A dermatofibroma is a benign tumor of the dermis, MC located on the lower extremity, where it has a nodular, pigmented appearance.
 - composed of benign histiocytes.

Bacillus anthrax
 - large Gram (+) rods that produce heat resistant spores; Clostridia and Bacillus species are the two bacterial spore formers; they do not form spores in tissue; produces a powerful exotoxin.
 - contracted by direct contact with animal skins or products  
 
 - four forms of anthrax are recognized → cutaneous (MC), pulmonary, oraloropharyngeal, and gastrointestinal.
 - cutaneous anthrax (90 to 95% of cases) occurs through direct contact with infected or contaminated animal products.
 - lesions resemble insect bites but eventually swell to form a black scab, or eschar, with a central area of necrosis ("malignant pustule").

Molecular techniques

Different molecular techniques such as fluorescent in situ hybridization, Southern blot, etc... can be used to detect genetic diseases.

EMBOLISM 

An embolus is a detached intravascular solid, liquid, or gaseous mass that is carried by the blood to a site distant from its point of origin

99% due to dislodged thrombus

Types: 
1. Thrombo-embolism 
2. Fat embolism 
3. Air embolism 
4. Nitrogen embolism

 Emboli result in partial or complete vascular occlusion. 

 The consequences of thromboembolism include ischemic necrosis (infarction) of downstream tissue

PULMONARY THROMBOEMBOLISM
- 95% originate from deep veins of L.L

Special variants: - Saddle embolus: at bifurcation of Pulmonary artery

Paradoxical embolus: Passage of an embolus from venous to systemic circulation through IAD, IVD

CLINICAL CONSEQUENCE OF PULMONARY THROMBOEMBOLISM :

Most pulmonary emboli (60% to 80%) are clinically silent because they are small 

a. Organization: 60 – 80 % 
b. Sudden death, Right ventricle failure, CV collapse when more than 60 % of pulmonary vessels are obstructed. 
c. Pulmonary hemorrhage: obstruction of medium sized arteries. 
d. Pulmonary Hypertension and right ventricular failure due to multiple emboli over a long time.

Systemic thromboembolism

Emboli traveling within the arterial circulation 
80% due to intracardiac mural thrombi
2/3  Lt. ventricular failure

 The major targets are: 
 
 1. Lower limbs 75% 
 2. Brain 10% 
 3. Intestines 
 4. Kidneys 
 5. Spleen

Fat embolism 

Causes 
1. Skeletal injury (fractures of long bones ) 
2. Adipose tissue Injury

Mechanical obstruction is exacerbated by free fatty acid release from the fat globules, causing local toxic injury to endothelium. - In skeletal injury, fat embolism occurs in 90% of cases, but only 10% or less have clinical findings

 Fat embolism syndrome is characterized by 
 
 A. Pulmonary Insufficiency 
 B. Neurologic symptoms 
 C. Anemia 
 D. Thrombocytopenia 
 E. Death in 10% of the case 
 
 Symptoms appears 1-3 days after injury
 
 Tachypnea, Dyspnea, Tachycardia and Neurological symptoms
 
Air Embolism 

causes: 1. Obstetric procedures 
2. Chest wall injury 
3. Decompression sickness: in Scuba and deep-sea divers ((nitrogen )) 

 More then 100ml of air is required to produce clinical effect. 
 
 Clinical consequence
 1. Painful joints: due to rapid formation of gas bubbles within Sk. Muscles and supporting tissues. 
 2. Focal ischemia in brain and heart 
 3. Lung edema, Hemorrhage, atelectasis, emphysema, which all lead to Respiratory distress. (chokes) 
 4. caisson disease: gas emboli in the bones leads to multiple foci of ischemic necrosis, usually the heads of the femurs, tibias, and humeri
 
 Amniotic fluid embolism 
 - Mortality Rate = 20%-40% 
 - Very rare complication of labor 
 
 - due to infusion of amniotic fluid into maternal circulation via tears in placental membranes and rupture of uterine veins. 
 - sudden severe dyspnea, cyanosis, and hypotensive shock, followed by seizures, DIC and coma 
 
 - Findings: Squamous cells, languo hair, fat, mucin …..etc within the pulmonary microcirculation

DYSPLASIA
 It is disturbed growth or  cells in regard to their size, shape arrangement. In its mild degrees it represents a reversible reaction to chronic inflammation whereas the most severe degrees warrant a labelling of intraepithelial neoplasia. Hence it includes a wide spectrum of changes ranging from a reversible disorientation to 'carcinoma-in-situ'.

Histologically it is characterized by:

o    Basal cell hyperplasia.
o    Variation in size and shape of cells.
o    Disorderly maturation.
o    Increased mitotic activity.
o    Disorientation of arrangement of cells (loss of polarity)

Dysplasia is commonly seen in:

o    Squamous epithelium of cervix.
o    Bronchial epithelium in habitual smokers.
o    Gastric and colonic mucosa in long standing inflammation
o    Oral and vulval leucoplakia
 

Nevus
1. Commonly known as moles.
2. A benign, pigmented tumor of melanocytes, found deep within connective tissue.
3. Types of skin nevi:
a. Junctional nevus—found in the epidermis.
It is the only type of nevus that may be considered to be premalignant.
b. Compound nevus—found in both the epidermis and underlying dermis.
c. Intraepidermal nevus—found in the dermis.