24-year-old (male) with ectopic gland tissue

00:03 A 24 year old male undergoes surgery due to a painless swelling in the base of the neck.

00:08 During the operation, a superficial 1.0x0.8 cm mass surrounded by a well-defined fibrous capsule is excised and sent for histological evaluation which reveals this tissue to be an ectopic gland tissue.

00:25 The slide below depicts one of the examined specimens.

00:28 Which gland does this tissue below belong to? Answer choice (A) - thyroid gland Answer choice (B) - parotid gland Answer choice (C) - sublingual gland and answer choice (D) - adrenal gland Now take a moment to come to the answer by yourself before we go through it together.

00:51 Okay, let's jump right in to this question.

00:53 First thing we need to determine is what category of question this is.

00:58 And this is a histology question.

01:00 They're showing us a histological slide so classically, we have to be able to interpret the slide to its histology.

01:07 Now this is a 2-step question.

01:10 The first thing we have to do is be able to interpret what we're looking at here in our histological slide and then be able to answer the specific question which in this case is, 'which gland does this tissue belong to?' And in this case of course, the stem is required.

01:26 It is a complex question, we have to know what they're asking according to this histological image.

01:32 So let's walk through this question together.

01:34 Step 1 in determining this question is, we need to determine what type of tissue we are looking at.

01:41 Now as we can see in our image, the histology slide shows secretory cells arranged in acini and we see the presence of ducts.

01:52 So looking at our image, look at the left side where there is the lighter pink color, we see two circles which are ducts.

01:59 And then you see all these secretory acini close to each other, all these little acini making a circle and if you imagine, we are taking a sagittal cut through the ducts, which is how you are seeing it here on end - these nice little circles.

02:14 And you can see one on the left side, at the 12 o' clock position, also a nice circle of secretory cells arranged in acini which are ducts.

02:23 So here on the left side, we definitely see the presence of two separate ducts.

02:28 Now, really important high-yield point here.

02:31 Endocrine glands DO NOT have ducts.

02:35 An endocrine gland simply secretes directly into the bloodstream.

02:40 So here, we see two ducts and we can say wow, if I'm seeing ducts- not an endocrine gland.

02:46 That really helps me with my finding the right answer.

02:49 And what this tells me is, the tissue I'm looking at here, simply by just looking at the left side of the image right through these two ducts at the 12 o' clock and 9 o' clock positions, that I'm looking at an exocrine gland because exocrine glands have ducts where they release their contents, while endocrine glands do not have ducts and they secrete directly into the bloodstream.

03:11 So that's the first thing I know is, okay I'm looking at an exocrine gland.

03:15 Now step 2- I need to figure out what tissue actually does originate to produce this histology slide .

03:24 Now as we can see, now look at the right side of the image that there's acini and it shows numerous basophilic granules.

03:33 Now this is typical of a serous secretory cells.

03:37 Now if you look at the slide here, we actually don't have any mucus cells.

03:41 So if we look at our answer choices, the first thing we are going to be looking at is an exocrine gland with solely serous cells and that's the parotid gland.

03:51 So the answer choice here is answer choice (B).

03:54 Now let's look at our other ones to figure out why they're wrong.

03:57 well the sublingual gland consists of a mixture of both serous and mucus cells.

04:03 well since we don't see any mucus cells and we're only seeing serous, it cannot be sublingual gland.

04:08 and if we look at our other two answer choices - the thyroid and the adrenal glands, we know that these are both very traditional endocrine glands and they secrete directly into the bloodstream and do not have ducts so it cannot be those either.

04:23 Now a few high yield points regarding both the thyroid and the adrenal glands if they were to show you a histology slide, the thyroid will have follicles with a single layer of either cuboid or low columnar epithelium.

04:36 Those are high-yield points to look for.

04:38 And then the adrenal gland if they wiere to show you the cortex - that's the adrenal component, excuse me that's the actual endocrine component of the adrenal gland, we're gonna be looking for three zones - the glomerulosa, the fasciculata and the reticularis and separately you will see the medulla.

04:54 Now in conclusion for this question, let's think about it.

04:58 The histology slide is showing us ectopic tissue, hence the ducts and we're seeing parotid gland because we only see the serous and no mucus cells.

05:08 So thus the correct answer is answer choice (B) - the parotid gland.

05:13 now let's review some high-yield facts regarding the histology of the parotid gland.

05:19 Now, the parotid glands are largely salivary glands in humans.

05:25 They secrete through the parotid duct into the mouth which we saw in our histology slide.

05:29 And now on histological examination, the parotid gland shows a capsule made of dense connective tissue, striated ducts lined in simple columnar epithelium and intercalated ducts lined with cuboidal epithelium.

05:45 Now, the parotid gland also shows an abundance of fat.

05:49 Now you don't see it there in the image so don't panic but you actually get more fat in the parotid gland with age.

05:56 And the parotid gland only contain serous acini while the other salivary glands, the sublingual and the submandibular glands contain both serous and mucinous acini.

06:08 This is very high yield to help you determine what type of gland tissue you're looking at.

06:12 Now since the question had mentioned sublingual glands, let's discuss the histology of the sublingual glands.

06:18 Now, sublingual glands are the smallest major salivary glands in humans.

06:24 They are the only salivary glands that are not encapsulated.

06:28 And on histological examination, the sublingual glands stain much less than do parotid glands due to the relatively small uptake of stain by their abundant mucinous acini.