CAROTID BODY TUMOUR

CAROTID BODY TUMOUR

Q. 1 Carotid body tumor arises from? 
 A Not a tumour but called a tumor 
 B

Carotid artery

 C Parasympathetic paraganglioma
 D Symapthetic paraganglioma
Q. 1 Carotid body tumor arises from? 
 A Not a tumour but called a tumor 
 B

Carotid artery

 C Parasympathetic paraganglioma
 D Symapthetic paraganglioma
Ans. C

Explanation:

Parasympathetic paraganglioma REF: Harrison’s internal medicine 17th edition chapter 337, Devita 6th edition section 30.4

“Pheochromocytomas and paragangliomas are well-vascularized tumors that arise from cells derived from the sympathetic (e.g., adrenal medulla) or parasympathetic (e.g., carotid body, glomus vagale) paraganglia”

Most commonly, carotid body paragangliomas present as painless masses located deep to the anterior border of the sternocleidomastoid muscle in the upper or midneck. These are generally slow growing and often have been obvious for years before diagnosis. They are usually nonfunctional, but they do have the capability of function. Carotid body paragangliomas actually can grow to impressive dimensions without creating neurologic or vascular findings.


Q. 2 A man presented with a mass in the neck which is slow-growing. It is not causing pain or any other symptoms. On examination, it is a firm, non-tender pulsatile mass in the region of the carotid bifurcation. Diagnosis was made as carotid body tumor by angiogram. Where does carotid body tumor arise from?

 A Carotid sinus

 B

Carotid artery

 C

Parasympathetic paraganglioma

 D

Symapthetic paraganglioma

Ans. C

Explanation:

Paragangliomas are tumors arising from adrenal medulla or extra-adrenal paraganglia.

These include pheochromocytoma – intraadrenal paraganglioma, extraadrenal sympathetic paraganglioma, and extraadrenal parasympathetic paraganglioma, including tumors termed chemodectoma, and carotid body glomus tumor.

Sympathetic paragangliomas consist of endocrine cells which can produce catecholamines.

These tumors are located intraabdominally.

Parasympathetic paragangliomas develop from the paraganglias of parasympethicus such as paraganglium caroticum, jugulare, tympanicum and intravagale.

These tumors are predominantly found in the area of head, neck, and mediastinum.

Angiogram of carotid body tumor reveals widening of the carotid bifurcation with prominent tumor vascularization.

Ref: Stem Cells and Cancer Stem Cells, Volume 1: Stem Cells and Cancer Stem Cells … edited by M.A. Hayat, 2011, Page 38 ; Harrison’s internal medicine 17th edition chapter 337 ; Devita 6thedition section 30.4 ; Anatomic Basis of Tumor Surgery edited by William C. Wood, Charles Staley, John E. Skandalakis, 2010, Page 123


Q. 3

Which one is Not true regarding carotid body tumour

 A

Unilateral

 B

Surgical resection is the t/t

 C

Non cromaffin paraganglioma

 D

None

Ans. D

Explanation:

Ans is None

Carotid body tumor  (also k/a) chemodectoma or potato tumor)

  • The tumor arises from the chemoreceptor cells* on the medial side of carotid bulb
  • Histologically it is a non-chromaffin paraganglioma*
  • There is an association with pheochromocytoma*
  • Although chronic hypoxemia has been invoked as a stimulus for hyperplasia of carotid body, approximately 35% of carotid body tumors are hereditary.
  • Approximately 5 to 7% of carotid body tumors are malignant. The risk of malignancy is greatest in young patients with familial tumors.

Clinical features

  • Usually unilateral*
  • Present most commonly in the 5th decade* and approximately 10% have family history.
  • The pt. often presents with a long history of several years of a slowly enlarging painless lump* at the carotid bifurcation.
  • The mass is firm, rubbery, pulsatile and is mobile from side to side but not up and down, and can sometimes be emptied by firm pressure, after which it will slowly refill in pulsatile manner. A bruit may also be present. 

Investigation

  • Doppler study
  • Carotid angiogram
  • FNAC & biopsy are Ca

Treatment

  • Because these tumors rarely metastasize and their overall rate of growth is slow, the need for surgical removal must be considered carefully as complication of surgery are potentially serious.
  • The operation is best avoided in elderly patients.
  • Schwartz 8/e writes – “The treatment of choice of carotid body tumors is surgical excision. Because these tumors are highly vascularized, preoperative tumor embolization may be an advantage to minimize operative blood loss when dealing with tumors greater than 2 cm in diameter.

Q. 4

A 40 year old patient is suffering from carotid body tumor. Which of the following is the best choice of treatment for him‑

 A Excision of tumor

 B Radiotherapy

 C

Chemotherapy

 D

Carotid artery ligation both proximal and distal to the tumor

Ans. A

Explanation:

Ans. is ‘a’ i.e., Excision of tumor

  • Management of carotid body tumor: Resection is for cure and radiation for control.
  • But, operative intervention is best avoided in elderly patients.
  • Sometimes mass may not be separable from the vessels and resection will be necessary with graft for continuity in the carotid system.
  • Radiotherapy has no good effect.
  • The given patient is 40 years old (not elderly); hence, Excision or resection of the tumor will be the best treatment for him.

