USMLE USMLE Certifications USMLE-STEP-1 Questions & Answers

• Question 321:

  A 52-year-old woman presents to her primary care physician complaining of increasing fatigue and mild shortness of breath. Blood work reveals a hypochromic anemia with a hemoglobin concentration of 10.4 g/ dL, MCV of 76 / , MCHC of 29 g/dL, and a decrease in the absolute reticulocyte count.

  

  WBC and platelet counts are within normal limits. Serum iron and ferritin levels are low and total iron-binding capacity is elevated. Which of the following conditions best accounts for these findings?

  A. anemia of chronic disease

  B. aplastic anemia

  C. hypothyroidism

  D. iron deficiency

  E. pernicious anemia

  Correct Answer: D

  Section: Pathology and Path physiology Laboratory findings of a hypochromic anemia with a decrease in MCV and MCHC indices and a decreased reticulocyte count suggest a hypoproliferative anemia. The various microcytic, hypochromic anemias belong to this category and a partial differential diagnosis for these includes iron-deficiency anemia, anemia of chronic disease (ACD) (choice A), thalassemias, and sideroblastic anemias. ACD (choice A) may be distinguished from irondeficiency anemia by additional iron studies, as were performed in this case. While serum iron and ferritin levels are low and total ironbinding capacity (TIBC) is elevated in irondeficiency anemia, in ACD ferritin is typically normal or elevated, iron is low, and TIBC is low. ACD is associated with a functional, not an absolute, deficiency in iron as a result of sequestration by reticuloendothelial cells. Aplastic anemia (choice B) causes a pancytopenia, which was not the case in this patient as WBC and platelet levels were normal. Hypothyroidism (choice C) and pernicious anemia (choice E) are megaloblastic anemias, which demonstrate increased, not decreased, MCV values (~ >110 fL).

• Question 322:

  A 15-month-old girl presents with a large abdominal mass, weight loss, and fever. At surgery, a large infiltrative tumor with areas of hemorrhage and necrosis is removed. A photomicrograph of a section from this tumor is shown in below figure. Which of the following is the most likely diagnosis?

  

  A. embryonal rhabdomyosarcoma

  B. malignant lymphoma

  C. neuroblastoma

  D. teratoma

  E. Wilms' tumor

  Correct Answer: C

  Section: Pathology and Path physiology This is a neuroblastoma and is one of a group of childhood tumors described as "small, round, blue-cell tumors," consisting as they do of monotonous small cells with dense, blue nuclei. The characteristic microscopic feature of a neuroblastoma is the pseudorosette, a ring of primitive neuroblasts surrounding a central space filled with fibrillar extensions from the cells. Many of these can be seen in figure. These are called pseudorosettes because they do not have a central lumen as is found, for example, in the rosettes in retinoblastoma. Embryonal rhabdomyosarcoma (choice A) is a type of rhabdomyosarcoma typically found in children under the age of 10. It can arise in a number of locations and sarcoma botryoides is one form. It does not form rosettes. Malignant lymphomas (choice B) and leukemias are together the most common malignancies of childhood in the United States, but rosette formation is not a distinctive microscopic feature. Teratomas (choice D) in infants and young children are usually benign tumors found in the midline (e.g., sacrococcygeal, mediastinal). They are composed of tissues with a normal histologic appearance derived from all three germ layers. Wilms' tumor (choice E) or nephroblastoma is derived from primitive blastema cells and sometimes displays aborted attempts to form glomeruli or renal tubules, but not rosettes.

• Question 323:

  A 28-year-old recently divorced man with no significant past medical history presents to the emergency room with progressive lower abdominal pain and cramping over the past 4 days, both of which are relieved by defecation. He has suffered from substantial bloody and mucoid diarrhea during this time. His temperature is 102.8癋. Laboratory studies reveal a n elevated white blood cell (WBC) count and a high erythrocyte sedimentation rate. Sigmoidoscopy reveals extensive rectal and sigmoid hyperemia and edema, numerous superficial ulcerations, and small focal mucosal hemorrhages, many of which have suppurative centers. Significant intestinal narrowing is seen in the distal transverse colon. These findings most likely suggest a diagnosis of which of the following?

