Metastatic Tumors 

These are the most common malignant tumor of bone. Certain tumors exhibit a distinct skeletal prediliction. In adults more than 75% of skeletal metastases originate from cancers of the prostate, breast, kidney, and lung. In children, neuroblastoma, Wilms' tumor, osteosarcoma, Ewing sarcoma, and rhabdomyosarcoma are the common sources of bony metastases. Most metastases involve the axial skeleton (vertebral column, pelvis, ribs, skull, sternum), proximal femur, and humerus. The radiologic appearance of metastases can be purely osteolytic, purely osteoblastic, or mixed osteolytic-osteoblastic (majority of cases). In lytic lesions (e.g., kidney& lung), the metastatic cells secrete substances such as prostaglandins, interleukins, etc. that stimulate osteoclastic bone resorption; the tumor cells themselves do not directly resorb bone. Similarly, metastases that elicit a blastic response (e.g., prostate adenocarcinoma) do so by stimulating osteoblastic bone formation.

Abnormalities in chromosome number
Trisomy 21 (Down syndrome)
(1) The most common chromosomal disorder.
(2) A disorder affecting autosomes. It is generally caused by meiotic nondisjunction in the mother, which results in an extra copy of chromosome 21 or trisomy 21.
(3) Risk increases with maternal age.
(4) Clinical findings include mental retardation and congenital heart defects. There is also an increased risk of developing acute leukemia
and an increased susceptibility to severe infections.
(5) Oral findings include macroglossia, delayed eruption of teeth, and hypodontia.

Trisomies 18 and 13
(1) Trisomy 18 (Edwards syndrome):
characterized by an extra copy of chromosome 18. Oral findings include micrognathia.
(2) Trisomy 13 (Patau’s syndrome): characterized by an extra copy of chromosome 13. Oral findings include cleft lip and palate.
(3) Meiotic nondisjunction is usually the cause of an extra chromosome in both of these trisomies.
(4) Clinical findings for both of these trisomies are usually more severe than trisomy 21. Most children with these diseases die within months after being born due to manifestations such as congenital heart disease.

Klinefelter’s syndrome
(1) One of the most common causes of male hypogonadism.
(2) Characterized by two or more X chromosomes and one or more Y chromosomes. Typically, there are 47  chromosomes with the karyotype of XXY.
(3) The cause is usually from meiotic nondisjunction.
(4) Clinical findings include atrophic and underdeveloped testes, gynecomastia, tall stature, and a lower IQ.

Turner’s syndrome
(1) One of the most important causes of amenorrhea.
(2) Characterized by having only one X chromosome, with a total of 45 chromosomes and a karyotype of XO.
(3) Clinical findings include underdeveloped female genitalia, short stature, webbed neck, and amenorrhea. Affected females are usually
sterile. Unlike other chromosomal disorders, this one is usually not complicated by mental retardation.

Treacher Collins syndrome (mandibulofacial dysostosis)
(1) Genetic transmission: autosomal dominant.
(2) A relatively rare disease that results from abnormal development of derivatives from the first and second branchial arches.
(3) Clinical findings include underdeveloped zygomas and mandible and deformed ears. Oral findings include cleft palate and small or absent parotid glands.

NEOPLASIA

 An abnormal. growth, in excess of and uncoordinated with normal tissues Which persists in the same excessive manner after cessation of the stimuli which evoked the change.

Tumours are broadly divided by their behaviors into 2 main groups, benign and malignant.

Through most tumours can be classified in the benign or malignant category . Some exhibits an intermediate behaviours.

CLASSIFICATION

Some tumours can not be clearly categorized in the above table e.g.

• Mixed tumours like fibroadenoma of the breast which is a neoplastic proliferation of both epithelial and mesenchmal tissues.
• Teratomas which are tumours from germ cells (in the glands) and totipotent cells

(in extra gonodal sites like mediastinun, retroperitoneum and presacral region). These are composed of multiple tissues indicative of differentiation into the derivatives of the three germinal layers.

• Hamartomas which are malformations consisting of a haphazard mass of  tissue normally present at that site.

 LUNG ABSCESS  Lung abscess is a localised area of necrosis of lung tissue with suppuration.

 It is of 2 types:

 - Primary lung abscess that develops in an otherwise normal lung. The commonest cause is aspiration of infected material.

 - Secondary lung abscess that develops as a complication of some other disease of the lung or from another site

ETIOPATHOGENESIS.

 The microorganisms commonly isolated from the lungs in lung abscess are streptococci, staphylococci and various gram-negative organisms. These are introduced into the lungs from one of the following mechanisms:

 1.   Aspiration of infected foreign material.

 2. Preceding bacterial infection.

 3.  Bronchial obstruction.

 4. Septic embolism.

 5. Miscellaneous (i) Infection in pulmonary infarcts, (ii) Amoebic abscesses, (iii) Trauma to the lungs. (iv) Direct extension from a suppurative focus.

Abscesses may be of variable size from a few millimeters to large cavities, 5 to 6 cm in diameter. The cavity often contains exudate. An acute lung abscess is initially surrounded by acute pneumonia and has poorly-defined ragged wall. With passage of time, the abscess becomes chronic and develops fibrous wall.

Microscopic Examination

The characteristic feature is the destruction of lung parenchyma with suppurative exudate in the lung cavity. The cavity is initially surrounded by acute inflammation in the wall but later there is replacement by exudate of lymphocytes, plasma cells and macrophages. In more chronic cases, there is considerable fibroblastic proliferation forming a fibrocollagenic wall.

Herpes simplex is subdivided into type 1 and 2, the former usually developing lesions around the lips and mouth and the latter producing vesicular lesions in the genital region 
 - contracted by physical contact; incubation 2-10 days.
 - primary HSV I usually is accompanied by systemic signs of fever and Lymphadenopathy, while recurrent herpes is not associate with systemic signs.
 - dentists often become infected by contact with patient saliva and often develop extremely painful infections on the fingers (herpetic whitlow).
 - Herpes viruses remain dormant in sensory ganglia and are reactivated by stress, sunlight, menses, etc. 

 - Herpes gingivostomatitis is MC primary HSV 1 infectionÆpainful, vesicular eruptions that may extend for the tongue to the retropharynx.
 - Herpes keratoconjunctivitis (HSV 1)
 - Kaposi's varicelliform eruption refers to an HSV 1 infection superimposed on a previous dermatitis, usually in an immunodeficient person.
 - laboratory: culture; ELISA test on vesicle fluid; intranuclear inclusions within multinucleated squamous cells in scrapings (Tzanck preps) of vesicular lesions. 

Pneumoconioses—are environmentally related lung diseases that result from chronic inhalation of various substances.

1. Silicosis (stone mason’s disease) 
a. Inhalant: silica dust.
b. Associated with extensive fibrosis of the lungs.
c. Patients have a higher susceptibility to tuberculosis infections.

2. Asbestosis
a. Inhalant: asbestos fibers.
b. Associated with the presence of pleural plaques.
c. Consequences include:
(1) Mesothelioma (malignant mesothelial tumor).
(2) Bronchogenic carcinoma.

3. Anthracosis
a. Inhalant: carbon dust.
b. Usually not as harmful as silicosis or asbestosis.
c. Associated with the presence of macrophages containing carbon.