Q. 5 True about carotid body tumor-

 A

Arises from pharyngeal wall

 B

Arises from baroreceptor cells

 C

Commonly seen in high altitude habitants

 D

All

Ans. C

Explanation:

Ans is ‘c’ i.e. Commonly seen in high altitude habitants

  • Carotid body tumors arise from chemoreceptor cells of the carotid body (Baroreceptor cells are found in carotid sinus)
  • Since the chemoreceptor cells are stimulated by decreased arterial oxygen tension, a higher incidence of carotid body tumors is noted in oxygen-deprived individuals i.e. cyanotic heart disease, chronic hypoxia in high altitude inhabitants.
  • So it is a rare tumor that has a higher incidence in areas where people live at high altitudes because of chronic hypoxia leading to carotid body hyperplasia.

Q. 6 What is true about carotid body tumor ?

 A

Non-chromaffin paraganglioma

 B

Good prognosis

 C

Rarely metastasis

 D

All of the above

Ans. D

Explanation:

Ans. ‘D’ i.e. ‘A’Non-chromaffin Paraganglioma; ‘B’ i.e. Good Prognosis; ‘C’ i.e. Rarely metastasis

CAROTID BODY TUMOUR (Potato Tumour, Chemodectoma, Nonchromaffin Paraganglioma)

  • This is a rare tumor that has a higher incidence in areas where people live at high altitudes because of chronic hypoxia leading to carotid body hyperplasia.
  • The cells of the chemodectoma are not hormonally active and the tumors are usually benign with only a small number of cases producing proven metastasis.
  • The overall prognosis is quite good with complete surgical resection.

Q. 7 True for Carotid body tumours-

 A

Arises from the endothelial cells

 B

Originates from the Schwann cells

 C

Radiotherapy is the treatment of choice

 D

May metastasize

Ans. D

Explanation:

Ans. is ‘d’ i.e. May metastasize 

  • The carotid body originates from the third branchial arch and from neuroectodermal derived neural crest lineage.
  • The tumors arise from the chemoreceptor cells on the medial side of the carotid bulb and, at this point, the tumor is adherent to the carotid wall.
  • The cells of the chemodectoma are not hormonally active and the tumors are usually benign with only a small number of cases producing proven metastases.
  • Surgical resection is the recommended treatment for suspected carotid body tumors.

Q. 8 True about carotid body receptors ‑

 A

Most potent stimulus is high PCO2

 B

Dopamine is neurotransmitter

 C

Low blood flow

 D

Afferent through vagus nerve

Ans. B

Explanation:

Ans. is ‘b’ i.e., Dopamine is neurotransmitter

Peripheral chemoreceptors

The peripheral chemoreceptors which regulate respiration are located in the carotid body and aortic bodies. These bodies are located in the connective tissue associated with the vessel wall, at the bifurcation of the common carotid, and on the arch of aorta, respectively. The characteristic cells of both these structures are called glomus cells. Type I glomus cells have a high dopamine content, which they possibly employ as a neurotransmetter. Peripheral chemoreceptors convey information to the DRG of neurons in medulla, for which purpose the afferent neurons from the carotid bodies pass through glossopharyngeal nerve and from the aortic bodies pass through vagus nerve.

The most potent natural stimulus for peripheral chemoreceptors is low arterial P02 (hypoxic hypoxia). The other stimuli which activate peripheral chemoreceptors are high arterial PCO2, and an increase in arterial hydrogen ion concentration (acidosis or low pH). The response to activation of peripheral chemoreceptors is an increase in pulmonary ventilation through an increase in the rate and depth of breathing.

The blood flow to peripheral chemoreceptors, on per unit mass basis, is the highest to any tissue in the body. With a blood flow of 2000 ml/min/100 gm tissue, the carotid and aortic bodies, inspite of their high metabolic rate, hardly remove any oxygen from the blood supplies to them. That is why the arteriovenous oxygen difference is negligible in these bodies. Thus these structures are idealy built to sense change in arterial P02.

It is good to keep in mind that stimulation of peripheral chemoreceptors not only stimulates medullary respiratory centers but also medullary vasomotor center. Therefore, the response to their stimulation is tachycardia, vasoconstriction and increase BP along with hyperventilation.


Q. 9 True about carotid body tumor:

 A

Slow growing tumour

 B

Uncapsulated

 C

Mostly Bilateral

 D

Mostly benign

Ans. A:D

Explanation:

Answer- (A) Slow growing tumour (D) Mostly benign

Rare tumour occur b/w 3rd & 6th decade of life with slight female preponderance

A few are bilateral & some show familial incidence

Grossly they are small, firm, dark tan, encapsulated nodules

Tumours are usually benign with only a small number of cases producing proven metastases.

There is often a long history of a slowly enlarging, painless lump at the carotid bifurcation.



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