Table 1 Showing TNMB staging of MF

T1: Limited patches, papules, and plaques covering 80% of body surface area

T2: Patches, papules, or plaques covering ≥ 10% of the skin surface. May further stratify into T2a (patch only) vs. T2b (plaque/patch)

T3: One or more tumors (≥ 1-cm diameter)

T4: Confluence of erythema covering > 80% body surface area

N0: No clinically abnormal peripheral lymph nodes; biopsy not required

N1: Clinically abnormal peripheral lymph nodes; histopathology Dutch grade 1 or NCI LN0–2 (N1a, clone negative; N1b, clone positive)

N2: Clinically abnormal peripheral lymph nodes; histopathology Dutch grade 2 or NCI LN3

N3: Clinically abnormal peripheral lymph nodes; histopathology Dutch grades 3 or 4 or NCI LN4; clone positive or negative

NX: Clinically abnormal peripheral lymph nodes; no histologic confirmation

B0: Absence of significant blood involvement: < 5% of peripheral blood lymphocytes are atypical (Sézary) cells

B1: Low blood tumor burden: > 5% of peripheral blood lymphocytes are atypical (Sézary) cells but do not meet B2 criteria

B2: High blood tumor burden: ≥ 1000/mL Sézary cells with positive clone

M0: No visceral organ involvement

M1: Visceral involvement (must have pathology confirmation, and the organ involved should be specified)

IA: T1 N0 M0 B0–1

IIIA: T4 N0–2 M0 B0

IB: T2 N0 M0 B0–1

IIIB: T4 N0–2 M0 B1

IIA: T1–2 N1–2 M0 B0

IVA1: T1–4 N0–2 M0 B0–2

IIB: T3 N0–2 M0 B0–1

IVA2: T1–4 N3 M0 B0–2

IVB: T1–4 N0–3 M1 B0–2