Dupilumab-Associated Sweet Syndrome.

Sweet syndrome (SS), also known as acute febrile neutrophilic dermatosis, is characterized by the abrupt appearance of edematous and erythematous papules, plaques, or nodules on the skin that have a distinct histopathologic appearance. Several subtypes of SS exist, including classic (also referred to as idiopathic) and drug induced. Although multiple medications have been implicated as causative agents, we present a rare case of SS caused by dupilumab, a monoclonal antibody therapy, used in the treatment of severe eosinophilic asthma and other conditions. Clinicians should be aware of this potential adverse reaction, as prompt recognition and treatment are essential.

Differentiation of malignant melanoma from benign nevus using a novel genomic microarray with low specimen requirements.

CONTEXT: Histologic examination of clinically suspicious melanocytic lesions is very sensitive and specific for the detection of malignant melanoma. Yet, the malignant potential of a small percentage of melanocytic lesions remains histologically uncertain. Molecular testing offers the potential to detect the genetic alterations that lead to malignant behavior without overt histologic evidence of malignancy. OBJECTIVE: To differentiate benign melanocytic nevi from malignant melanoma and to predict the clinical course of melanocytic lesions with ambiguous histology using a novel genomic microarray. DESIGN: We applied a newly developed single-nucleotide polymorphism genomic microarray to formalin-fixed, paraffin-embedded melanocytic lesions to differentiate benign nevi (n  =  23) from malignant melanoma (n  =  30) and to predict the clinical course of a set of histologically ambiguous melanocytic lesions (n  =  11). RESULTS: For cases with unambiguous histology, there was excellent sensitivity and specificity for identifying malignant melanoma with this genomic microarray (89% sensitivity, 100% specificity). For cases with ambiguous histology, the performance of this genomic microarray was less impressive. CONCLUSIONS: Without microdissection and with quantities of DNA one-tenth what is required for more commonly used microarrays, this microarray can differentiate between malignant melanoma and benign melanocytic nevi. For histologically ambiguous lesions, longer clinical follow-up is needed to confidently determine the sensitivity and specificity of this microarray. Some of the previous technical hurdles to the clinical application of genomic microarray technology are being overcome, and the advantages over targeted fluorescence in situ hybridization assays currently in clinical use are becoming apparent.

Eosinophils in mycosis fungoides: an uncommon finding in the patch and plaque stages.

Early diagnosis of mycosis fungoides (MF) is one of the most challenging problems in dermatopathology, as the histopathologic features of inflammatory dermatoses and MF may show significant overlap. One criterion used to distinguish early MF (patch stage) from dermatitis, which may be currently underutilized, is the presence of eosinophils. A search was performed for cases with a preoperative diagnosis of MF, cutaneous T-cell lymphoma, or dermatitis, which included 29 cases "diagnostic" for MF, 25 cases "suspicious" for MF, and 55 cases of spongiotic dermatitis. We examined tissue sections blinded to diagnosis to obtain an exact eosinophil count. Twenty-nine cases were diagnostic for MF (12 patch, 9 plaque, and 8 tumor stage). The average eosinophil count for cases diagnostic for patch stage MF was 1 eosinophil in 10 (0.11) sections examined. For plaque MF, there was 1 eosinophil in 5 (0.24) sections examined. All tumor stage MF cases showed abundant eosinophils within each section. Twenty-five cases were suspicious for MF (15 patches, 9 plaques, and 1 folliculotropic). The average eosinophil count for the patch lesions was 1 eosinophil in 4 (0.25) sections examined and 2 eosinophils per section for plaque lesions. Forty-five of 55 cases of spongiotic dermatitis had at least scattered eosinophils (>3) in each section. Twenty-three (47%) had eosinophils around most postcapillary venules. Only 3 of 45 patients (6.6%) with biopsies diagnostic or suspicious for patch or plaque stage MF showed >3 eosinophils per tissue section, whereas 45 of 55 (81.8%) biopsies of spongiotic dermatitis had >3. The presence of eosinophils (>3 per tissue section) is statistically significant in differentiating cases diagnostic or suspicious for patch or plaque stage MF from dermatitis (P < 0.0001). Our data indicate that eosinophils are uncommon in cases of patch and plaque MF. When a pathologist is faced with evaluating a biopsy that lacks some of the criteria used to make the diagnosis of patch stage MF, yet demonstrates >3 eosinophils per tissue section, dermatitis is the likely diagnosis. However, in cases where fewer than 3 eosinophils are present in sections, patch stage MF cannot be excluded.

C4d immunohistochemical stain is a sensitive method to confirm immunoreactant deposition in formalin-fixed paraffin-embedded tissue in bullous pemphigoid.

BACKGROUND: Bullous pemphigoid (BP) is characterized clinically by the onset of pruritic urticarial plaques, vesicles and bullae in a predominantly elderly population. While the diagnosis may be suspected on routine hematoxylin and eosin histology of formalin-fixed paraffin-embedded tissue, fresh-frozen tissue must be used to show the immunologic nature of the bullous process by direct immunofluorescence (DIF). The diagnosis is further confirmed and separated from epidermolysis bullosa acquisita (EBA) by subsequent serologic studies to detect antibodies directed against BP180 and BP230 antigens and characteristic antibody deposition on salt-split skin. METHODS: Using a polyclonal complement fragment 4d (C4d) antibody, we stained formalin-fixed paraffin-embedded skin biopsy specimens from cases of BP and controls. RESULTS: We showed characteristic linear basement membrane deposition of C4d in formalin-fixed paraffin-embedded tissue in seven of nine cases diagnosed as BP vs. EBA by DIF on fresh-frozen tissue. None of the four controls for which we had adequate tissue were positive. CONCLUSION: These results indicate that formalin-fixed paraffin-embedded tissue can be stained for the immunoreactant C4d to show characteristic immunoreactant deposition, potentially obviating the need for repeat biopsy for DIF and allowing clinicians to proceed to serologic confirmation of BP.

Autoimmune acrosyringitis with ductal cysts: reclassification of case of eruptive syringoma.

Syringomas are architecturally complex tumors composed of small, cystically dilated segments of dermal eccrine duct. Syringomas typically form isolated flesh-colored periorbital papules, however, in a peculiar condition termed eruptive syringoma; scores develop simultaneously in near confluence over a large surface area. While traditionally regarded as a neoplasm, more recent observations indicate eruptive syringoma is a reactive proliferation secondary to autoimmune disruption of the acrosyringium. We present the case of a 44-year-old woman with eruptive syringoma of the labia majora and prominent lymphocytic inflammation in the acrosyringium. Immunohistochemical stains confirm that the infiltrate is composed of CD4+ and CD8+ T cells, without significant CD20 B cells or CD138 plasma cells. Sequential sections of the syringoma reveal a complex 3-dimensional architecture with functionally isolated cysts, not connected to adjacent cysts or ducts by a discernable epithelium. These findings support the conclusion that eruptive syringoma is a tortuous proliferation of dermal eccrine ducts and fibrous stroma secondary to autoimmune destruction of the acrosyringium. Conceptually, the disorganized expansion of an eccrine duct syringoma may be analogous to a peripheral nerve traumatic neuroma.