CD30 positive T cell lymphoproliferative disorder

by Jason Wasserman MD PhD FRCPC and Aleksandra Paliga MD FRCPC
December 18, 2024

This article will help you understand your pathology report for CD30 positive T cell lymphoproliferative disorder. Each section explains an important aspect of the diagnosis and what it means for you.

What is primary cutaneous CD30 positive T cell lymphoproliferative disorder?

Primary cutaneous CD30 positive T cell lymphoproliferative disorder describes a group of immune system cancers involving T cells that express a protein called CD30. These cancers primarily affect the skin and are part of a spectrum of related conditions. This group includes both indolent (slow-growing) and more aggressive diseases. Additional tests are usually performed to refine the diagnosis further.

What cancers are included in primary cutaneous CD30 positive T cell lymphoproliferative disorder?

Several types of T cell cancers express CD30 and are part of this spectrum. These include:

• Lymphomatoid papulosis: A chronic condition characterized by small, raised skin lesions that often heal on their own but can recur. Despite being cancerous, it behaves relatively indolently and rarely progresses.
• Primary cutaneous anaplastic large cell lymphoma: A localized cancer that typically presents as larger tumours in the skin, often red or purple in colour. These tumours may ulcerate and cause discomfort. The disease usually remains confined to the skin, although it can spread in rare cases.
• CD30-positive advanced mycosis fungoides: A type of lymphoma in the skin where the cancer cells express CD30. Unlike other conditions in this group, mycosis fungoides often starts as patchy, scaly skin lesions that evolve into thicker plaques or tumours in advanced stages. CD30 expression may develop as the disease progresses.
• Overlap cases: Some cases show a mix of features from lymphomatoid papulosis and primary cutaneous anaplastic large cell lymphoma, making diagnosis more challenging.

Each condition has different behaviours and treatment approaches, so pathologists must determine which is present.

How do pathologists distinguish between these types of CD30 positive skin cancer?

Pathologists examine tissue samples under a microscope to determine the size, shape, and arrangement of cancer cells. This helps them differentiate between different types of CD30 positive T cell lymphoproliferative disorders.

Microscopic features

• Lymphomatoid papulosis: The cancer cells are scattered throughout the skin and mixed with normal immune cells, such as histiocytes, eosinophils, and neutrophils. This creates an inflammatory background. The cancer cells are often small to medium-sized with irregular shapes, and their scattered appearance gives the lesions a less dense, patchy look.
• Primary cutaneous anaplastic large cell lymphoma: The cancer cells are larger and form dense clusters or sheets within the skin. These cells have irregularly shaped nuclei (the part of the cell containing genetic material), prominent nucleoli (small structures inside the nucleus), and abundant cytoplasm (the substance surrounding the nucleus). The tumours may also show areas of ulceration, with some inflammation caused by the immune system’s response.
• CD30-positive advanced mycosis fungoides: The cancer cells in mycosis fungoides are usually smaller than those in primary cutaneous anaplastic large cell lymphoma. They infiltrate the skin in bands or clusters and may form plaques or tumours in advanced stages. The cells tend to have a cerebriform (brain-like) appearance due to their irregularly folded nuclei. CD30 expression often appears in advanced stages, especially in tumours.
• Peripheral anaplastic large cell lymphoma involving the skin: This type of cancer shares many microscopic features with primary cutaneous anaplastic large cell lymphoma, including large, irregularly shaped cells strongly expressing CD30. However, pathologists look for signs that the cancer started outside the skin, such as evidence of spread to internal organs or lymph nodes. Additional tests, such as imaging or blood tests, help determine the origin of the disease.

Additional tests

Pathologists often use one or more additional tests to help further refine the diagnosis. These test include:

• Immunohistochemistry: This test highlights specific proteins like CD30 on the cancer cells. Other markers, such as CD4 and CD8, may also be tested to understand the type of T cell involved.
• Fluorescence in situ hybridization (FISH): FISH looks for genetic rearrangements, such as changes in the DUSP22 locus, which can help classify the cancer.
• Next-generation sequencing (NGS): NGS examines multiple genes to identify mutations or other changes that might influence treatment options.
• Polymerase chain reaction (PCR): PCR looks for specific genetic changes, providing additional details about the cancer’s origin and behaviour.

These tests help pathologists identify the type of CD30 positive T cell disorder and guide treatment decisions.

Why is it important to distinguish between these types of cancer?

The CD30 positive T cell lymphoproliferative disorder type determines the prognosis and best treatment. For example:

• Lymphomatoid papulosis often resolves on its own or requires minimal treatment.
• Primary cutaneous anaplastic large cell lymphoma may need localized treatments, such as surgery or radiation, or systemic therapy if the disease is widespread.
• Identifying genetic changes, like DUSP22 rearrangements, can provide additional information about how the disease may behave.