Protected: CD8+ Hypopigmented Mycosis Fungoides

Case Overview

By Dr. Vickers, Sagis Diagnostics
Educational dermpath case series for dermatology residents

Patient: 17-year-old male
Lesion Location: Diffuse hypopigmented patches across the body

---

This biopsy is from a 17-year-old male patient with white patches present for 2 years at the time of biopsy. Take a moment to review the clinical and histologic images below, do you know how Dr. Vickers came to this diagnosis?

(Image 1: Clinical photo — hypopigmented patches on patient’s skin)

 

(Image 2: High power showing atypical lymphocytes with perinuclear halos)

 

Key Histologic Findings

On examination, several defining features stand out:

• Aggregates of atypical lymphocytes
• Epidermotropism — migration of lymphocytes from the dermis into the epidermis
• “Halos” — perinuclear clearing around individual intraepidermal lymphocytes
• CD8+ T-cell predominance (in contrast to the typical CD4+ phenotype of conventional MF)
• Melanocyte damage by CD8+ cytotoxic lymphocytes, producing clinical hypopigmentation

 

(Image 3: IHC CD3 – Medium power showing epidermotropism)

(Image 4: CD4)

(Image 5: IHC CD8)

 

Differential Diagnosis: Three Common Mimickers

When evaluating hypopigmented patches in a young patient, several differentials come to mind. Let’s walk through the three most likely contenders and highlight what sets them apart.

 

1️⃣ Lichen Planus

Etiology: T-cell mediated lichenoid interface dermatitis; may be idiopathic, drug-induced, or autoimmune

Histology:

• Dense band-like lymphocytic infiltrate at the dermoepidermal junction
• Saw-tooth rete ridges with irregular epidermal hyperplasia
• Civatte bodies (necrotic keratinocytes at the DEJ)
• Max-Joseph spaces (subepidermal clefting) may be present
• Lymphocytes are mature and non-atypical; no halo-forming epidermotropism

 

Key Distinction: Lichen planus produces a band-like infiltrate at the DEJ with Civatte bodies, but the lymphocytes are mature and polyclonal. CD8+ MF displays nuclear irregularity and epidermotropism with halos — features absent in LP. Immunostains demonstrating a clonal CD8+ T-cell population and TCR gene rearrangement studies confirm MF.

(Image 6: Lichen planus — band-like infiltrate and saw-tooth rete ridges for comparison)

 

2️⃣ Eczema (Spongiotic Dermatitis)

Etiology: Epidermal barrier dysfunction with type 2 immune hypersensitivity; often atopic in origin

Histology:

• Spongiosis — intercellular edema within the epidermis
• Vesicle formation in acute cases
• Superficial perivascular lymphocytic infiltrate with eosinophils
• Lymphocytes are small, mature, and non-atypical
• No discrete halo-forming epidermotropism

 

Key Distinction: Eczema and CD8+ MF can appear deceptively similar at low power, both showing a superficial lymphocytic infiltrate. However, spongiotic dermatitis features spongiosis and lacks the atypical lymphocytes and halo-forming epidermotropism of MF. The absence of T-cell clonality on TCR gene rearrangement studies further supports eczema over MF.

 

3️⃣ Drug Eruption

Etiology: Type IV delayed hypersensitivity reaction to a systemically administered medication

Histology:

• Superficial and/or deep perivascular infiltrate of lymphocytes and eosinophils
• Interface changes possible, including vacuolar alteration
• Eosinophils are a helpful clue — often prominent
• Lymphocytes are mature and reactive, not atypical
• Clinically resolves after drug cessation — unlike MF

 

Key Distinction: Drug eruptions may show interface changes superficially overlapping with patch-stage MF, but the lymphocytes are reactive rather than clonal. Prominent eosinophils and a temporal relationship with a medication favor drug eruption. Drug eruptions resolve with drug withdrawal; CD8+ MF is a T-cell lymphoma requiring ongoing management.

 

The Final Diagnosis:

CD8+ Hypopigmented Mycosis Fungoides

The presence of epidermotropism, atypical lymphocytes with perinuclear halos, and a dominant CD8+ T-cell immunophenotype is diagnostic. This variant is not associated with the typical CD4+ phenotype, setting it apart from conventional MF. Correct identification matters: these patients are often young, and an accurate diagnosis directs appropriate therapy while sparing unnecessary workup for other conditions.

 

Key Takeaways for Residents:

 

• Always consider MF in a young patient with persistent hypopigmented patches unresponsive to standard therapy — biopsy early.
• Epidermotropism with halos is the key histologic clue: atypical lymphocytes in the epidermis surrounded by a clear perinuclear space.
• Order immunostains — a CD3+/CD8+ dominant T-cell infiltrate with variable loss of CD5 or CD7 is characteristic.
• Confirm clonality — TCR gene rearrangement studies are essential when histology is equivocal.
• Reassure the patient and family — this variant often follows an indolent course and may respond well to phototherapy (NB-UVB or PUVA).

 

📚 Quick Summary

Feature	CD8+ Hypo MF	Lichen Planus	Eczema	Drug Eruption
Patient profile	Kids, teens, melanated skin	Any age	Any age, atopic	Any age
Atypical lymphocytes	✅ Present	❌ Absent	❌ Absent	❌ Absent
Epidermotropism w/ halos	✅ Present	❌ Absent	❌ Absent	❌ Absent
Eosinophils	❌ Absent	❌ Rare	✅ Possible	✅ Common
Spongiosis	❌ Absent	❌ Absent	✅ Present	✅ Possible
CD8+ phenotype	✅ Dominant	❌ Mixed	❌ Mixed	❌ Mixed
T-cell clonality	✅ Yes	❌ No	❌ No	❌ No
Hypopigmentation	✅ Characteristic	❌ Not typical	❌ Not typical	❌ Not typical
Behavior	Indolent MF	Benign / chronic	Benign / chronic	Resolves w/ drug removal

 

💬 Final Thought

CD8+ Hypopigmented Mycosis Fungoides is a classic dermatopathology “look-alike” that rewards careful microscopic examination. Remember: the “halos” tell the story.

 

Sagis Diagnostics is proud to support dermatology residents and dermatology residency programs through high-quality educational content and histopathologic learning resources.

Follow us on Instagram for more micro-learning opportunities with interactive cases and pathology insights.