Association between COVID-19 vaccination and bullous pemphigoid - a case series and literature review.

Bullous pemphigoid is an acquired autoimmune blistering dermatosis that is commonly associated with high morbidity and mortality. New-onset bullous pemphigoid following vaccinations has rarely been reported in the literature. We report two cases of new-onset bullous pemphigoid after COVID-19 vaccination followed by a brief literature review. Twenty-six cases were included in our analysis. Our cases support that new-onset bullous pemphigoid may develop following COVID-19 vaccinations. Entering a period of clinical remission before subsequent COVID-19 vaccinations in addition to close follow-up should be considered to lessen the risk of recurrences or exacerbations.

Emergence of cutaneous Rosai-Dorfman disease during immunosuppressive treatment of follicular B-cell lymphoma: A case report.

BACKGROUND: Sinus histiocytosis with massive lymphadenopathy, also known as Rosai-Dorfman disease, is a rare proliferation of non-Langerhans histiocytes. Cutaneous Rosai-Dorfman disease is a rare subtype of Rosai-Dorfman disease limited to the skin with variable clinical presentation. CASE SUMMARY: A 59-year-old female with a history of osteoarthritis, hypothyroidism, and follicular B-cell lymphoma presented with pruritic, erythematous, dome-shaped papules that developed while on chemotherapy treatment. During cutaneous disease progression, the patient was further diagnosed with myelodysplastic syndrome. Histology review revealed patchy staining for S100 in the CD68+ histiocytes within the dermis with no enlarged histiocytes or emperipolesis. Given the absence of other findings, this was interpreted as cutaneous Rosai-Dorfman disease. CONCLUSION: There is still little known about the aetiology and pathogenesis of cutaneous Rosai-Dorfman disease. Non-specific immunohistochemistry in the midst of lymphoma, immunosuppressive treatments, and myelodysplastic syndrome produced a blurred diagnostic picture and delayed appropriate treatment, highlighting the diagnostic challenges of cutaneous Rosai-Dorfman disease.

Benign spindle cell lesions of the breast: a diagnostic approach to solitary fibrous tumour, nodular pseudoangiomatous stromal hyperplasia and nodular fasciitis.

Benign spindle cell lesions of the breast include neoplastic and reactive entities that are diagnostically challenging given their rarity and similar histomorphology. Accurate diagnosis on percutaneous core biopsy within this category is essential as some lesions require excision and surveillance, whereas others may be observed. We present three cases of rare benign spindle cell lesions of the breast that reflect the diversity of this group: solitary fibrous tumour, nodular pseudoangiomatous stromal hyperplasia and nodular fasciitis. Through these cases, we discuss the associated differential diagnosis and demonstrate how emerging ancillary studies can be integrated into a diagnostic approach. We highlight distinctive clinical and histopathological features and summarise recent updates to the clinical management of these lesions. An organised approach to the broad differential of spindle cell lesions is essential for appropriate diagnosis and treatment.

Case Report: Diagnosis of a Rare Plaque-Like Dermal Fibroma Successfully Treated With Mohs Surgery.

BACKGROUND: CD34-positive plaque-like dermal fibroma (PDF) is a poorly characterised benign dermal neoplasm that has a wide differential diagnosis. It can be mistaken for other entities on superficial biopsy and be overtreated, leading to unnecessary worry and extensive surgery. OBJECTIVE: To report on an uncommon presentation of this entity, the histopathologic differential diagnosis of PDF, and a novel treatment method. METHODS: Clinical and histopathological information was obtained for a PDF lesion on a 75-year-old man. RESULTS: On superficial biopsy, the PDF lesion was misinterpreted as a possible neurothekeoma. Successful Mohs surgery and genetic testing confirmed the diagnosis of PDF, and the patient received appropriate tissue-sparing surgical management. CONCLUSION: This case adds to our current knowledge about PDF and highlights the importance of early recognition of these lesions to direct appropriate diagnostic testing (full-thickness biopsy) and management. This case confirms successful management with Mohs surgery.

Clinical impact of mutation fraction in epidermal growth factor receptor mutation positive NSCLC patients.

