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- Presentation
Diagnostic Delay in Folliculotropic Mycosis Fungoides: A Challenging Case and Lessons Learned
Description
The talk reviewed why diagnosis of cutaneous T-cell lymphoma, especially folliculotropic mycosis fungoides (MF), is often delayed, noting that early-stage disease can be subtle, asymptomatic, hidden under clothing, and frequently mistaken for benign dermatoses. In a prospective international registry, most early-stage patients had diagnostic delay, with a median of 36 months and some delays as long as 90 months. A detailed case was then presented of a 64-year-old man initially treated for presumed psoriasis and later evaluated for persistent nodules, plaques, and follicular lesions that repeatedly yielded nonspecific or misleading biopsy results, including follicular mucinosis, mixed inflammatory infiltrates, granulomatous inflammation, and culture growth suggesting infection. His workup was further complicated by diabetes, immunosuppression, and true or suspected superinfection, which obscured the underlying lymphoma. Only after repeated exams, multiple biopsies over time, and T-cell receptor clonality testing showing matching clones was folliculotropic MF confirmed, after a 14-month delay and seven biopsies. The key lessons were that folliculotropic MF can mimic infection because follicular rupture produces dense mixed inflammation, clonality testing is valuable, and clinicians should obtain multiple biopsies from different morphologies over time—often targeting thinner lesions with follicular prominence rather than the most indurated plaque—while balancing the risk of biopsy fatigue.
View moreConclusions
- Delayed diagnosis is common in MF/CTCL, with prospective data showing a median delay of about 3 years and most early-stage patients experiencing diagnostic delay.
- Diagnostic delay occurs because early MF/CTCL can look like common benign dermatoses, be asymptomatic or hidden, and providers may not biopsy or perform a full skin exam.
- Routine histology can be misleading in early or folliculotropic MF because classic features may be absent and inflammatory patterns can mimic eczema, infection, or granulomatous disease.
- Folliculotropic MF is especially difficult to diagnose because follicular rupture and superinfection can obscure tumor cells and create confusing biopsy results.
- Matching T-cell receptor clonality across multiple biopsies is highly helpful and supports the diagnosis when morphology is equivocal.
- Repeated biopsies from different lesions over time are often necessary, even in specialty centers, because the disease may only become diagnostic later.
- In folliculotropic MF, sampling thinner lesions with less severe follicular prominence may be more informative than biopsying the most indurated areas.
- The presented case shows that a patient initially worked up for psoriasis and infection ultimately had folliculotropic MF, illustrating how red herrings can prolong diagnosis.
- Clinical suspicion should remain high when the skin exam looks classic for MF even if early biopsies suggest infection or benign inflammation.
- The overall message is that patience, repeated clinicopathologic correlation, and serial biopsies are essential because MF/CTCL may not declare itself immediately.
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