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Developmental tumors and tumor like conditions. Dr Eman MS Muhammad. A malformation. It is an anatomical error arising during the development of an organism to its final adult proportions. Most malformations are manifest when the fetus is born .
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Developmental tumors and tumor like conditions Dr Eman MS Muhammad
A malformation • It is an anatomical errorarising during the development of an organism to its final adult proportions. • Most malformations are manifest when the fetus is born. • Some appears for the first time in the period of childhood or adolescence.
Sometimes malformations are concealed in the depth of the tissues. • They come for light only in later life as a result of some secondary changes in e.g: chordoma developing from the notochord remnants.
Forms or types of malformations: • Agenesis: Complete failure of development of an organ which is therefore absent – e.g. kidney. • Aplasia: Complete failure of development of a part which becomes rudimentary e.g. kidney. • Hypoplasia: The part may remain rudimentary and never attain a full mature size. • Failure of fusions: of parts leads to spina bifida, cleft palate. • Failure of separations: e.g. webbed digits. • Failure of canalization: e.g imperforate anus and vaginal atresia.
Local gigantism: e.g- enlarged digit or limb inneurofibromatosis. • It differs from hyperplasia and hypertrophy because the organ has never been normal in relation to the remainder of the body. • Supernumerary organs: double ureter, polydactyly and accessory spleens or spleniculi due to superfluity of parts resulting in the production of more than one organ. • Ectopia, heterotopia or aberrance: organs and tissues are found in abnormal sites. This may come about in one of 3 ways:
A. Persistence or growth of a tissue which normally atrophies or remains vestigial e.g: thyroid tissue may be found at the upper end of thyroglossal duct. B. Dislocation of part of a developing organ e.g. ectopic testis which may be present in the perineum or pelvis. C. Heteroplasia: This is the anomalous of differentiation of tissue e.g: presence of gastric mucosa in a Meckel’sdiverticulum, sebaceous glands may be found in the buccal mucosa as white, pin-point papules known as Fordyce’s spots.
Heteroplasia must be differentiated from metaplasia in which the alteration of tissue occurs after it has already differentiated to normally. • Choristomas: A forms of heterotopia closely related to benign tumors. These lesions contain normal tissues but are found in abnormal locations e.g. ectopic breast, liver, or other tissues. • Hamartoma:Atumor like mass composed of a haphazard mixture of tissues normally found in the part.
Finally: The malformed tissues may assume the independent proliferative activity of a true tumor.
Tumors derived from the germ cells • The germ cells first appear in the embryo in the wall of the yolk sac. • From where they migrate around the posterior of the primitive gut to the genital ridge on the posterior abdominal wall. • There; they are incorporated into the developing gonads which later descend into the pelvis or scrotum.
Some germ cells may either remain behind or stray from their final path and come to rest at various sites along the posterior wall of the embryo near the midline. • If these cells do not die, they could later give rise to tumors in these situations: the retroperitoneal area, the sacral region, the mediastinum, and the pineal region.
The greatest number of germ cell tumors occurs as would be expected in gonads e.g: • In males they form the most common type of malignant tumor in the 15-35 y age groups (seminoma), and the incidence appears to be increasing. • In female malignant germ cell tumors are uncommon and tend to occurs in children. • About 60% of germ cell tumors are composed of a single cell type.
Types of germ cell tumors • Seminoma and dysgerminoma. • Teratoma. • Extra-uterine choriocarcinoma. • Yolk sac tumor.
Teratoma • A tumor consisting of multiple tissues foreign to the part from which it arises and composed of the 3 germ layers i.e. ectoderm, mesoderm & endoderm (compound tumor). • This definition is applicable to well differentiated benignteratoma. • Some e.g testicular teratoma may be so undifferentiated, that their bulk composed of bizzareanaplastic cells which can not form any recognizable tissue at all.
