstrated nail unit melanoma in situ. Every patient with melanonychia can benefit from a nail clipping by examination of the location of the pigmentation within the nail plate for surgical planning, and if melanocyte remnants are detected, the nail clipping also serves as a rapid triage mechanism for nail matrix biopsy to evaluate for nail unit melanoma. Fontana-stained sections will highlight the pigmentation in the nail plate, and its location in the nail plate can easily be described by the dermatopathologist. Nail clippings performed in the setting of clinically apparent melanonychia may show helpful histopathologic findings of pigmented fungi, hemorrhage, external pigmentation, features of other pigmented nail unit tumors, as well as other entities. Nail clipping histopathology can provide extensive information in the evaluation of melanonychia with minimal discomfort for a patient, and little disruption to a physician's clinic flow. With this additional case of a nail unit melanoma diagnosed after initial concern found in a nail clipping, as well as other information in the literature, it is clear that melanocyte remnants found in nail clippings are reliable concerning features related to nail unit melanoma in adults. With knowledge of these histopathologic features in nail clippings and the significance of melanocyte remnants, the dermatopathologist can play a crucial role in the use of a nail clipping as a life-saving diagnostic maneuver. Accordingly, given the potential benefit to patients in this setting, as well as other uses of a nail clipping in the evaluation of melanonychia, we call on dermatologists and dermatopathologists to innovate the routine evaluation of melanonychia through the routine employment of nail clippings for histopathologic evaluation., (© 2022 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Importance: A standardized pathology classification system for melanocytic lesions is needed to aid both pathologists and clinicians in cataloging currently existing diverse terminologies and in the diagnosis and treatment of patients. The Melanocytic Pathology Assessment Tool and Hierarchy for Diagnosis (MPATH-Dx) has been developed for this purpose., Objective: To revise the MPATH-Dx version 1.0 classification tool, using feedback from dermatopathologists participating in the National Institutes of Health-funded Reducing Errors in Melanocytic Interpretations (REMI) Study and from members of the International Melanoma Pathology Study Group (IMPSG)., Evidence Review: Practicing dermatopathologists recruited from 40 US states participated in the 2-year REMI study and provided feedback on the MPATH-Dx version 1.0 tool. Independently, member dermatopathologists participating in an IMPSG workshop dedicated to the MPATH-Dx schema provided additional input for refining the MPATH-Dx tool. A reference panel of 3 dermatopathologists, the original authors of the MPATH-Dx version 1.0 tool, integrated all feedback into an updated and refined MPATH-Dx version 2.0., Findings: The new MPATH-Dx version 2.0 schema simplifies the original 5-class hierarchy into 4 classes to improve diagnostic concordance and to provide more explicit guidance in the treatment of patients. This new version also has clearly defined histopathological criteria for classification of classes I and II lesions; has specific provisions for the most frequently encountered low-cumulative sun damage pathway of melanoma progression, as well as other, less common World Health Organization pathways to melanoma; provides guidance for classifying intermediate class II tumors vs melanoma; and recognizes a subset of pT1a melanomas with very low risk and possible eventual reclassification as neoplasms lacking criteria for melanoma., Conclusions and Relevance: The implementation of the newly revised MPATH-Dx version 2.0 schema into clinical practice is anticipated to provide a robust tool and adjunct for standardized diagnostic reporting of melanocytic lesions and management of patients to the benefit of both health care practitioners and patients.

