Thyroid Lymphoma Workup

Updated: Jan 18, 2017
  • Author: Fernando Cabanillas, MD; Chief Editor: Emmanuel C Besa, MD  more...
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Workup

Approach Considerations

The diagnosis of thyroid non-Hodgkin lymphoma (NHL) is established by histologic examination of a tumor sample. Laboratory and imaging studies are conducted to establish the stage and prognosis. Thyroid function must also be assessed.

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Laboratory Studies

Once the diagnosis of thyroid non-Hodgkin lymphoma (NHL) is established, the following laboratory studies should be obtained:

  • Complete blood count (CBC)

  • Serum lactate dehydrogenase (LDH) level

  • Serum beta2-microglobulin level

  • Bone marrow aspiration and biopsy

  • Thyroid function tests

  • Antithyroglobulin or antimicrosomal antibodies

The serum LDH and beta2 -microglobulin levels are important because of their ability to help predict the prognosis. [11] The CBC and the bone marrow studies are important as part of the staging evaluation. Because of the high incidence of hypothyroidism, it is important to evaluate thyroid function.

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Plain Radiography, CT, Gallium Scanning, and PET

It is necessary to perform chest radiography and computed tomography (CT) of the head and neck, the chest, the abdomen, and the pelvis. (See the image below.) These are critical tests for determining the stage or extent of disease.

Rapidly enlarging thyroid mass occurring in associ Rapidly enlarging thyroid mass occurring in association with neck adenopathy.

In cases involving bulky disease, either gallium scanning or positron emission tomography (PET) should be performed. These modalities can be helpful later on in determining whether any residual abnormality seen on radiographic studies after treatment contains active lymphoma or just scar tissue.

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Histologic Findings

In current practice, the diagnosis of thyroid lymphoma can be easily established by means of either fine-needle aspiration (FNA) or core-needle biopsy, [11] thus obviating the extensive surgery usually performed for thyroid carcinoma. With the aid of immunophenotyping, non-Hodgkin lymphoma (NHL) should be readily distinguishable from thyroid carcinoma. Furthermore, the distinction between large-cell lymphoma and follicular center-cell lymphoma can be made on the basis of cytologic and immunophenotyping criteria.

The major histologic types of thyroid NHL are as follows [12] :

  • Large-cell lymphoma

  • Follicular lymphoma

  • Mucosa-associated lymphoid tissue (MALT) lymphoma (MALToma)

  • Burkitt lymphoma (rare)

In a study from Japan that evaluated 171 patients with primary thyroid lymphoma, the distribution of pathologic diagnoses was as follows [13] :

  • Diffuse large B-cell lymphoma (DLBCL) - 43%

  • DLBCL with MALToma - 8%

  • MALToma - 47%

  • Other - 2%

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Staging

Determining the extent of disease in NHL is crucial for helping determine the prognosis and select treatment. In thyroid lymphoma, however, a conceptual problem arises, in that most investigators have tended to believe that only thyroid lymphomas that are in the early Ann Arbor stages (ie, I-II) can be considered as being of primary thyroid origin.

The explanation for this view is that advanced presentations can represent a lymphoma metastasizing to the thyroid rather than a primary thyroid lymphoma. Although primary thyroid lymphomas have metastatic potential and can present in stages III-IV, there is no histologic marker that can be used to separate those that are primary in the thyroid from those that are metastatic to the thyroid; thus, most literature series, by definition, include only stage I-II cases.

For the purposes of prognosis, the aggressive thyroid cell types (most commonly the large-cell NHLs) can be classified on the basis of the International Prognostic Index (IPI). [14] This prognostic system assigns 1 point to each of the following variables:

  • Age older than 60 years

  • Performance status greater than 1

  • Elevated lactic dehydrogenase (LDH) level

  • Number of extranodal sites greater than 1

  • Ann Arbor stage III-IV

In a study by Ha et al that tested the ability of the IPI to predict the prognosis for patients with thyroid lymphoma, the 5-year survival rate was 86% for those presenting with an IPI of 0, compared with 50% for those with an IPI greater than 0. [12] . These data included patients treated with radiation therapy alone, patients treated with chemotherapy alone, and patients treated with combined-modality therapy. A 2010 study evaluated prognostic factors in a large population-based study and found that older age, advanced stage, histologic subtype, and lack of radiation/surgical treatment were adverse factors for survival. [9]

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