Most teratomas occur in gonads, the ovary is much more affected than testis. • Origin:totipotent cells; premitive embryonic cells. • Sites: gonads (ovary & testis), retroperitoneal region, anterior mediastinum, sacrococcygeal region & base of the skull. • Age incidence: Commonly in infant & children. • Sometimes in young and middle age
Types: 1- Benign: Common. • Cystic: dermoid cyst, more common. • Solid: less common. 2- Malignant: rare. • Ovarian teratomas are usually benign & cystic. • Testicular teratomas are usually malignant & solid. • Spread: Common by blood.
Ovarian teratomas • Results from differentiation of a germ cell into embryonic tissues types: A. Benign cystic teratoma (dermoid cyst): • Most cases of ovarian teratomas. • It occurs in females in young and middle age group and accounts for 15-20% of all ovarian neoplasm.
Grossly: • It takes a form of large rounded or oval thin walled cyst which has a smooth outer surface (5-15 cm in diameter). • It is usually unilateral. • Cut section: • It is usually unlocular, rarely multilocular, contains matted hair and sebaceous matter. • In one portion of the wall there is an eminence or “umbo” which composed of teeth and contains bone and cartilage.
Microscopically: • The cyst is lined with stratified squamousepithelium and skin appendages are prominent in the wall. • This appearance gives it a misleading name “dermoid cyst” but unlike “true dermoid cyst” other tissues are also present especially in the area of the umboe.g: intestinal or respiratory epithelium, bone, cartilage or foci of nervous tissue.
Two other distinct variants of benign cystic teratoma are: I. Struma ovarii: • It is a very rare tumor, in which a benign cystic teratoma shows predominance of thyroid tissue, which forms the entire bulk of the tumor. II. Ovarian carcinoid tumor: • In this type the tissue in the cyst consists of purecarcinoid tumor. • Effects of strumaovarii: • It may become toxic with signs and symptoms of thyrotoxicosis. • It may turn malignant to one of the pictures of thyroid carcinomas.
Malignant (solid or cystic teratoma): • Grossly: • It is a very rare tumor which usually arises as a malignant change in a previous benign teratoma, but it may begin as a malignantteratoma from the start. • It is usually seen in children and young women and is usually solid.
Microscopically: • If it occurs on top of benign cystic form, it is commonly squamous cell carcinoma. • If it starts as a malignant teratoma, it shows a variety of undifferentiated tissues like that of testicular teratomas. • Spread: • Blood spread to the lung. • Prognosis: • It is good with modern chemotherapy.
Testicular teratomas • It occurs in young and middle aged men, peak incidence is the 20 y in contrast to seminoma which occurs in older age group.
Grossly: • In contrast to ovarian teratomas, testicular teratomas are usually solid and almost always malignant. • The affected testis is asymmetrically enlarged and firm in consistency. • Cut surface shows solid yellow or white tissue and differs from seminoma in that areas of hemorrhage and necrosis are common. • Multiple small cysts are seen in the well differentiated forms, filled with serous or blood stained fluid.
Teratoma of the testis consisting of a disorganized collection of glands, cartilage, smooth muscle, and immature stroma.
Microscopically: • The picture varies according to the degree differentiation into: A. Malignant teratoma differentiated MTD (WHO mature teratoma): • Uncommon tumor occurs often in children and made up of haphazardly arranged well differentiated tissue and is similar in appearance to benign ovarian teratoma. • However unlike ovarian dermoid; MTD are mainly solid and contains small cysts.
They may metastasize even though all the various elements seen are mature and cytologically benign. • This is probably because small foci of less well differentiated tissue are present and remains undetected despite extensive histological sampling. • For this reason all MTDs should be regarded as malignant.
B. Malignant teratoma intermediate MTI (WHO immature teratoma): • It is the commonest form of testicular teratoma. • These tumors consist of a mixture of tissues showing variable degrees of differentiation. • In addition many contain clearly malignant elements which may be carcinomatous, sarcomatous or anaplastic.
