**Question:** Casals Necklace pattern is seen in

A. Pulmonary alveoli
B. Lymph nodes
C. Renal corpuscles
D. Hepatic lobules

**Core Concept:** Casals Necklace pattern is a histopathological term describing a specific arrangement of cells in certain organs. It is named after Dr. Pau Casals, a Spanish pathologist who first described this pattern in 1907.

**Why the Correct Answer is Right:** The Casals Necklace pattern refers to the characteristic arrangement of cells found in the renal corpuscles (also known as glomeruli) within the kidney. In this arrangement, the Bowman's capsule (a ring-shaped structure) is surrounded by a ring of cells called the capsular glomerulosclerosis. This pattern helps pathologists differentiate between different types of glomerulonephritis (inflammation of the glomeruli) and assess the severity of the disease.

**Why Each Wrong Option is Incorrect:**

A. Pulmonary alveoli: Pulmonary alveoli are the tiny air sacs in the lungs responsible for gas exchange with the bloodstream. The Casals Necklace pattern is not observed in the lungs.

B. Lymph nodes: Lymph nodes are immune system structures involved in filtering blood and presenting antigens. The Casals Necklace pattern is not found in lymph nodes.

C. Renal corpuscles: The Casals Necklace pattern is not observed in renal corpuscles, which are found within the kidney and are responsible for filtering blood and maintaining blood pressure.

D. Hepatic lobules: Hepatic lobules are clusters of hepatocytes (liver cells) in the liver. The Casals Necklace pattern is not found in the liver.

**Clinical Pearl:** The Casals Necklace pattern is a valuable diagnostic clue in renal histopathology, helping to identify the type of glomerulonephritis and assessing its severity. Understanding this pattern aids in accurate diagnosis and treatment planning for patients with kidney diseases.