  A. amebic colitis

  B. collagenous colitis

  C. cytomegalovirus enterocolitis

  D. pseudomembranous colitis

  E. ulcerative colitis

  Correct Answer: E

  Section: Pathology and Path physiology Clinical history and sigmoidoscopy findings are consistent with a diagnosis of ulcerative colitis, an idiopathic inflammatory bowel disease that involves the rectum in virtually all cases and extends proximally in a continuous manner without skip lesions to include variable lengths of the colon. Psychological stress (recent divorce) may serve to precipitate acute attacks of the disease. The significant narrowing seen in the transverse colon in this patient suggests the possible progression to toxic megacolon, a rare complication in severe acute disease that carries a high mortality rate and requires emergency colectomy. Amebic colitis (choice A) is characterized by acute inflammation with multiple areas of enzymatic tissue necrosis leading to submucosal, flask-shaped abscesses throughout the colon. Clinical features include bloody and mucoid diarrhea with low-grade fever. Collagenous colitis (choice B) is a more recently recognized form of colitis characterized clinically by episodic or chronic watery diarrhea that is not severe enough to cause dehydration, and pathologically by the presence of a distinct collagenous band beneath the colonic surface epithelium. Patients very often have a variety of autoimmune and other diseases. Cytomegalovirus enterocolitis (choice C) is a common GI infection in acquired immunodeficiency syndrome (AIDS) patients that infects the entire GI tract and produces severe, chronic diarrhea. Both mucosal epithelial and vascular endothelial cells are infected. Vasculitis may result in focal ischemic necrosis of the intestinal wall. Pseudomembranous colitis (choice D) is caused by a necrolytic enzyme produced by Clostridium difficile bacteria that most often proliferate secondary to a variety of antibiotic therapies; clindamycin is a frequent culprit. Diarrhea is most often watery and profuse. Gross findings include patchy areas of mucosal inflammation with multiple, discrete yellowish plaques constituting the pseudomembrane, which is composed of fibrin, mucin, and necrotic debris.

• Question 324:

  A 57-year-old woman had her last menstrual period at the age of 46. However, for the past 4 months she has experienced intermittent vaginal hemorrhage. A right ovarian mass is identified. Which of the following is the most likely diagnosis?

  A. arrhenoblastoma

  B. Brenner tumor

  C. dysgerminoma

  D. granulosa cell tumor

  E. Sertoli-Leydig cell tumor

  F. teratoma

  Correct Answer: D

  Section: Pathology and Path physiology An ovarian mass raises the possibility of a tumor and vaginal hemorrhage in a postmenopausal woman and suggests an estrogenproducing tumor. One of the first estrogenproducing tumors to consider is granulosa cell tumor. Arrhenoblastoma (Sertoli-Leydig cell tumor) (choice A) secretes androgens, not estrogens. Brenner tumor (choice B) is an uncommon ovarian neoplasm without hormonal activity. Dysgerminoma (choice C) is the female counterpart of the male seminoma and does not produce hormones. Sertoli-Leydig cell tumor (choice E) is a synonym for arrhenoblastoma (choice A). Teratoma (choice F) is also hormonally inactive.

• Question 325:

  A 14-year-old boy is referred to you for nasal obstruction and frequent nosebleeds. Which of the following is the most likely diagnosis?

  A. inverted papilloma

  B. juvenile angiofibroma

  C. nasal polyps

  D. nasopharyngeal carcinoma

  E. wegener granulomatosis

  Correct Answer: B

  Section: Pathology and Path physiology Juvenile angiofibroma is a very vascular tumor originating in the nasopharynx that is typically found in teenage boys and young adult males. It may lead to obstruction and, because of its vascularity, it is a frequent cause of epistaxis. It should be suspected in any teenage boy with frequent epistaxis. Inverted papilloma (choice A) is a benign tumor but is aggressive locally and can erode into surrounding structures. Rather than having an exophytic growth pattern, it grows down (thus inverted) into other structures and may be difficult to excise completely. It can cause unilateral obstruction and occasionally epistaxis but is generally seen in an older age group (50s). Nasal polyps (choice C) are not tumors but edematous growths commonly found in patients with allergic rhinitis. They produce chronic nasal obstruction and a gradual loss of olfaction. Nasopharyngeal carcinoma (choice D) is associated with Epstein-Barr virus and is another potential cause of obstruction and hemorrhage but again is seen in older patients. Wegener granulomatosis (choice E) is a necrotizing granulomatous vasculitis involving the nose sinuses, lungs, and kidneys. It occurs most frequently in the fifth and sixth decades.

• Question 326:

  A 50-year-old woman complains of a lump in her thyroid gland. Fine-needle aspiration of this lump is reported as medullary carcinoma. A test of her serum would most likely reveal an increased level of which of the following?

  A. alpha-Fetoprotein

  B. cancer antigen (CA) 125

  C. CA 153

  D. calcitonin

  E. human chorionic gonadotropin

  Correct Answer: D

  Section: Pathology and Path physiology Calcitonin is a hormone secreted by the parafollicular C cells of the thyroid gland. Medullary carcinoma arises from malignant transformation of these cells. Alpha-fetoprotein (choice A) may be elevated in the serum in association with hepatocellular carcinomas and gonadal tumors. CA 125 (choice B) is a tumorassociated glycoprotein frequently expressed by ovarian carcinomas. CA 153 (choice C) is a tumor-associated glycoprotein frequently expressed by breast carcinomas. Elevations of human chorionic gonadotropin (choice E) in the serum may be seen in normal pregnancies, gonadal tumors, and choriocarcinomas.

• Question 327:

  Alung autopsy specimen with an abnormality of the vasculature is depicted in below figure. What is the most likely associated clinical finding?

