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PubMed This is a summary of 15 peer-reviewed journal articles Updated
Oncology

Staging and Pathology: What TNMB Means for You

At a Glance

The TNMB staging system for primary cutaneous lymphoma evaluates Tumor (skin involvement), Nodes, Metastasis, and Blood. Your pathology report also identifies specific cell markers and confirms cell clonality, which determines your exact lymphoma subtype and guides targeted treatments.

Deciphering a pathology report can feel like learning a new language. For primary cutaneous lymphoma (PCL), this language is highly specialized. Unlike many other cancers that use the “Ann Arbor” staging system (designed for internal lymph nodes), skin lymphomas use the TNMB system to account for the unique way these diseases live in the skin and blood [1][2].

The TNMB Staging System

For Mycosis Fungoides and Sézary Syndrome, doctors use four specific categories to determine your stage [2]:

  • T (Tumor/Skin): This measures how much of your skin is affected. T1 means less than 10% of your body surface is covered (about the size of 10 of your palms); T2 is 10% or more; T3 means you have one or more tumors; and T4 is erythroderma, where nearly the entire body is red and scaly [2][3].
  • N (Nodes): This tracks whether the lymphoma has moved into the lymph nodes. N0 means no involvement, while higher numbers indicate abnormal cells found in a node biopsy [4].
  • M (Metastasis): This tracks if the disease has spread to internal organs like the liver or lungs. This is rare in early-stage PCL [1].
  • B (Blood): This is unique to skin lymphoma. Using a test called flow cytometry, doctors count how many “atypical” cells are in your bloodstream. B0 is little to no involvement; B2 indicates a high number of cells and is a hallmark of Sézary Syndrome [5][6].

Pathology Checklist: Key Markers

Your pathology report is a map of the proteins found on your cancer cells. These “markers” tell your doctor which subtype you have and which treatments will work best [1].

Marker/Test What it Means Why it Matters
Clonality (PCR) Confirms that the cells are “clones” of each other [7]. Helps distinguish lymphoma from normal inflammation like eczema or psoriasis [8].
CD30 A protein found on the surface of some T-cells [9]. If positive, it can be targeted by a highly effective “smart bomb” drug called brentuximab vedotin [10].
CD20 A marker found on B-cells [11]. Confirms a Cutaneous B-Cell Lymphoma (CBCL) diagnosis and makes you a candidate for targeted B-cell therapies like rituximab [12].
BCL2 & MUM1 Proteins often seen in B-cells [12]. High levels of these can help identify more aggressive types, like Leg Type B-cell lymphoma [13].
Flow Cytometry A laser-based blood test [14]. Essential for identifying “Blood” involvement (B stage) and confirming the diagnosis of Sézary Syndrome [15].

Understanding “Clonality”

One word you will see often is clonality. In a healthy person, the immune cells in a rash are diverse—they are different “families” of cells fighting a trigger. In lymphoma, the cells are clonal, meaning they are all identical copies of one original malignant cell [7]. Identifying a “clone” through a T-cell receptor (TCR) or B-cell receptor (BCR) gene rearrangement test is often the final piece of the puzzle that confirms the diagnosis [8].

Staging for B-Cell Lymphomas (CBCL)

Staging for B-cell types is slightly different. Instead of focusing on body surface area percentages, it focuses on whether the lesions are solitary (one spot), regional (several spots in one area), or multifocal (spots in multiple different areas of the body) [1]. Because most B-cell types stay in the skin, “B” (blood) staging is rarely used for these patients [1].

Return to Home

Common questions in this guide

What does the TNMB staging system mean for skin lymphoma?
TNMB stands for Tumor, Nodes, Metastasis, and Blood. Unlike systems for other cancers, TNMB specifically measures how much of your skin is affected, lymph node involvement, internal organ spread, and the number of abnormal cells in your bloodstream.
What does clonality mean on my pathology report?
Clonality means that the abnormal immune cells are all identical copies of one original cancer cell. Finding a clone through genetic testing helps doctors confirm a lymphoma diagnosis and distinguish it from normal skin inflammation like eczema or psoriasis.
What does a CD30 positive test result mean?
CD30 is a specific protein found on the surface of some T-cells. If your biopsy is CD30-positive, it means your lymphoma might be successfully treated with a targeted 'smart bomb' medication called brentuximab vedotin.
How do doctors test for blood involvement in Sézary Syndrome?
Blood involvement, known as the 'B' stage, is measured using a laser-based blood test called flow cytometry. This test counts the exact number of atypical cells in your bloodstream to determine if you have a B0, B1, or B2 score, which is critical for diagnosing Sézary Syndrome.
Is staging different for Cutaneous B-Cell Lymphoma (CBCL)?
Instead of measuring the percentage of body surface area covered by a rash, B-cell lymphoma staging focuses on how the spots are grouped. Doctors check if your skin lesions are solitary (one spot), regional (several spots in one area), or multifocal (spread across multiple areas).