Abstract: Insulin-derived amyloidosis (AIns) is a rare iatrogenic subtype of cutaneous amyloidosis occurring at frequent insulin injection sites. Here, we describe 2 cases of AIns accompanied by acanthosis nigricans (AN)-like changes, a rare finding which has been reported fewer than 5 times in the literature. We also report the first case of an AIns nodule being misdiagnosed as a keloid. Both of our patients presented with asymptomatic, hyperkeratotic, pigmented plaques at frequent insulin injection sites, and histopathologic examination showed (1) nodular aggregates of amyloid demonstrating apple-green birefringence with Congo red staining and (2) AN-like features, such as epidermal papillomatosis, hyperkeratosis, and hyperpigmentation. Accurate diagnosis of AIns is crucial, because repeated insulin injection into a nodule can impair glycemic control. However, misdiagnosis is common, as observed with our second patient, whose AIns nodule was misdiagnosed by an outside provider as a keloid, perhaps because of the presence of AN-like features. Our case report adds to the limited but growing body of literature on AIns and significantly increases the number of reported cases of AIns with AN-like features, an even rarer phenomenon., Competing Interests: The authors declare no conflicts of interest. Dr. Rosalie Elenitsas has no conflicts of interest relevant to this manuscript. However, for full disclosure: she has received royalties from Wolters Kluwer as a textbook editor., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Abstract: Cutaneous ganglioneuromas (GNs) are exceptionally uncommon tumors, and many reported cases describe association with overlying epidermal hyperplasia that may be interpreted as seborrheic keratosis (SK) or SK-like proliferation. We report 5 cases of cutaneous GN in adult patients; all of which were discovered incidentally in the immediate vicinity of epidermal hyperplasia. A review of the literature demonstrates the current-although likely imperfect-understanding of the etiopathogenesis of both SK and GN in the skin. We explore the putative pathophysiologies of other common, well-characterized skin lesions and, taking them into account, provide rationale for the coexistence of cutaneous GN with overlying SK and SK-like epidermal changes. However, we ultimately acknowledge a dilemma of causality and, given the rarity of their co-occurrence, objectively question whether occasional cameo appearances by GN lying subjacent to SK and SK-like hyperplasia may be due merely to chance., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Programmed cell death protein (PD-1) and programmed death-ligand 1 (PD-L1) inhibition checkpoint blockade leads to various cutaneous adverse reactions, including bullous pemphigoid and lichen-planus-like reactions. However, lichen planus pemphigoides (LPP), manifesting histopathologic features of both lichen planus and bullous pemphigoid, has more rarely been associated with immunotherapy., Methods: The clinical and histopathologic findings of three patients were examined, and a review of cases of LPP and bullous lichen planus secondary to PD-1 inhibitor therapy was performed., Results: Three patients (two with advanced non-small-cell lung adenocarcinoma and the third with metastatic breast cancer) presented with both lichenoid eruptions and bullae. Biopsy of the lesions revealed lichenoid tissue reactions in all three patients. Together with the histopathologic findings, direct immunofluorescence (DIF) showing linear C3 and IgG deposition and positive enzyme-linked immunosorbent assay (ELISA) showing BP180 positivity supported a diagnosis of LPP in two patients. The third patient in our series also showed confirmatory ELISA testing supporting LPP., Conclusions: Lichen planus pemphigoides is a distinct cutaneous toxicity to checkpoint inhibitor therapy illustrates a possible pathogenic mechanism and the importance of dermatopathology recognition to render an accurate diagnosis., (© 2022 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Competing Interests: The authors declare no conflicts of interest.

Competing Interests: The authors declare no conflicts of interest.

Vulvar malignant melanoma (VMM), although uncommon, comprises 5-10% of all vulvar malignancies. Local control is notoriously poor in VMM with recurrence rates of 30-50% compared with approximately 3% in cutaneous melanomas. We studied clinicopathologic features of 37 women with VMM, after reviewing three decades of clinical follow-up data in our institutional databases. Most patients were Caucasian (n = 35) with an average age at diagnosis of 60.6 years (range 23-83). The most common subtype was mucosal lentiginous melanoma (n = 25). We compared Kaplan-Meier survival curves of 31 patients defined by clinical and microscopic attributes using exact log-rank tests. Younger patients at diagnosis (23-64 years), those with thin melanomas (≤1 mm), and those with Clark's level II or III tumors had better 5-year survival rates than older patients (65-83 years) and those with thick melanomas (>1 mm) and those with Clark's level IV or V (P ≤ 0.05), respectively, by exact log-rank test. Local recurrence of melanoma occurred in 15 patients. Nine patients (24%) had eventual urethral involvement by malignant melanoma, and this feature was associated with significantly shorter survival (P = 0.036). Patients with urethral involvement had shorter median time to death and worse 5-year survival rates. Given that spread to the urethra is common in VMM and urethral recurrence is also associated with mortality, pathology excision specimens should be carefully reviewed with attention to urethral involvement as a potentially important prognostic factor., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Lymphomatoid papulosis (LyP) is a chronic skin condition, characterized by recurrent eruptions of papules and nodules with or without central necrosis that spontaneously resolve. This condition was originally described by Macaulay in 1968 as a self-healing rhythmical paradoxical eruption that was clinically benign yet histologically malignant.1 Clinically, it is defined by papules that wax and wane, are generally less than 1cm in diameter, and heal spontaneously after 6–8 weeks with subsequent scarring.2