Routes of metastasis

Spread of cancer to distant sites is by following routes:-

Lymphatic spread :-

•Generally, carcinomas spread by lymphatic route and sarcomas spread through hematogenous route.However few sarcomas may also spread by lymphatic route.

• Involvement of lymph nodes by malignant cells is by:-

– lymphatic permeation :- The walls of the lymphatics are readily invaded by cancer cells and may form continuous growth in lymphatic channels called lymphatic permeation.

– lymphatic emboli :- Malignant cells may detach to form tumour emboli that may be carried along to the next lymph node. Tumour emboli will enter the lymph node by convex surface and gets lodged in subcapsular sinus and start growing . Later the lymph node will be enlarged and will be replaced by malignant tumour.

Characteristics of lymphatic spread:-

• Regional lymph nodes are invariably involved producing regional nodal metastasis. From carcinoma of the breast to axillary lymph nodes ; from the carcinoma of thyroid to cervical lymph nodes and however all regional nodal enlargements are not because of nodal metastasis.

• And sometimes, Lymphatic metastasis do not develop in the 1st lymph node which is nearest to the tumour because of venous lymphatic anastomoses or due to radiation , obliteration of lymphatics by inflammation so called skip metastasis.

• Other times due to obstruction of lymphatics by the tumour cells the lymph flow is disturbed and the tumour cells spread against the flow of lymph causing retrograde metastasis at unusual sites. Metastasis of carcinoma prostate to supraclavicular lymph nodes.

Virchows lymph node is nodal metastasis preferentially to supraclavicular lymph node from cancers of abdominal organs like cancer of stomach , colon.

Hematogenous spread :-

• Sarcomas usually spread by hematogenous route. And few carcinomas spread through hematogenous route.

Few features of hematogenous route are :-

• systemic veins drain blood to inferior vena cava from limbs , head and neck and pelvis so tumour of these organs will mostly metastasize to lungs.

• portal veins drains blood from bowel, pancreas and spleen to liver so, tumour of these organs are secondarily metastasize to liver.

Gross appearance of affected organ:-

There are multiple ; rounded nodules of varying size and scattered throughout the organ.

Microscopically:- primary tumour upon metastasis at different sites show varying degree of differentiation due to influence of local environment surrounding the tumour for its growth.

Spread along the body cavities and natural passages:-

• It’s the uncommon route of spread of tumour.

• Transcoelomic spread :- certain cancers invade through the serosal wall of the coelomic cavity so that the tumour cells or its fragments breaks off and will be carried in the coelomic fluid and gets implanted else where in the body. Most often involved is peritoneal cavity and less occasionally pleural and pericardial cavity.

– examples :- carcinoma of the stomach seeding to both ovaries (krukenberg tumour)

• Spread along the epithelium lined surfaces :- it’s unusual because intact epithelium and mucus are resistant to be penetrated by tumour cells. Examples :-are through the bronchus into alveoli.

• Spread via CSF:- Malignant tumours of ependyma and leptomeninges may spread by release of tumour cells through CSF.

• Implantation :- rare cases of reports of spread of some tumours is by implantation.

Reference :- Harsh mohan

Thrombus

• Thrombus is a blood clot in the circulatory system. It attaches to the site at which it is formed and remains there, hindering the blood flow.

• Thrombus is most likely to occur in the people who are immobile and those with a genetic predisposition to blood clotting.

• When a thrombus forms in an artery such as heart or brain is called arterial thrombosis.

• When a thrombus occurs in a vein is called venous thrombosis and if it occurs in deep veins it’s called deep vein thrombosis(DVT).

• Section of blood clot that breaks free from the thrombus and circulates in the bloodstream it’s called as an Embolus . Embolus is a dangerous and fatal complication of thrombosis.

Causes of thrombus:-

• Use of tobacco

• High cholesterol level

• Atherosclerosis

• Obesity

•Diabetes

•Stress

• Inactive life style

Symptoms of arterial thrombosis:-

• Unstable angina

• Myocardial infarction

• Ischaemic stroke

Symptoms of venous thrombosis :-

• pain , swelling and tenderness , usually in the calf

• Aching and warmth of the skin in the affected area

• Red skin, particularly at the back of the leg below the knee

DVT can be life threatening conditions ; emboli can travel through the bloodstream before blocking arteries elsewhere in the body.

Diagnosis:-

• Duplex ultrasound:- This is the most common test for diagnosing DVT. Duplex ultrasound uses the sound waves to create the images of the blood flowing through arteries and veins.

• A D – dimer test :- This test measures the levels of a substance in the blood that results from the breakdown of blood clots. High levels of this substance may indicate the presence of DVT or another type of blood clot.

• Venography:- A dye will be injected into the affected leg. This dye makes the vein visible on X ray such as fluoroscopy. If the scan shows a slower than the usual blood flow through the vein a thrombus may be present.

• MRI and CT scans

• A VQ scan it uses radioactive substance called radiotracer to reveal, on the scan ,the flow of Air and Blood within the lungs.

Treatment :-

• Surgery may be done in the case of medical emergency.

• Inferior vena cava (IVC) filters :- They are small mesh devices that a surgeon can put in the inferior vena cava under a local anesthetic. Inferior vena cava filters traps the blood clot and prevents them from reaching the heart and lungs. An IVC filter can be permanent or may be combined with anticoagulant therapy.

• Anticoagulants reduce the risk of clot forming and which also reduces the size of the thrombus.