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Based on my skin exam, what is the 'T' score in my TNMB stage, and how was my body surface area (BSA) calculated?
  2. 2.What was the 'B' score on my flow cytometry? Does the absolute count of abnormal cells put me in the B0, B1, or B2 category?
  3. 3.Did my biopsy show 'clonality' through T-cell receptor (TCR) or B-cell receptor (BCR) gene rearrangement testing?
  4. 4.What is the percentage of CD30-positive cells in my biopsy, and does this indicate 'Large Cell Transformation'?
  5. 5.For my B-cell diagnosis, did the pathology test for BCL2 and MUM1/IRF4 markers to rule out or confirm 'Leg Type' lymphoma?

Questions For You

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References

References (15)
  1. 1

    Primary cutaneous lymphoma: recommendations for clinical trial design and staging update from the ISCL, USCLC, and EORTC.

    Olsen EA, Whittaker S, Willemze R, et al.

    Blood 2022; (140(5)):419-437 doi:10.1182/blood.2021012057.

    PMID: 34758074
  2. 2

    Management Strategies for Mycosis Fungoides in India.

    Raychaudhury T

    Indian journal of dermatology 2017; (62(2)):137-141 doi:10.4103/ijd.IJD_71_17.

    PMID: 28400632
  3. 3

    Monoclonal antibodies against cutaneous T-cell lymphomas.

    Alaibac M

    Expert opinion on biological therapy 2017; (17(12)):1503-1510 doi:10.1080/14712598.2017.1369951.

    PMID: 28829215
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    Allogeneic haematopoietic cell transplant in cutaneous T-cell lymphomas: Recommendations from the EBMT PH&G Committee.

    Damaj G, de Masson A, Dreger P, et al.

    Journal of the European Academy of Dermatology and Venereology : JEADV 2025; doi:10.1111/jdv.70042.

    PMID: 41031482
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    Blood classification and blood response criteria in mycosis fungoides and Sézary syndrome using flow cytometry: recommendations from the EORTC cutaneous lymphoma task force.

    Scarisbrick JJ, Hodak E, Bagot M, et al.

    European journal of cancer (Oxford, England : 1990) 2018; (93()):47-56 doi:10.1016/j.ejca.2018.01.076.

    PMID: 29477101
  6. 6

    CD4+CD26- lymphocytes are useful to assess blood involvement and define B ratings in cutaneous T cell lymphoma.

    Vonderheid EC, Hou JS

    Leukemia & lymphoma 2018; (59(2)):330-339 doi:10.1080/10428194.2017.1334123.

    PMID: 28595473
  7. 7

    Nanopore Sequencing for T-Cell Receptor Rearrangement Analysis in Cutaneous T-Cell Lymphoma.

    Cieslak C, Hain C, Rückert-Reed C, et al.

    Cancers 2024; (16(21)) doi:10.3390/cancers16213700.

    PMID: 39518138
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    Dupilumab therapy in atopic dermatitis when cutaneous lymphoma is suspected: Consensus recommendations from the EORTC Cutaneous Lymphoma Tumour Group.

    Calvão J, de Masson A, Cozzio A, et al.

    The Journal of allergy and clinical immunology 2026; (157(6)):1237-1245 doi:10.1016/j.jaci.2026.04.002.

    PMID: 41967816
  9. 9

    Primary cutaneous lymphoma in Argentina: a report of a nationwide study of 416 patients.

    Abeldaño A, Enz P, Maskin M, et al.

    International journal of dermatology 2019; (58(4)):449-455 doi:10.1111/ijd.14262.

    PMID: 30294921
  10. 10

    Randomized phase 3 ALCANZA study of brentuximab vedotin vs physician's choice in cutaneous T-cell lymphoma: final data.

    Horwitz SM, Scarisbrick JJ, Dummer R, et al.

    Blood advances 2021; (5(23)):5098-5106 doi:10.1182/bloodadvances.2021004710.

    PMID: 34507350
  11. 11

    Cutaneous B-cell lymphomas: 2023 update on diagnosis, risk-stratification, and management.

    Hristov AC, Tejasvi T, Wilcox RA

    American journal of hematology 2023; (98(8)):1326-1332 doi:10.1002/ajh.26968.

    PMID: 37434388
  12. 12

    Primary Cutaneous B-Cell Lymphomas: An Update.

    Vitiello P, Sica A, Ronchi A, et al.

    Frontiers in oncology 2020; (10()):651 doi:10.3389/fonc.2020.00651.

    PMID: 32528871
  13. 13

    A case of a primary cutaneous diffuse large B-cell lymphoma, leg type.

    Marasca C, Fabbrocini G, Cinelli E, et al.

    International wound journal 2020; (17(2)):514-515 doi:10.1111/iwj.13298.

    PMID: 31884690
  14. 14

    Sézary syndrome and mycosis fungoides: An overview, including the role of immunophenotyping.

    Pulitzer MP, Horna P, Almeida J

    Cytometry. Part B, Clinical cytometry 2021; (100(2)):132-138 doi:10.1002/cyto.b.21888.

    PMID: 32516521
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    The Overlapping Clinicopathological Presentations of Pityriasis Lichenoides and Mycosis Fungoides.

    Pierog O, Estill M, Jedrych J, et al.

    Journal of cutaneous pathology 2025; (52(12)):785-794 doi:10.1111/cup.14856.

    PMID: 40953932

This page explains primary cutaneous lymphoma staging and pathology terminology for educational purposes. Your oncologist and dermatologist are the best sources for interpreting your specific pathology reports.

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