1. Human papillomavirus types 6 and 11 → condyloma acuminta (venereal warts).
2. Molluscum contagiosum is characterized by a bowl shaped lesion filled with keratin, the latter containing the viral inclusions (molluscum bodies) in the squamous cells. 

Bone-Forming Tumors

1. Osteoma is a benign lesion of bone that in many cases represent a developmental abnormaly or reactive growth rather than true neoplasms. They are most common in the head, including the paranasal sinuses. 
Microscopically, there is a mixture of woven and lamellar bone. They may cause local mechanical problems (e.g., obstruction of a sinus cavity) and cosmetic deformities. 

2. Osteoid Osteoma and Osteoblastoma 
are benign neoplasms with very similar histologic features. Both lesions typically arise during the 2nd & 3rd decades. They are well-circumscribed lesions, usually involving the cortex. The central area of the tumor, termed the nidus, is characteristically radiolucent. Osteoid osteomas arise most often in the proximal femur and tibia, and are by definition less than 2 cm, whereas osteoblastomas are larger. Localized pain is an almost universal complaint with osteoid osteomas, and is usually relieved by aspirin. Osteoblastomas arise most often in the vertebral column; they also cause pain, which is not responsive to aspirin. Malignant transformation is rare unless the lesion is treated with radiation. 

Gross features

• Both lesions are round-to-oval masses of hemorrhagic gritty tan tissue.
• A rim of sclerotic bone is present at the edge of both types of tumors. 

Microscopic features
• There are interlacing trabeculae of woven bone surrounded by osteoblasts.
• The intervening connective tissue is loose, vascular & contains variable numbers of giant cells.

3. Osteosarcoma

This is “a bone-producing malignant mesenchymal tumor.” Excluding myeloma and lymphoma, osteosarcoma is the most common primary malignant tumor of bone (20%). The peak age of incidence is 10-25 years with 75% of the affected patients are younger than age 20 years; there is a second peak that occurrs in the elderly, usually secondary to other conditions, e.g. Paget disease, bone infarcts, and prior irradiation. Most tumors arise in the metaphysis of the long bones of the extremities, with 60% occurring about the knee, 15% around the hip, & 10% at the shoulder. The most common type of osteosarcoma is primary, solitary, intramedullary, and poorly differentiated, producing a predominantly bony matrix.

Gross features

• The tumor is gritty, gray-white, often with foci of hemorrhage and cystic degeneration.
• It frequently destroys the surrounding cortex to extend into the soft tissue.
• There is extensive spread within the medullary canal, with replacement of the marrow. However, penetration
of the epiphyseal plate or the joint space is infrequent.

Microscopic features

• Tumor cells are pleomorphic with large hyperchromatic nuclei; bizarre tumor giant cells are common, as are mitoses.
• The direct production of mineralized or unmineralized bone (osteoid) by malignant cells is essential for diagnosis of osteosarcoma. The neoplastic bone is typically fine, lace-like but can also be deposited in broad sheets.
• Cartilage can be present in varying amounts. When malignant cartilage is abundant, the tumor is called a chondroblastic osteosarcoma.

Pathogenesis

• Several genetic mutations are closely associated with the development of osteosarcoma. In particular, RB gene mutations that occur in both sporadic tumors, and in individuals with hereditary retinoblastomas. In the latter there are germ-line mutations in the RB gene (inherited).
• Spontaneous osteosarcomas also frequently exhibit mutations in genes that regulate the cell cycle including p53, cyclins, etc.

Osteosarcomas typically present as painful enlarging masses.

Radiographs usually show a large, destructive, mixed lytic and blastic mass with infiltrating margins. The tumor frequently breaks the cortex and lifts the periosteum. The latter results in a reactive periosteal bone formation; a triangular shadow on x-ray between the cortex and raised periosteum (Codman triangle) is characteristic but not specific of osteosarcomas.
Osteosarcomas typically spread hematogenously; 10% to 20% of patients have demonstrable pulmonary metastases at the time of diagnosis. 

Coccidioidomycosis (Valley Fever; San Joaquin Fever)

A disease caused by the fungus Coccidioides immitis, usually occurring in a primary form as an acute benign asymptomatic or self-limited respiratory infection, occasionally disseminating to cause focal lesions in skin, subcutaneous tissues, lymph nodes, bones, liver, kidneys, meninges, brain, or other tissues.

Primary coccidioidomycosis is usually asymptomatic, but nonspecific respiratory symptoms resembling influenza or acute bronchitis sometimes occur or, less often, acute pneumonia or pleural effusion. Symptoms, in decreasing order of frequency, include fever, cough, chest pain, chills, sputum production, sore throat, and hemoptysis.

Progressive disseminated coccidioidomycosis may develop a few weeks, months, or occasionally years after primary infections,, is more common in men than women and is more likely to occur in association with HIV infection, immunosuppressive therapy

Symptoms often are nonspecific, including low-grade fever, anorexia, weight loss, and weakness. Extensive pulmonary involvement may cause progressive cyanosis, dyspnea, and discharge of mucopurulent or bloody sputum. Extrapulmonary lesions are usually focal, involving one or more tissue sites in bones, joints, skin, subcutaneous tissues, viscera, brain, or meninges. Draining sinus tracts sometimes connect deeper lesions to the skin. Localized extrapulmonary lesions often become chronic and recur frequently, sometimes long after completion of seemingly successful antifungal therapy.

Aneurysm

An aneurysm is a localized abnormal dilation of a blood vessel or the heart

Types:
1. True aneurysm - it involves all three layers of the arterial wall (intima, media, and adventitia) or the attenuated wall of the heart.
 e.g. Atherosclerotic, syphilitic, and congenital aneurysms, and ventricular aneurysms that follow transmural myocardial infarctions. 

