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- Presentation
A Dermatopathology Journey from Viral Rashes to ALK-Positive Skin Tumors
Description
The talk presented several dermatopathology cases that moved from rashes to tumors. It began with a young woman with a rapidly spreading vesicular rash initially suggestive of herpes because of reticular degeneration on biopsy, but HSV stains and viral PCR were negative; with fever, fatigue, and positive rhino-enterovirus testing, the case was diagnosed as hand, foot, and mouth disease, noted as often atypical in adults and capable of mimicking varicella or eczema herpeticum. The speaker then reviewed other causes of reticular degeneration, including ORF, smallpox, and monkeypox, emphasizing their characteristic histology and clinical contexts. The second half focused on a 41-year-old man with a pedunculated purple papule on the forearm whose biopsy showed plump epithelioid, binucleate cells with collarette, and ALK positivity, leading to a diagnosis of epithelioid fibrous histiocytoma. The speaker highlighted its distinguishing molecular ALK rearrangements, histologic features, spindle-cell and myxoid variants, and the importance of choosing the right ALK antibody clone for immunostaining.
View moreConclusions
- The presentation concludes that hand, foot, and mouth disease can present with reticular degeneration on biopsy and may be atypical in adults, making it an important herpes and varicella mimic to recognize.
- It suggests that identifying atypical HFMD is clinically useful because it can prevent unnecessary testing, treatment, and transmission while improving diagnosis.
- The talk concludes that reticular degeneration has a broad differential that includes poxviruses such as orf, smallpox, and monkeypox, along with nutritional deficiency, erythema multiforme, fixed drug eruption, and hydroa vacciniforme.
- It emphasizes that monkeypox can show histologic reticular degeneration and that current outbreaks may present with genital lesions that mimic sexually transmitted infections.
- The mass case supports that epithelioid fibrous histiocytoma is a distinct ALK-rearranged entity rather than simply a dermatofibroma variant.
- It concludes that epithelioid fibrous histiocytoma typically presents as a circumscribed polypoid or dome-shaped lesion with epithelioid, often binucleate cells and a characteristic collarette.
- The presentation also concludes that spindle cell and myxoid variants of epithelioid fibrous histiocytoma exist, so the diagnosis can be more varied than the classic form.
- It warns that ALK immunostaining is clone-dependent, and the D5F3 clone is more sensitive than ALK1 for detecting these lesions.
- Lipe et al. “Atypical Presentation of Hand, Foot, and Mouth Disease in an Adult.”#10.5811/cpcem.2018.3.37686
- D5F3 Clone
- ALK1 Clone