  

  A. chronic idiopathic thrombocytopenic purpura

  B. disseminated intravascular coagulation

  C. hemoptysis due to aneurysmal rupture

  D. hemoptysis due to tumor eroding into blood vessel

  E. sudden death due to occlusive embolus

  Correct Answer: E

  Section: Pathology and Path physiology figure depicts a large occlusive embolus in the pulmonary artery. Clinically, this finding is most frequently associated with the formation of deep venous thrombi; sudden death may occur with thromboemboli large enough to lodge in the pulmonary artery bifurcation (saddle embolus). Chronic idiopathic thrombocytopenic purpura (choice A) is an unlikely milieu to form thromboemboli due to the paucity of platelets. Both hemorrhage and thrombosis may occur in disseminated intravascular coagulation (choice B); however, this condition affects the microvasculature, not large vessels. The figure does not display an aneurysm (choice C) or a neoplasm (choice D).

• Question 328:

  A 2-day-old male infant has not passed any meconium and is now developing signs of obstruction. Examination of the colon would reveal which of the following abnormalities?

  A. absence of parasympathetic ganglion cells in the submucosal and myenteric plexus

  B. absence of the nerve fibers that innervate the wall

  C. atrophy of the mucosal lining of the wall

  D. hypertrophy of the muscle coat of the wall

  E. presence of multiple small polyps along the mucosal surface

  Correct Answer: A

  Section: Pathology and Path physiology Hirschsprung disease is caused by the congenital absence of parasympathetic ganglion cells in the submucosal and myenteric plexus. This presents clinically soon after birth as an inability to pass stool and abdominal distention. The diagnosis is usually confirmed by a full-thickness colon biopsy showing disorganized, nonmyelinated nerve fibers replacing the missing ganglion cells. In Hirschsprung disease, the ganglion cells, not the nerve fibers (choice B), are missing. Muscular hypertrophy (choice D) and atrophy (choice C) are not specific diagnostic findings with Hirschsprung disease. Mucosal polyp development (choice E) is not associated with Hirschsprung disease.

• Question 329:

  A 67-year-old woman presents with a 4-week history of headaches, facial pain, blurred vision, and intense pain and stiffness in her shoulders and hips. She is diagnosed with a vasculitis, and a biopsy of an affected artery is taken. Histological examination is most likely to reveal which of the following characteristic findings?

  A. concentric "onion skin" thickening and fibrosis

  B. extensive intra- and extravascular granulomatous inflammation

  C. fragmentation of the internal elastic lamina with giant cells

  D. hyaline arteriolosclerosis and luminal narrowing

  E. segmental fibrinoid necrosis and neutrophil infiltration

  Correct Answer: C

  Section: Pathology and Path physiology The most likely diagnosis in this case is giant cell (temporal) arteritis; it is both the most common systemic vasculitis in this woman's age group (>60) and is suggested by the clinical history. Giant cell arteritis may affect any medium- and large-sized arteries, but principally involves vessels in the head, that is, extracranial branches of the carotid arteries. Vascular insufficiency leads to symptoms of jaw or facial pain, headaches, and visual changes, as reported by this patient. In particular, ischemic optic neuropathy may occur abruptly, resulting in permanent blindness; for this reason, patients with ocular disturbances in suspected cases demand immediate medical intervention. Temporal arteritis has a strong, well-known association with polymyalgia rheumatica, a systemic inflammatory disorder causing symmetrical, often severe muscle pain and stiffness in the shoulders and pelvic girdle (also reported by this patient); both conditions are associated with the HLA-D4 haplotype. Microscopically, a section of a vessel affected by giant cell arteritis will demonstrate fragmentation of the internal elastic lamina and the presence of multinucleated giant cells. Concentric "onion skin" thickening and fibrosis (choice A) may be seen most commonly in malignant hypertension but also in other conditions such as primary sclerosing cholangitis. Extensive intra- and extravascular granulomatous inflammation (choice B) refers to Wegener granulomatosis which often includes: (i) acute necrotizing granulomas of the upper and/or lower respiratory tract; (ii) granulomatous vasculitis; and (iii) renal disease. Hyaline arteriolosclerosis and luminal narrowing (choice C) is found in association with benign hypertension and in diabetes mellitus but is also seen in some normotensive, nondiabetic elderly individuals. Segmental fibrinoid necrosis and neutrophil infiltration (choice E) is a description of the acute phase of polyarteritis nodosa.

• Question 330:

  A 67-year-old retiree was employed for many years in the plastics industry where he was exposed to vinyl chloride. This industrial exposure has increased his likelihood of developing which of the following?

  A. focal nodular hyperplasia

  B. hepatic adenoma

  C. hepatic angiosarcoma

  D. hepatic fibroma

  E. hepatocellular carcinoma

  Correct Answer: C

  Section: Pathology and Path physiology Environmental exposure to vinyl chloride is associated with the later development of hepatic angiosarcoma. Focal nodular hyperplasia (choice A) and hepatic fibroma (choice D) do not at present have well-defined antecedent environmental exposure histories. Hepatic adenomas (choice B) occur sporadically in the setting of exogenous steroid hormone usage. Hepatocellular carcinoma (choice E) is associated with cirrhosis, chronic viral hepatitis, and aflatoxin exposure.