Correct Answer: A

Rationale: The presence of a firm and immobile mass felt against the bowel wall during a rectal examination is concerning for a potential malignancy, such as colon cancer. Other conditions such as hemorrhoids or anal fissures are typically not associated with a mass that is firm and immobile. The "Valve of Houston" is a term that does not pertain to this scenario and is not a recognized medical entity. Therefore, the most likely diagnosis based on the given information is colon cancer, and further evaluation such as a colonoscopy would be warranted for definitive diagnosis and management.

Correct Answer: A

Rationale: The most significant risk factor for breast cancer in the patient's personal and family history is having a first-degree relative with premenopausal breast cancer. This is because the age at which a family member was diagnosed with breast cancer can be indicative of potential genetic predispositions that may increase the patient's own risk of developing the disease. Women with a first-degree relative who was diagnosed with breast cancer before menopause (premenopausal) are at a higher risk themselves compared to those with a family history of postmenopausal breast cancer. In this case, the patient's mother had unilateral breast cancer in her 70s, which suggests a higher risk compared to postmenopausal breast cancer. Other factors such as early age at menarche or age at first live birth are also important in assessing breast cancer risk, but having a first-degree relative with premenopausal breast cancer is the most significant

Correct Answer: C

Rationale: The description of the patient's left shoulder pain, with a sharp catching pain and a sensation of something grating during overhead movements, in addition to tenderness just below the tip of the acromion in the area of tendon insertions, is suggestive of calcific tendinitis. Calcific tendinitis occurs when calcium deposits form within a tendon, most commonly affecting the rotator cuff tendons. This condition can cause pain, tenderness, and limited range of motion, particularly with certain movements like overhead reaching. The negative drop arm test, lack of limitation with shoulder shrug, absence of tenderness to palpation in the bicipital groove, and the patient not holding his arm close to his side help differentiate calcific tendinitis from other shoulder pathologies like rotator cuff tendinitis, rotator cuff tear, and bicipital tendinitis.

Correct Answer: A

Rationale: The progression of excruciating pain starting under the lower ribs on the right side, then moving to the lateral abdomen, and finally settling in the right lower quadrant is classic for appendicitis. Appendicitis is an inflammation of the appendix, a small tube-like structure attached to the cecum (beginning of the large intestine). The pain typically starts around the umbilicus and then migrates to the right lower quadrant, where the appendix is located. Other symptoms that may accompany appendicitis include fever, nausea, vomiting, loss of appetite, and tenderness at McBurney's point (a specific area in the abdomen). It is a medical emergency that requires immediate attention to avoid complications such as perforation and peritonitis.

Correct Answer: A

Rationale: Rheumatoid arthritis is a systemic autoimmune disease that primarily affects the joints. It commonly presents with pain, swelling, and stiffness in multiple small joints such as those in the hands, wrists, and feet. It is more prevalent in females in their 30s to 50s. Rheumatoid arthritis is characterized by chronic inflammation of the synovial membrane, leading to joint damage and deformities over time. Laboratory tests showing elevated inflammatory markers, such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), along with positive rheumatoid factor and anti-cyclic citrullinated peptide (anti-CCP) antibodies, can help in confirming the diagnosis of rheumatoid arthritis.