• Compression stockings:- The stockings help to prevent calf pain and swelling and also reduces the risk of complications.

• Excercise :-usually recommended to stimulate blood circulation.

Source:- Medicalnewstoday.com

Granuloma

• Granuloma is defined as a circumscribed tiny lesion and it’s about 1 mm in diameter. Granuloma is derived from word granule means granule like lesion and oma suffix generally refers to tumour but here it refers to collection of macrophages.

• Granuloma is type 4 hypersensitivity reaction. It’s protective but sometimes leads to tissue destruction because of poorly digestible antigen.

Pathogenesis :-

• Macrophages and monocyte engulf the antigen and tries to destroy it since the antigen is poorly degradable these cells fail to destroy antigen and macrophages undergoes morphological changes and transform into epitheloid cells.

• As macrophages have failed to destroy antigen they present it to CD 4 T lymphocytes. Lymphocytes get activated and releases interleukin 1 and interleukin 2 that stimulate more T cells, interferon gamma activates macrophages.

• And also TNF alpha that promotes proliferation of fibroblasts and activates the endothelium to secrete prostaglandin and growth factors which stimulate fibroblast growth.

Composition of granuloma

Epitheloid cells are nothing but modified macrophages these are elongated cells and have slipper shaped nucleus . Nuclear chromatin is vesicular and lightly stained and cytoplasm is abundant and pale staining with hazy outlines.

Multinucleate giant cells formed by the fusion of adjacent epitheloid cells containing more than 20 nuclei. The nuclei may be arranged like horseshoe or ring or may be clustered at 2 poles ( langhans gaint cell seen in tuberculosis ) or may be present centrally ( foreign body giant cell seen in foreign body tissue reaction).

lymphoid cells as response to cell mediated immunity to antigen lymphocytes are the integral composition of granuloma. In some granulomas presence of plasma cells is indicative of humoral immune response.

Necrosis is a feature of some granulomataous conditions like TB.

Fibrosis is a feature of healing formed by fibroblast at the periphery.

So, Granuloma is having epitheloid cells at centre with interspersed gaint cells , surrounded peripherally lymphocytes and healing by fibroblast. Granuloma is a microscopic finding and it indicates chronic inflammation.

Reference :- Harsh mohan

Glass Ceramics

• Glass ceramics are the material that are initially formed as glass, and then transformed into ceramic usually by a controlled heat treatment.

• The heat induces partial devitrification which increases the strength as well as improves aesthetics by making it less transparent and more teeth like.

• The two glass ceramics used in dentistry are Castable glass ceramics and pressable glass ceramics.

• Advantages :- Ease of fabrication, Good aesthetics, improved strength and fracture toughness, Good marginal fit, very low processing shrinkage, low abrasion of opposing teeth.

Disadvantages :- Inadequate strength for posterior teeth.

Castable glass ceramics

•It’s properties are more closer to that of glass and it’s construction is quite different. This is only porcelain restoration that is made by centrifuging casting technique.

• The subsequent Ceramming process is also quite unique to this porcelain Ceramming will enhance the growth of mica crystals within the ceramic.

• It is first commercially available glass ceramic for dental use was Dicor.

• Composition :- Dicor glass ceramic contains 55% volume of Tetrasilicic fluoromica crystals.

• features :- The dicor glass ceramic crowns are very aesthetic. This is because of greater translucency (unlike the other porcelain which have more opaque core). It also picks up some of the color from adjacent teeth (chaemelon effect) as well as from underlying cement.

Uses:- inlays , onlays , veneers

Fabrication of a dicor crown:-

• wax pattern is constructed first and then invested with a refractory material.

• After burnout of the wax ,nuggets of the dicor glass are melted and cast into the mould in centrifuging casting machine.

• The glass casting is carefully recovered from the investment by sandblasting and the sprues are gently cut away.

•The glass restoration is then covered with embedment material to prepare it for next stage that is Ceramming.

• Ceramming is the heat treatment process by which the glass is strengthened. Ceramming results in the development of microscopic crystals of mica which

– improves the strength and toughness of glass

– improves the aesthetics of the restoration ( it reduces the transparency of the glass making it more opaque and less glass like)

• The cerammed glass can be built up with special veneering porcelain and fired to complete the restoration. Surface stains may be applied to improve the aesthetics.

Reference :- Manapalil text book of dental materials

Flexible denture base ( soft dentures)

•Our denture base is hard not flexible.So polyamide is added in flexible dentures to make them flexible and enhance the properties.

• Allergic reaction with conventional denture bases is because of free monomer and due to polymethyl methacrylate.

• Main properties of using flexible denture bases over the conventional ones are to avoid allergies to acrylic and metal and to improve retention.

• To improve aesthetic and make them more acceptable to patient.

• Flexible dentures help to avoid some kind of pain associated with old style denture models.

• Flexible denture bases helps to achieve greater stability and comfort.

• In addition to these benefits flexible denture are also designed to be porous and to breathe better.

• This helps to prevent the build up of bacteria on the denture.

• Nowadays it has become selective treatment of option. No more ugly metal wires.No more broken dentures.

• It is indicated in full dentures , partial dentures. Unique features of flexible denture Base are flexibility, strength, transparency, high impact resistance and high solvent resistance.

• Commercial names of flexible denture base are valplast, proflex, sunflex, unbreakable flexit plus dentures.

Reference :- Self notes