2 False aneurysm 
(also called pseudo-aneurysm) is a breach in the vascular wall leading to an extravascular hematoma that freely communicates with the intravascular space ("pulsating hematoma"). 
E.g. ventricular ruptures after MI that are contained by a pericardial adhesion
E.g. a leak at the junction of a vascular graft with a natural artery.

Aneurysms are classified by macroscopic shape and size 
Saccular aneurysms 

spherical outpouchings (involving only a portion of the vessel wall, and often contain thrombi. 

Fusiform aneurysms

diffuse, circumferential dilation of a long vascular segment; 

they vary in diameter and length and can involve extensive portions of the aortic arch, abdominal aorta, or even the iliacs.

Aortic Aneurysm 

The two most important causes are: 

1- atherosclerosis : the most common cause 
It causes thinning and weakening of the media. The intimal plaques compress the underlying media and also compromise nutrient and waste diffusion from the vascular lumen into the arterial wall. The media consequently undergoes degeneration and necrosis, thus allowing the dilation of the vessel 

2- cystic medial degeneration of the arterial media. E.g. Marfan syndrome.

3- Other causes include: trauma, congenital defects (e.g., berry aneurysms), infections (mycotic aneurysms), systemic diseases, such as vasculitis.

Mycotic  Aneurysm :  
Infection of a major artery that weakens its wall is called a mycotic aneurysm

possible complications: thrombosis and rupture. 

It can originate from: 
(1) embolization of a septic thrombus, usually as a complication of infective endocarditis 
(2) extension of an adjacent suppurative process; 
(3) circulating organisms directly infecting the arterial wall 

Mycotic AAAs are atherosclerotic lesions infected by lodging of circulating microorganisms in the wall 

- e.g.  bacteremia from a primary Salmonella gastroenteritis. 

Abdominal Aortic  Aneurysm

Atherosclerotic aneurysms occur most frequently in the abdominal aorta ,the common iliac arteries, the arch, and descending parts of the thoracic aorta can also be involved 

Pathogenesis 

AAA occurs more frequently in men and rarely develops before age 50. 

Atherosclerosis is a major cause of AAA 

 hereditary defects in structural components of the aorta (e.g., defective fibrillin production in Marfan disease affects elastic tissue synthesis) 
 
 Morphology :
  Usually positioned below the renal arteries and above the bifurcation of the aorta 
  
  AAA can be saccular or fusiform 
  
  as large as 15 cm in diameter, and as long as 25 cm. 
  
  Microscopically: atherosclerosis with destruction and thinning of the underlying aortic media 
  
  the aneurysm frequently contains a laminated mural thrombus
  
  Syphilitic Aneurysm 
  
  Caused by The spirochetes T. pallidum 
  
  Tertiary stage of syphilis can cause obliterative endarteritis of the involve small vessels in any part of the body, including the vasa vasorum of the aorta 
  
  This results in ischemic medial injury, leading to aneurysmal dilation of the aorta and aortic annulus, and eventually valvular insufficiency. 
  
  valvular insufficiency and massive volume overload lead to hypertrophy of the left ventricle. The greatly enlarged hearts are sometimes called "cor bovinum" (cow's heart).
  
  CLINICAL CONSEQUENCES
  
  1.  Rupture → massive potentially fatal hemorrhage 
  2. Obstruction of downstream vessel → tissue ischemic injury
  3. Embolism → from atheroma or mural thrombus 
  4. Impingement and compression on an adjacent structure 
  5. Presentation as an abdominal mass 

Hypopituitarism

Hypopituitarism is caused by

1. Loss of the anterior pituitary parenchyma
    a. congenital 
    b. acquired  
    
2. Disorders of the hypothalamus e.g. tumors; these interfere with the delivery of pituitary hormone-releasing factors from the hypothalamus.  

Most cases of anterior pituitary hypofunction are caused by the following:
1. Nonfunctioning pituitary adenomas 
2. Ischemic necrosis of the anterior pituitary is an important cause of pituitary insufficiency. This requires destruction of 75% of the anterior pituitary. 

Causes include  

a. Sheehan syndrome, refers to postpartum necrosis of the anterior pituitary, and is the most cause. During pregnancy the anterior pituitary enlarges considerably because of an increase in the size and number of prolactin-secreting cells. However, this physiologic enlargement of the gland is not accompanied by an increase in blood supply. The enlarged gland is therefore vulnerable to ischemic injury, especially in women who develop significant hemorrhage and hypotension during the peripartum period. The posterior pituitary is usually not affected. 

b. Disseminated intravascular coagulation 
c. Sickle cell anemia 
d. Elevated intracranial pressure 
e. Traumatic injury
f. Shock states

3. Iatrogenic i.e.  surgical removal or radiation-induced destruction
4. Inflammatory lesions such as sarcoidosis or tuberculosis
5. Metastatic neoplasms involving the pituitary. 
6. Mutations affecting the pituitary transcription factor Pit-1 

Children can develop growth failure (pituitary dwarfism) as a result of growth hormone deficiency.

Gonadotropin or gonadotropin-releasing hormone (GnRH) deficiency leads to amenorrhea and infertility in women and decreased libido, impotence, and loss of pubic and axillary hair in men. TSH and ACTH deficiencies result in symptoms of hypothyroidism and hypoadrenalism. Prolactin deficiency results in failure of postpartum lactation. 

Eosinophilia:
Causes

-Allergic disorders.
-Parasitic infection.
-Skin diseases.
-Pulmonary eosinophilia.
-Myeloproliferative lesions and Hodgkin's disease.