A 58-year-old Indian male presents with a 5-year history of pruritic erythematous scaly patches on his buttocks, lower abdomen, and medial thighs that have been misdiagnosed as eczema. Skin biopsy reveals atypical cerebriform lymphocytes with epidermotropism and Pautrier microabscesses; immunophenotype shows CD3+ CD4+ CD8− CD45RO+ cells with loss of CD7. The distribution pattern shown as **A** in the diagram is characteristic of which stage of mycosis fungoides?

Question

Accepted Answer

D. Stage IA-IB (patch stage). ## Why Stage IA-IB (patch stage) is right

The bathing-suit distribution pattern shown as **A** — erythematous scaly patches in sun-protected areas (buttocks, breasts, hips, lower abdomen, medial thighs) — is the hallmark of early mycosis fungoides and corresponds to TNMB stage IA-IB (patch stage). This represents the earliest clinical manifestation of the disease, often misdiagnosed as eczema or psoriasis for 4–6 years before correct diagnosis. The histopathology (atypical cerebriform lymphocytes, epidermotropism, Pautrier microabscesses) and immunophenotype (CD3+ CD4+ CD8− CD45RO+ with CD7 loss) confirm CTCL. Stage IA-IB has excellent prognosis (>95% 5-year survival) and is managed with skin-directed therapy (topical corticosteroids, nitrogen mustard, PUVA, NBUVB).

## Why each distractor is wrong

- **Stage IIA (plaque stage)**: Plaque stage is characterized by infiltrated, indurated plaques rather than patches. While the distribution may remain similar, the clinical morphology has progressed beyond the flat, scaly patch appearance shown in **A**.
- **Stage IIB (tumor stage)**: Tumor stage involves nodules or tumors ≥1 cm with frequent ulceration. The lesions in **A** are described as patches, not nodular or ulcerated tumors.
- **Stage III (erythrodermic MF/Sezary syndrome)**: Erythrodermic MF presents with diffuse erythroderma covering >80% of body surface area, often with lymphadenopathy and circulating atypical T-cells. The localized bathing-suit distribution in **A** does not meet criteria for erythroderma.

**High-Yield:** Bathing-suit distribution (buttocks, breasts, hips, lower abdomen, medial thighs) = early patch-stage mycosis fungoides; median 4–6 years to diagnosis due to mimicry of eczema/psoriasis.

[cite: Bolognia Dermatology 5e Ch 120; WHO-EORTC CTCL classification 2018; ISCL/EORTC 2007 TNMB staging]

Answer

A. Stage IIB (tumor stage)

Answer

B. Stage IIA (plaque stage)

Answer

C. Stage III (erythrodermic MF/Sezary syndrome)

Explanation

Why Stage IA-IB (patch stage) is right

Why each distractor is wrong

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