Endocrine Pathology Practice Questions

Q: Gs alpha mutation is associated with all of the following except?

Papillary carcinoma thyroid. **Explanation:** The **Gsα (GNAS1 gene)** mutation leads to the constitutive activation of adenylate cyclase, resulting in the overproduction of cAMP. This pathway acts as a potent mitogen in several endocrine tissues. **Why Papillary Carcinoma Thyroid (PTC) is the correct answer:** Papillary carcinoma of the thyroid is primarily associated with mutations in the **MAPK pathway**, most commonly the **BRAF V600E mutation** (found in ~60% of cases) or **RET/PTC rearrangements**. Gsα mutations are not a feature of PTC. **Analysis of Incorrect Options:** * **McCune-Albright Syndrome:** Caused by a **post-zygotic somatic mutation** in GNAS1 [1]. It presents with the triad of polyostotic fibrous dysplasia, café-au-lait spots, and autonomous endocrine hyperfunction (e.g., precocious puberty). * **Pituitary Adenomas:** Somatic mutations in Gsα (specifically the **gsp oncogene**) are found in approximately 40% of **Somatotroph (GH-secreting) adenomas** [1]. The mutation mimics the action of GHRH, leading to persistent GH secretion. * **Pseudohypoparathyroidism (PHP):** Specifically Type 1a (Albright’s Hereditary Osteodystrophy), which involves an **inactivating mutation** of the Gsα protein. This leads to end-organ resistance to PTH, resulting in hypocalcemia and hyperphosphatemia despite elevated PTH levels. **High-Yield Clinical Pearls for NEET-PG:** * **GNAS1 Mutation:** If *activating*, it leads to McCune-Albright or Pituitary adenomas [1]. If *inactivating*, it leads to Pseudohypoparathyroidism. * **Follicular Thyroid Carcinoma:** Associated with **RAS mutations** or **PAX8-PPARG** translocations. * **Medullary Thyroid Carcinoma:** Associated with **RET proto-oncogene** mutations (MEN 2A/2B). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, pp. 1079-1081.

Q: Gastrin is a biochemical marker for which of the following tumours?

Pancreatic neuroendocrine tumour. **Explanation:** **Gastrin** is a peptide hormone primarily produced by the G-cells of the gastric antrum. In a pathological context, it serves as a specific biochemical marker for **Gastrinomas** [1], which are a type of **Pancreatic Neuroendocrine Tumour (PanNET)**. These tumours (often located in the "Gastrinoma Triangle") secrete excessive gastrin, leading to **Zollinger-Ellison Syndrome (ZES)**, characterized by refractory peptic ulcers and severe diarrhea [1]. **Analysis of Options:** * **Medullary Carcinoma of Thyroid (MCT):** The classic biochemical marker is **Calcitonin**. Carceaembryonic Antigen (CEA) is also used for monitoring. * **Pheochromocytoma:** This tumour of the adrenal medulla secretes catecholamines. The diagnostic markers are urinary and plasma **Metanephrines** and Vanillylmandelic acid (VMA). * **Gastrointestinal Stromal Tumor (GIST):** This is a mesenchymal tumour, not a neuroendocrine one. Its hallmark is the expression of **CD117 (c-KIT)** and **DOG1** on immunohistochemistry. **High-Yield Clinical Pearls for NEET-PG:** * **Zollinger-Ellison Syndrome:** Suspect this when ulcers are multiple, distal to the duodenum, or recur after treatment [1]. * **MEN1 Syndrome:** Gastrinomas are the most common functional pancreatic neuroendocrine tumours associated with Multiple Endocrine Neoplasia Type 1 (The 3 P’s: Pituitary, Parathyroid, Pancreas) [1]. * **Diagnostic Test:** The **Secretin Stimulation Test** is the provocative test of choice; secretin causes a paradoxical *increase* in serum gastrin levels in gastrinoma patients. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, pp. 1124-1125.

Q: Which of the following statements is false regarding medullary carcinoma of the thyroid?

