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General facts of thymus cancer

The thymus is a small organ located in the upper/front portion of your chest, extending fromthe base of the throat to the front of the heart. The thymus is composed of an inner medullaand an outer cortex, and is surrounded by a thin covering called the capsule. The thymusreaches its maximum weight of about 1 ounce during puberty, then slowly decreases in sizeduring adulthood and is gradually replaced by fat tissue.During fetal development and childhood, the thymus is involved in the production andmaturation of T-lymphocytes, a type of white blood cell important in the immune system. T-lymphocytes develop in the thymus and then travel to lymph nodes (bean-sized collections of immune system cells) throughout the body. There they help the immune system protect thebody from viruses, fungus, and other types of infections.

A934: thymus : thymoma

The thymus contains 2 main types of cells, thymic epithelial cells and lymphocytes. Thymicepithelial cells can give origin to thymomas and thymic carcinomas. Lymphocytes, whether inthe thymus or in the lymph nodes, can become malignant and develop into cancers calledHodgkin disease and non-Hodgkin lymphomas. More Information about these cancers isavailable in additional documents from the American Cancer Society.

The thymus also contains another much less common type of cells called Kulchitsky cells, orneuroendocrine cells, which normally release certain hormones. These cells can give rise to

cancers, called carcinoids or carcinoid tumors that often release the same type of hormones,and are similar to other tumors arising from neuroendocrine cells elsewhere in the body.

Thymomas, thymic carcinomas, and thymic carcinoid tumors can be distinguished from oneanother and from other tumors of the thymus (such as Hodgkin disease and non-Hodgkinlymphoma) by their appearance under the microscope and results of other laboratory testsperformed on tissue samples.

Doctors disagree about the best way to describe and classify thymomas. In the past,thymomas were sometimes divided into benign thymomas (not cancerous) and malignantthymomas (considered cancerous because of evidence they had invaded or penetratedbeyond the thymus into other tissues or organs). The view currently held by most doctors isthat all thymomas are potentially cancerous, and the best way to predict their prognosis (theoutlook for chances of survival) is to describe whether they have invaded beyond the thymusand, if so, how far. Extent of invasion is identified by the surgeon who notes whether or notthe tumor appears attached to nearby organs, and by the pathologist who looks at samplesfrom the margins (edges) of the tumor under the microscope, to see whether thymoma cellshave spread among cells from othertissues or organs.

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Thymomas are classified by a system recently developed by the World Health Organization(WHO). This system assigns a letter grade to the thymomas based on their appearance underthe microscope. These are:

Type A: The cells are spindle-shaped or oval and do not appear very malignant. Around 5%of thymomas are this type. The outlook for people with this kind of thymoma is quite goodand most are cured.

Type AB: This type looks like type A except in addition there are lymphocytes mixed in thetumor. Nearly 1/3 of thymomas are this type. The outlook for people with this type is alsoquite good. Most people are cured.

Type B1: This type is recognized because it has a lot of lymphocytes, the cells responsiblefor immunity along with normal-appearing thymus cells. It has a very good outlook. About90% of people with this type are cured. About 10% to 20% are this type.

Type B2: This type also has a lot of lymphocytes, but the thymus cells do not appearnormal. Instead, they are larger with abnormal nuclei (the DNA-containing part of the cell).This has a less favorable outlook, with about 60% of patients cured. About 20% to 35% arethis type.

Type B3: This type has few lymphocytes and mostly consists of thymus cells that look prettyclose to normal. The outlook for this type is somewhat less favorable than for B2 thymomas,with only about 40%of patients cured. About 10% to 15% of thymomas are this type.

Type C: This is also known as thymic carcinoma and is the most aggressive kind of thymustumor. It has a very different appearance from normal thymus tissue. Thymic carcinomas areformed by cells that have certain abnormalities that are clearly recognized under themicroscope. These cells usually invade nearby tissues and can often metastasize (spread todistant tissues and organs).

Thymic carcinomas are further divided into low-grade (better prognosis) and high-grade(worse prognosis, that is, more likely to grow and spread quickly) categories. Around 25% of people with thymic carcinoma are cured.

Low-grade thymic carcinomas include well-differentiated squamous cell, mucoepidermoid,and basaloid types.High-grade thymic carcinomas include poorly differentiated squamous cell,small cell/neuroendocrine, clear cell, anaplastic/undifferentiated, and sarcomatoid types.

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A934: thymus: thymomaLot. No : 120212083021

T1 T2 N1

RNA conc.(ng/ul)

118.68 442.18 18.16

260/280 1.94 1.86 1.88

AGE: 73Sex: MaleStage: thyroma

Pathology:

* Comment: alcohol, smoking, family history: mother cancer death

1.Thymus, thymectomy:Mixed cortical and medullary thymoma(by Muller-Hermelink classification)1) Type AB, by WHO classification.2) Confined within the capsule, but vascular permeation positive.

Fig3. RT-PCR forGAP3DHSample : Serial 10sections of 10micrometer slice

Fig 1. Scanned images for H&Estained slides.

Pathology or other information:

N1T1 T2

N1T1 T2