BACKGROUND: We examined clinical outcomes in a population-based cohort of EGFR mutant advanced NSCLC patients, exploring the potential role of factors including tumour EGFR mutation fraction and cellularity in predicting outcomes. METHODS: A cohort of patients with EGFR mutant advanced NSCLC was identified (N =2 93); clinical outcomes, pathologic and treatment details were collected. Tumour response was determined from radiology and clinical notes. Association between demographic and pathologic variables EGFR TKI response, time to treatment failure (TTF) and overall survival (OS) was examined using logistic regression and proportional hazards regression. EGFR TKI response rates were summarised by percent mutation fraction to explore their association. RESULTS: Higher mutation fraction was associated with greater EGFR TKI response rate (odds ratio 1.58, 95% CI = 1.21-2.07, P = 0.0008), longer TTF (hazard ratio 0.80, 95% CI = 0.68-0.92, P = 0.003) and better OS (hazard ratio 0.81, 95% CI = 0.67-0.99, P = 0.04). However, even in patients with ⩽ 5% mutation fraction, response rate was 34%. Females had longer TTF (P = 0.02). CONCLUSIONS: EGFR mutation fraction in tumour samples was significantly associated with response, TTF and OS. Despite this, no lower level of mutation fraction was detected for which EGFR TKI should be withheld in those with activating EGFR mutations.

Lymphocytic panniculitis: an algorithmic approach to lymphocytes in subcutaneous tissue.

The diagnosis of panniculitis is a relatively rare occurrence for many practising pathologists. The smaller subset of lymphocyte-predominant panniculitis is further complicated by the diagnostic consideration of T cell lymphoma involving the subcutaneous tissue, mimicking inflammatory causes of panniculitis. Accurate classification of the panniculitis is crucial to direct clinical management as treatment options may vary from non-medical therapy to immunosuppressive agents to aggressive chemotherapy. Many diseases show significant overlap in clinical and histological features, making the process of determining a specific diagnosis very challenging. However, with an adequate biopsy including skin and deep subcutaneous tissue, a collaborative effort between clinician and pathologist can often lead to a specific diagnosis. This review provides an algorithmic approach to the diagnosis of lymphocyte-predominant panniculitis, including entities of septal-predominant pattern panniculitis (erythema nodosum, deep necrobiosis lipoidica, morphea profunda and sclerosing panniculitis) and lobular-predominant pattern panniculitis (lupus erythematous panniculitis/lupus profundus, subcutaneous panniculitis-like T cell lymphoma, cutaneous γ-δ T cell lymphoma, Borrelia infection and cold panniculitis).

Sample features associated with success rates in population-based EGFR mutation testing.

INTRODUCTION: Epidermal growth factor receptor (EGFR) mutation testing has become critical in the treatment of patients with advanced non-small-cell lung cancer. This study involves a large cohort and epidemiologically unselected series of EGFR mutation testing for patients with nonsquamous non-small-cell lung cancer in a North American population to determine sample-related factors that influence success in clinical EGFR testing. METHODS: Data from consecutive cases of Canadian province-wide testing at a centralized diagnostic laboratory for a 24-month period were reviewed. Samples were tested for exon-19 deletion and exon-21 L858R mutations using a validated polymerase chain reaction method with 1% to 5% detection sensitivity. RESULTS: From 2651 samples submitted, 2404 samples were tested with 2293 samples eligible for analysis (1780 histology and 513 cytology specimens). The overall test-failure rate was 5.4% with overall mutation rate of 20.6%. No significant differences in the failure rate, mutation rate, or mutation type were found between histology and cytology samples. Although tumor cellularity was significantly associated with test-success or mutation rates in histology and cytology specimens, respectively, mutations could be detected in all specimen types. Significant rates of EGFR mutation were detected in cases with thyroid transcription factor (TTF)-1-negative immunohistochemistry (6.7%) and mucinous component (9.0%). CONCLUSIONS: EGFR mutation testing should be attempted in any specimen, whether histologic or cytologic. Samples should not be excluded from testing based on TTF-1 status or histologic features. Pathologists should report the amount of available tumor for testing. However, suboptimal samples with a negative EGFR mutation result should be considered for repeat testing with an alternate sample.