Cancers

#1
Most common cardiac tumor - metastasis
Most common primary cardiac tumor in adults - myxoma
Most common primary cardiac tumor in children - rhabdomyoma
Most common deficiency in HS - ankyrin
Most common tumor of appendix - adenocarcinoma
Most common heritable hematological disorder affecting humans - sickle cell anemia
Most common clinical feature of multiple myeloma - anemia
Most common M protein in multiple myeloma - IgM
Most common sites of involvement in myeloma - vertebrae > ribs > skull > pelvis > femur > clavicle > scapula

#2

Most common chromosomal anomaly in MDS - del 5q
Most common chromosomal anomaly in MDS in adults - del 5q
Most common chromosomal anomaly in MDS in children - monosomy 7
Most common site of carcinoid - GIT
Most common site of carcinoid in GIT - distal ileum > appendix
Most common congenital heart disease - VSD
Most common mode of Mendelian inheritance - autosomal recessive
Most common genetic cause of mental retardation - downs syndrome
Most common cause of pathological jaundice in newborn - Rh incompatibility

#3
Most common hematological malignancy in downs syndrome - ALL

Most common species of Malaria in India - Plasmodium falciparum (as per latest ICMR stats)
Most common cause of Nephrotic syndrome in adults - FSGS > membranous GN
Most common cause of Under five mortality - ARI > Diarrhoea
Most common cause of infant diarrhea - ETEC > EPEC (if asked about India)
If India not mentioned then EPEC > ETEC and same true for children also
Most common cause of death in Multiple myeloma - infections

#4

Most common AML with chloroma - M2
Most common AML with DIC - M3
Most common AML with gum hypertrophy - M5
Most common AML in Downs syndrome - M7
AML with best prognosis - M3
Most common hematological malignancy associated with Pure red cell aplasia- CLL
Most common cause of brain masses in hematologic malignancy - NHL
Most common of paraneoplastic skin disease -  Sweet syndrome or febrile neutrophilic dermatosis
Of patients with malignancy-associated Sweet syndrome, 85% have a hematologic malignancy, most commonly AML

#5

Most common soft tissue tumors in adults- Lipoma
Most common soft tissue sarcoma - Liposarcoma
Most common intracranial tumor-  secondaries
since all secondaries are malignant most common malignancy is also secondaries
Most common primary cns tumor -  meningioma 
Most common primary malignancy-  GBM

#6

Most common cause of primary hyperparathyroidism : Solitary parathyroid adenoma
Most common renal lesion in leprosy : membranous > membranoproliferative
Most commonly involved organ in Amyloidosis : Kidney
Most common cause of death in primary amyloidosis: Cardiac
Most common cause of death in secondary amyloidosis: Kidney.
Anastamosis in Whipple's which leaks the most: Pancreaticojejunostomy
Most common type of lymphoma to present with massive splenomegaly- splenic marginal zone lymphoma
Most common Lymphoma affecting spleen: NHL (Diffuse large B cell)
Most common primary benign neoplasm of the spleen: Hemangioma
Most common tumor of spleen: metastasis
(Reference Wintrobe's- Although still rare, carcinoma of the spleen from metastasis or direct tumor extension is more common than primary disease.)

#7

Most common altered oncogene in pancreatic cancer - KRAS
Most common inactivated tumor suppressor gene in pancreatic cancer - CDKN2A
Most common fungal infection of oral cavity - Candida albicans (It is a normal component of oral flora in 50% of the population!)
Most common form of candidiasis - Pseudo membranous (also called thrush)
Most common site of oral hairy leukoplakia - lateral border of tongue
Most common head and neck cancer - squamous cell carcinoma
Most common location for dentigerous cyst - Impacted third molar (wisdom tooth)
Most common odontogenic tumor - odontoma
Most common type of sinonasal papilloma - exophytic

#8

Most common underlying factor causing deformation - uterine constriction
Most common developmental defect of forebrain and midface - holoprosencephaly
Most common cause of neonatal mortality - congenital anomalies > prematurity
Most common cause of respiratory distress in neonates - hyaline membrane disease
Most common cause of death in patients with cystic fibrosis - cardiovascular > transplant associated > liver disease
Most common finding in infants who die of SIDS - multiple petechiae (thymus, visceral and parietal pleura, epicardium)
Most common teratomas in infancy - sacrococcygeal teratoma

#9

Most common type of emphysema - centriacinar (more than 95% of clinically significant cases, as per new Robbins)
Most common mass in anterior mediastinum - thymic neoplasm
Most common mass in middle mediastinum - cysts (bronchogenic)
Most common mass in posterior mediastinum - Neurogenic tumors
Most common mass in mediastinum (overall) - thymoma (adults) and neurogenic tumors (children)
Most common type of warm autoantibody - IgG
Most common type of cold autoantibody - IgM
(autoantibody in PCH is IgG)

#10

Most common neoplasm of salivary glands : Pleomorphic adenoma > Warthins tumor
Most common site of pleomorphic adenoma : Parotid
Most common tumor of parotid gland : Pleomorphic adenoma
Most common malignancy of minor salivary glands : Adenoid cystic carcinoma
Most common bilateral or multi focal salivary gland tumor : Warthin tumor (found exclusively in the parotid gland)
Most common salivary gland tumor in pediatric age group : Hemangioma > Pleomorphic adenoma
Most common malignant salivary gland tumor in pediatric age group : Mucoepidermoid carcinoma > Acinic cell carcinoma
Most common salivary gland malignancy : Mucoepidermoid carcinoma
Most aggressive primary salivary gland tumor :  Salivary duct carcinoma

#11

Most common cancer in India
Males :  lung
Females : cervix
If specifically asked for metropolitan females: breast

Most common cancer in world
Males : lung
Females : breast

Most common tumor to metastasize to breast : Malignant melanoma
Most common solid tumor to metastasize to breast :  Lung (small cell carcinoma)

#12

Most common site of primary in following secondary sites
1. Brain :  Lung
2. Lung : breast > colon > stomach > pancreas > kidney
3. Liver : carcinoma > lymphoma
Upper GI tract (stomach, gall bladder, pancreas) > colorectal > lung > breast
4. Bone : breast
5. Pleural effusion : bronchogenic carcinoma
6. Breast - malignant melanoma > lung
7. Ovary - colon
8. Thyroid - malignant melanoma > breast > kidney > lung

#13

Most common cancer to cause SVC syndrome : Breast cancer
Most common lung cancer to cause SVC syndrome : small cell > squamous
Most common cyst of spleen : pseudocyst
Most common true cyst of spleen : hydatid
Most common infectious cyst of spleen : hydatid
Most common tumor of spleen : hemangioma
Most common primary benign tumor of spleen : hemangioma
Most common malignant tumor of spleen : malignant lymphoma
Most common malignant primary non lymphoid tumor of spleen : angiosarcoma

#14

Most common sites of distant metastasis (other than regional lymph nodes) in following primary tumors-
1. Breast - skeletal system (lumbar vertebrae) > lung > liver
2. Kidney - lung > skeletal system (pelvis and femur)
3. Liver - lung
4. Lung - brain
5. Oesophagus - liver > lung > adrenal glands
6. Stomach - liver > peritoneum > lung 
7. Colorectal - liver
8. Ovarian serous carcinoma - contralateral ovary > peritoneal cavity
9. Prostate -  (osteoblastic, but can be osteolytic also) Lumbar spine > sacrum > pelvis
10. Malignant melanoma - liver > lung > git > bone > CNS