Context.— Fatal dermatologic diseases and ones with high morbidity can occur in the inpatient setting. In such cases, prompt and accurate assessment of a bedside skin biopsy is required. This may be challenging for many pathologists who are not familiar with the complexity of skin pathology and skin terminology within the fields of dermatopathology and dermatology. Objective.— To provide the pathologist with a practical, up-to-date, and “must-know” reference guide on dermatologic urgencies and emergencies from a real-world perspective, highlighting diagnostic pearls, diagnostic pitfalls, and commonly encountered practice gaps. This review will focus on key diseases with which every pathologist should be familiar, including angioinvasive fungal infections, Stevens-Johnson syndrome/toxic epidermal necrolysis, staph-scalded-skin syndrome, acute graft-versus-host disease, bullous pemphigoid, calciphylaxis, Sweet syndrome and its histiocytoid variant, pyoderma gangrenosum, and leukocytoclastic vasculitis, as well as those in their clinical and histopathologic differential. Data Sources.— This review is based on peer-reviewed literature and our personal experiences with these diseases at major academic institutions, including one where a large number of stem cell transplants are performed. This review is unique as it represents collaborative expert opinion from both a dermatopathology and a dermatology standpoint. Conclusions.— This review outlines the critical role that the pathologist plays in the outcomes of patients with dermatologic urgencies and emergencies. Improved patient care will result from prompt and accurate histopathologic diagnoses as well as an open line of communication with the dermatologist.

Biphasic lesions comprised of melanocytic and epithelial components are rare entities believed to arise either as a collision of 2 histologically distinct lesions in the same anatomic location or as a singular progenitor tumor differentiating along 2 differing lineages. Regardless of mechanism of origin, these tumors present unique challenges in pathologic interpretation and in determining appropriate measurements, which assigns subsequent prognosis to the patient. We present 4 tumors of melanoma co-existing with basal cell carcinoma (BCC) and discuss relevant literature regarding these biphasic entities. Patients consisted of 3 males and 1 female, ranging in age from 62 to 93, with lesions located on the shoulder, frontal scalp, forearm and nose. Three of 4 lesions showed melanoma cells limited to BCC tumor lobules, without evidence of direct dermal invasion by melanoma cells, raising the question of whether or not these tumors should be classified as in situ or invasive melanoma. These cases highlight the complexity that such lesions pose to dermatopathologists, in terms of their uncertain origin and variable microscopic appearance. In the absence of data regarding outcomes for these tumors (given their rarity), it is important to utilize a case-by-case approach, with careful clinical correlation and appropriate use of ancillary techniques.

The chapter provides a review of primary cutaneous malignant lymphoid infiltrates. The first portion of the chapter addresses the T cell lymphomas, beginning with mycosis fungoides and its myriad variants. More esoteric and less common forms of T cell lymphoma follow. The chapter then moves on to malignant B cell infiltrates, which much less frequently affect the skin. Secondary involvement of the skin by systemic lymphoma is not covered in this chapter.

No abstract

Objective:Rare disease Background:During the COVID-19 pandemic, the incidence of opportunistic infections, including fungal infections, has increased. Blastomycosis is caused by inhalation of an environmental fungus, Blastomyces dermatides, which is endemic in parts of the USA and Canada. This case report is of a 44-year-old man from the American Midwest who presented with disseminated blastomycosis infection 3 months following a diagnosis of COVID-19. Case Report:Our patient initially presented to an outpatient clinic with mild upper-respiratory symptoms. He tested positive for SARS-CoV-2 via polymerase chain reaction (PCR). Three months later, he presented to our emergency department due to some unresolved COVID-19 symptoms and the development of a widely disseminated, painful rash of 1-week duration. A positive Blastomyces urine enzyme immunoassay was the first indication of his diagnosis, which was followed by the identification of the pathogen via fungal culture from bronchoscopy samples and pathology from lung and skin biopsies. Given the evidence of dissemination, the patient was treated with an intravenous and oral antifungal regimen. He recovered well after completing treatment. Conclusions:The immunocompetent status of patients should not exclude disseminated fungal infections as a differential diagnosis, despite the less frequent manifestations. This is especially important when there is a history of COVID-19, as this may predispose once-healthy individuals to more serious disease processes. This case supports the recent recommendations made by the U.S. Centers for Disease Control and Prevention (CDC) for increased vigilance regarding fungal infections in patients with a history of COVID-19.