Arises from follicular cells. **Explanation:** **1. Why Option A is False (The Correct Answer):** Medullary Thyroid Carcinoma (MTC) does **not** arise from follicular cells. Instead, it originates from the **Parafollicular cells (C-cells)**, which are derived from the **ultimobranchial body (neural crest cells)**. Follicular cells give rise to differentiated thyroid cancers like Papillary and Follicular carcinoma. **2. Analysis of Other Options:** * **Option B (Secretes Calcitonin):** This is true. Since MTC arises from C-cells, it produces **Calcitonin**, which serves as a highly specific tumor marker for diagnosis and monitoring recurrence. * **Option C (Occurs in families):** This is true. Approximately 25% of MTC cases are hereditary, occurring as part of **MEN 2A, MEN 2B**, or Familial MTC syndromes, usually associated with the **RET proto-oncogene** mutation. * **Option D (Amyloid in stroma):** This is true. A classic histological hallmark of MTC is the presence of **amyloid deposits** in the stroma, which represent pro-calcitonin fibrils stained by **Congo Red** (showing apple-green birefringence). **Clinical Pearls for NEET-PG:** * **Tumor Marker:** Calcitonin (for diagnosis) and CEA (for prognosis). * **Genetic Testing:** All patients with MTC must be screened for **RET mutations** and co-existing **Pheochromocytoma** (especially before surgery). * **Spread:** Unlike papillary CA (lymphatic) or follicular CA (hematogenous), MTC spreads via **both** routes. * **Management:** Total thyroidectomy with central compartment neck dissection is the treatment of choice; it is **not** responsive to radioactive iodine (RAI) because C-cells do not take up iodine.

Question 1

Which of the following is characteristic of Hashimoto's thyroiditis?

Accepted Answer

Orphan Annie eye nuclei

Answer

Follicular destruction

Answer

Increase in lymphocytes

Answer

Oncocytic metaplasia

Question 2

Gs alpha mutation is associated with all of the following except?

Accepted Answer

Papillary carcinoma thyroid

Answer

McCune-Albright syndrome

Answer

Pituitary adenomas

Answer

Pseudohypoparathyroidism

Question 3

Gastrin is a biochemical marker for which of the following tumours?

Accepted Answer

Pancreatic neuroendocrine tumour

Answer

Medullary carcinoma of thyroid

Answer

Pheochromocytoma

Answer

Gastrointestinal stromal tumor

Question 4

GNAS mutation is associated with malignancy of which of the following pituitary cell types?

Accepted Answer

Somatotrophs

Answer

Lactotrophs

Answer

Thyrotrophs

Answer

Corticotrophs

Question 5

Which is the most common gene mutation responsible for papillary thyroid cancer?

Accepted Answer

BRAF

Answer

RET

Answer

RAS

Answer

p53

Question 6

Which of the following is associated with the RET proto-oncogene?

Accepted Answer

Medullary carcinoma of thyroid

Answer

MEN1

Answer

Small cell carcinoma of lung

Answer

Melanoma

Question 7

Waterhouse-Friderichsen Syndrome is:

Accepted Answer

Massive adrenal hemorrhage following disseminated bacterial infection

Answer

Adrenal failure due to rapid withdrawal of steroids

Answer

Massive adrenal hemorrhage following difficult delivery in neonates.

Answer

Adrenal crisis in individuals with chronic adrenocortical insufficiency precipitated by any form of stress

Question 8

Thyroid carcinoma with pulsatile vascular skeletal metastasis is:

Accepted Answer

Follicular

Answer

Papillary

Answer

Medullary

Answer

Anaplastic

Question 9

Which of the following statements is false regarding medullary carcinoma of the thyroid?

Accepted Answer

Arises from follicular cells

Answer

Secretes calcitonin

Answer

Occurs in families

Answer

Amyloid in stroma

Question 10

A 58-year-old man with a long-standing history of type 2 diabetes mellitus suffers a massive hemorrhagic stroke and expires. Examination of the pancreas shows hyalinization of many islets of Langerhans. Which of the following characterizes the material within the islets of Langerhans?

Accepted Answer

Amyloid

Answer

Collagen type IV

Answer

Fibrin

Answer

Fibronectin

Endocrine Pathology — MCQs

Endocrine Pathology — MCQs

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