MDS PREP
Indirect chemical carcinogens differ from direct acting agents in those
indirect agents:
1. Induce carcinogenicity without chemical transformation
2. Induce carcinogenicity after chemical transformation
3. Don’t require metabolic conversion
4. None of the above
Pathology Answer: 2
Indirect chemical carcinogens differ from direct acting agents in that they
require metabolic activation to exert their carcinogenic effects. This means
that indirect carcinogens must undergo a chemical transformation within the body
before they can damage DNA and induce cancer. Direct acting carcinogens, on the
other hand, can interact directly with DNA without the need for metabolic
conversion. Therefore, the correct answer is:
2. Induce carcinogenicity after chemical transformation
1. Induce carcinogenicity without chemical transformation: This statement is
incorrect for indirect chemical carcinogens. Indirect carcinogens are typically
non-reactive or less reactive in their original form and must undergo metabolic
activation to become DNA-reactive. This metabolic conversion is crucial for
their carcinogenic potential.
2. Induce carcinogenicity after chemical transformation: This is the correct
explanation. Indirect carcinogens require metabolic activation by the body's
enzyme systems, particularly phase I enzymes such as cytochrome P450, to convert
them into electrophilic or reactive intermediates that can interact with DNA.
This activation process can occur in various tissues, often the liver, where
these enzymes are present. The reactive metabolites then form DNA adducts, which
can lead to mutations and ultimately cancer if not repaired properly by the
cell's DNA repair mechanisms.
3. Don’t require metabolic conversion: This statement is incorrect. Indirect
carcinogens do require metabolic conversion to become active carcinogens. It is
the direct acting carcinogens that can interact with DNA without the need for
such activation because they are already electrophilic or reactive in their
original form.
A patient on warfarin sodium following myocardial infarction reports for an oral surgical procedure. Which one of the following laboratory tests should be preferred to ascertain the fitness
1. Prothrombin time
2. Tourniquet time
3. Clotting time
4. Bleeding time
Oral Pathology
Answer: 1
Prothrombin time should be preferred to ascertain fitness for extraction in a patient on warfarin.
What phenomenon is responsible when a person sets off the metal detector at the airport, despite removing watch, belt buckle, and every other obvious source of metal?
1) Argyria
2) Gall stones
3) Hemochromatosis
4) Kidney stones
General Pathology Answer: 3
Hemochromatosis is a condition characterized by excessive iron accumulation in the body, which can lead to a false positive on metal detectors due to high iron levels in tissues.
The histopathology of osteopetrosis shows
1. Endosteal bone formation and lack of normal bone resorption
2. Periosteal bone formation and lack of normal bone resorption
3. Presence of numerous osteoclasts and a few osteoblasts
4. None of the above
Oral Pathology
Answer: 1
The histopathology of osteopetrosis shows endosteal bone formation and lack of normal bone resorption.
Commonest type of Basal cell carcinoma is -
1. Ulcerated
2. Cystic
3. Morphoeic
4. Pigmented
Pathology
Answer: 1
1. Noduloulcerative Basal Cell Carcinoma: This is the most common subtype of
BCC, making up about 60-70% of all cases. It typically appears as a slowly
growing, round to oval, pearly or translucent nodule with a central ulceration
that may bleed or ooze. The borders of the lesion are often not well-defined and
may have a rolled, pearly edge with telangiectasias (small, dilated blood
vessels).
2. Cystic Basal Cell Carcinoma: This subtype presents as a round, dome-shaped
lesion with a cystic or fluid-filled center. It is less common than the
noduloulcerative type, and it may be mistaken for a benign cyst or epidermoid
cyst.
3. Morphoeic Basal Cell Carcinoma: Also known as sclerosing or morpheaform BCC,
this type is characterized by a slowly growing, ill-defined, firm, plaque-like
lesion that can infiltrate deeply into the skin. It may have a whitish, waxy
appearance with a scar-like texture. Morphoeic BCC tends to be more aggressive
and can be challenging to diagnose due to its subtlety.
4. Pigmented Basal Cell Carcinoma: This is a less common variant of BCC,
accounting for approximately 6-15% of cases. It presents with pigmentation in
the lesion, which can be brown, blue, or black. The presence of pigment can make
it look similar to melanoma, another type of skin cancer, so a biopsy is often
necessary to confirm the diagnosis.
Which of the following cell types show abnormal function when there is a history in a young adult of multiple arm and leg fractures following minor falls?
1) Granulocytic stem cells
2) Megakaryocytes
3) Plasma cells
4) Osteoclasts
Osteoclasts show abnormal function in conditions leading to multiple fractures, as they are responsible for bone resorption.
A case presenting with a gray coloured pseudomembrane whose removal is difficult and painful, can be
1) ANUG
2) Diphtheritic lesion
3) Secondary stage of syphilis
4) Desquamative gingivitis
Oral Pathology
Answer: 2
Diphtheritic lesions are caused by Corynebacterium diphtheriae. The hallmark of diphtheria is a tough gray pseudomembrane on mucosal surfaces like the pharynx or oral cavity. Attempting to remove it causes pain and bleeding. Other conditions like ANUG (acute necrotizing ulcerative gingivitis) produce pseudomembranes but are more localized and less gray.
Gingiva is most commonly affected by deficiency of
1. Vitamin A
2. Vitamin D
3. Vitamin C
4. Vitamin B
Oral Pathology
Answer: 3
Gingiva is most commonly affected by a deficiency of Vitamin C.