Pseudocarcinomatous Sweet syndrome, 2022. ncbi.nlm.nih.gov/pmc/articl...
A case of the rare Sweet’s syndrome variant, pseudocarcinomatous Sweet’s syndrome. This variant may be misdiagnosed as the skin cancer, squamous cell carcinoma.
On biopsy, pseudocarcinomatous Sweet’s syndrome can show a neutrophilic dermal infiltrate (lots of neutrophils in the dermal skin layer), and pseudoepitheliomatous hyperplasia – pronounced thickening of the skin due to proliferation of all layers of the epidermis with irregular elongation of the rete ridges/pegs (rete pegs are intermittent regular protrusions of the outermost skin layer (epidermis) into the underlying skin layer (dermis)). Pseudoepitheliomatous hyperplasia can be seen in chronic inflamed skin lesions, and mimic a well-differentiated (keratoacanthoma-type) squamous cell carcinoma.
Biopsy won’t show certain features found in squamous cell carcinoma, such as a prominent dyskeratosis (abnormal keratinization occurring prematurely within individual cells or groups of cells below the stratum granulosum (granular layer of skin). Keratinization is a process by which keratin hardens). Keratinocyte skin cells are major building blocks of the epidermis. They make keratin, a protein that provides strength to skin, hair, and nails.
IMP! Sufficient sample of dermis needed in order to distinguish between pseudocarcinomatous Sweet’s syndrome and squamous cell carcinoma.
“Pseudocarcinomatous Sweet syndrome (pSS) is a rare histopathologic variant of acute febrile neutrophilic dermatosis that may clinically and histologically mimic squamous cell carcinoma (SCC).”
“A 65-year-old female with recurrent acute myeloid leukemia (AML) treated with the FLT3 inhibitor gilteritinib presented to the emergency department with a 4-day history of worsening facial lesions, rapidly increasing in size and number.”
“Examination revealed a large violaceous, crusted plaque on the left cheek, several smaller pinkish-purple crusted papules scattered on the cheek and left temple, and a firm subcutaneous mass with overlying ill-defined erythema on the left upper chest. Of note, 1 month prior she was admitted with fever and submandibular erythema and edema, diagnosed as possible differentiation syndrome secondary to gilteritinib, although she did not have enough clinical features to establish the diagnosis. She improved with a 3-week oral dexamethasone taper, which ended 13 days prior to this presentation. When these new facial lesions appeared, oncology admitted her to the hospital for IV dexamethasone and consulted inpatient teledermatology service.”
“Punch biopsies from the left cheek revealed complex epidermal hyperplasia, initially interpreted as SCC by general pathology. On reevaluation by dermatopathology, a neutrophilic dermal infiltrate with a differential of infectious process versus pSS was diagnosed.”
“Approximately 20% of all SS cases are associated with malignancy, most commonly AML. pSS is a rare subtype of SS characterized by pseudoepitheliomatous epidermal hyperplasia (PEH). To our knowledge, only 1 other case of pSS has been reported.”
“Pseudocarcinomatous hyperplasia is a reactive epidermal hyperplasia characterized by elongated, thickened, and broad rete ridges. It is generally associated with infection (especially deep fungal infection), chronic inflammation, hypersensitivity reactions, and malignancy. Histologically, PEH may closely resemble SCC, especially in biopsy specimens with insufficient dermis. However, unlike SCC, the pathology of pSS lacks nuclear atypia, abundant or abnormal mitoses, and prominent dyskeratosis. Clinicopathological correlation is important in differentiaPEH from SCC.”
