Cryptorchidism (from the Greek kruptos, hidden, and orkhis, testicle) is a term describing incomplete testicular descent. Normally, the testis descends into the pelvis by the third month of gestation, and then through the inguinal canal into the scrotum during the last two months of gestation.  (more…)
Q. What is the connection between dysplasia and neoplasia? I understand that dysplasia is a precancerous condition. Grades I and II are not neoplastic. But grade III dysplasia, also called carcinoma in situ, is neoplastic, right? But is it a true carcinoma, or is it not at that point malignant?
A. Dysplasia is not a neoplastic process. While it is often a precursor to neoplasia, not all cases will evolve into malignancy (e.g., mild cervical dysplasia usually does not progress to carcinoma. We watch patients who have it carefully, though, to catch those patients that do go down that path.).
Carcinoma in situ is neoplastic. The cells in carcinoma in situ have the potential to invade (and definitely will, if left alone and untreated). They have acquired enough genetic mutations to have the characteristics of malignant cells (they are able to invade, able to grow on their own without growth signals, insensitive to growth-inhibiting signals, able to metastasize, etc).
Some classification schemes equate grade III dysplasia with carcinoma in situ, while others leave carcinoma in situ in its own category at the far end of the nastiness spectrum. Personally, I prefer the latter way of looking at things, because keeps the separation between dysplasia and neoplasia intact.
The important thing to remember, no matter what semantics you choose, is that the chances of evolution into overt carcinoma rise with the degree of dysplasia. Mild dysplasia usually does not evolve into carcinoma, whereas severe dysplasia usually does.
The image above shows a portion of cervical epithelium that has undergone dysplastic change. The right hand side of the image shows normal squamous epithelium, and the left hand side of the image shows moderately dysplastic epithelium. The dysplastic epithelial cells are pleomorphic (varying in size and shape) and hyperchromatic (darkly-staining) nuclei. Their architecture is also disrupted. Instead of the nice basal layer and orderly maturation and flattening-out of cells that you see in normal epithelium, much of the epithelial thickness resembles the basal layer.
I thought we’d do something a little different today. Take out your pencils and paper, please, we’re going to have a quiz. (more…)
Q. What is the difference between a thyroid nodule, a multinodular goiter and a toxic multinodular goiter?
A. Great question! Let’s look at each separately.
A thyroid nodule is simply what it sounds like: a lump in the thyroid, usually one that’s felt by the patient or the clinician. The term “thyroid nodule” doesn’t indicate anything about the underlying pathology, it is simply a clinical, descriptive term.
Lumps or nodules in the thyroid can be caused by many different things, including both non-neoplastic disorders (multinodular goiter, thyroiditis, Graves disease), and neoplasms (adenoma and carcinoma). Non-neoplastic disorders are the most common cause, followed by adenoma, and then carcinoma.
So nodules should always be investigated because of the possibility (though small) of carcinoma.
A multinodular goiter is simply a goiter that’s been around for a while and has had a chance to grow and become lumpy. “Goiter” simply means “enlarged thyroid” – so technically, you can use the term goiter to refer to any big thyroid.
But when you put the term multinodular in front of goiter, it usually means that the goiter is caused by an inability to produce thyroid hormone at a normal rate. There are lots of reasons a patient may be unable to make thyroid hormone.
In underdeveloped countries multinodular goiters most commonly are a result of iodine deficiency. This really bugs me, because how hard would it be to just give people in these areas iodinized salt? Not hard at all. So why don’t we do this?
In this country, iodine deficiency is rare (check out the photo above of iodinized salt), and the reasons for decreased thyroid hormone production are often unclear.
Either way, a low T4 level causes the pituitary to secrete more TSH, which makes the thyroid grow bigger (hence, the goiter). As this process evolves, some areas of the thyroid are growing and trying to produce thyroid hormone and others are not growing, but involuting. Repeated cycles of growth and involution can damage the thyroid, and as it repairs itself, fibrosis occurs, leading to a lumpy-bumpy, multinodular goiter.
“Toxic” means that the thyroid is producing thyroid hormone at a greatly increased rate. The term “toxic multinodular goiter” is loosely used to describe any lumpy thyroid that is producing excess thyroid hormone.
This could occur in a thyroid adenoma that’s producing thyroid hormone (and which appears clinically as a lump) or it could occur within the context of a true multinodular goiter (caused by the inability to make thyroid hormone).
Sometimes, for reasons that are not clear, a nodule within a multinodular goiter can sort of break away and start producing thyroid hormone autonomously (without the input of TSH). In these instances, the patient may actually become hyperthyroid!
Note: the cool vintage Morton Salt ad belongs to jbcurio, and can be found at: http://w.com/photos/jbcurio/2173554959/.
The final member of the thyroiditis quartet is lymphocytic thyroiditis (also called silent thyroiditis). This type of thyroiditis is characterized histologically by – you guessed it – a ton of lymphocytes (as in the image above). (more…)
Thyroiditis means inflammation of the thyroid gland. You probably already know this, but just to be thorough: the suffix “itis” means inflammation. So appendicitis = inflammation of the appendix, meningitis = inflammation of the meninges, dermatitis = inflammation of the skin, etc.
There are four kinds of thyroiditis: Hashimoto, subacute granulomatous, lymphocytic, and fibrosing. (more…)
We talked a bit about thyroiditis yesterday. Here’s another kind of thyroiditis: fibrosing (or Riedel) thyroiditis. (more…)
“Thyroiditis” means “inflammation of the thyroid gland” (any time you see “-itis,” think “inflammation”). (more…)
There are four types of thyroid carcinoma: papillary, follicular, medullary, and anaplastic carcinoma. (more…)
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