C. Malignant teratoma undifferentiated MTU (WHO embryonal carcinoma): • This tumor consists of malignant tissue resembling the malignant elements of MTI. • The commonest pattern is composed of masses of large pleomorphic malignant cells. • Many areas show attempts at adenocarcinomatous or papillary differentiation.
D. Malignant trophoblasticteratoma MTT (testicular choriocarcinoma): • It is malignant teratoma with trophoblastic differentiation. • The germ cells differentiate along placental or yolk sac lines. • It carries a very poor prognosis even with modern therapy.
The initial tumor is small and the initial presentation may be hemoptysis from hemorrhagic pulmonary metastases. • Trophoblastic tissue produces H.C.G. • Prognosis and spread: • Malignant teratomametastasize rapidly both by the lymphatic and the blood stream.
The embryonic tumors of infancy • Unlike teratoma which contains a wide variety of body’s tissues, this group of tumors consists only of those elements present in a particular part of the body e.g: the kidney, liver, retina, brain. • It would appear that during the development of these particular areas a perversion of organogenesis occurs. • A part of the developing organ undergoes neoplastic transformation and a tumor which is usually highly malignant may result.
Some of these lesions may present at birth, but most developing within the first 5 years of life at a time when the tissues are continuing their development. • Very rarely some cases may develop in adults and it assumed that the lesion has remained latent until later life or that it has developed from a “cell rest”.
Classifications: A. Tumors arising from embryonic cells after differentiation (pluripotent cells), giving rise to tumors of the same variety i.e. ectoderm only, mesoderm only or endoderm. • They are called mixed tumours e.g. nephroblastoma, hepatoblastoma …..etc. B. Malignant tumors arising from unipotent cells; which can differentiate into one type of tissue of embryonic nature (blast cells). • They are called simple tumors e.g. neuroblastoma, medulloblastoma, retinoblastoma, chondroblastoma ….etc.
Types of embryonic tumors of infancy • Nephroblastoma or Wilm’s tumor (Kidney) • Hepatoblastoma (Liver) • Neuroblastoma (Sympathetic ganglia and adrenal medulla) • Medulloblastoma (Brain) • Retinoblastoma (Eye) • Embryonic sarcoma, rhabdomyosarcoma or sarcoma botryoides (vagina and urinary bladder)
Hamartoma • It is a tumor-like focal malformation in which the tissues of a particular part of the body are arranged haphazardly usually with the excess of one or more of its components. • It is composed of tissue elements normally found at that site, but they are growing in a disorganized manner. • It resembles a neoplasm in its origin, but it is not a malignanttumor; it grows at the same rate as the surrounding tissue.
Hamartomas occur in many different parts of the body, and are most often asymptomatic incidentalomas (undetected until they are found incidentally on an imaging study obtained for another reason e.g. 1. The typical example is the cartilagenous mass commonly found in the lung 2-3 cm in diameter and has a white pearly appearance and is hard in consistency.
In section it is composed of mature hyaline cartilage similar to that in the bronchus. • It contains respiratory epithelium, smooth muscle and connective tissue. • There is no true capsule between the lesion and the surrounding lung parenchyma. • It is “mixed” but all its elements are normally present in the lung. • It is derived from a developing bronchus.
2. Hamartoma of the kidney 3. Hemangiomas 4. Lymphangiomas 5. Cancellous and ivory osteoma, multiple exostosis 6. Multiple neurofibromatosis 7. Melanotichamartoma or navei
The definition of hamartoma versus benign neoplasm is often unclear, since both lesions can be clonal. • Lesions such as adenomas, developmental cysts, hemangiomas, lymphangioma, and rhabdomyomas within the kidneys, lungs, or pancreas are interpreted by some experts as hamartomas while others consider them true neoplasms.
Moreover, even though hamartomas show a benign histology, there is a risk of some rare but life-threatening clinical issues such as those found in neurofibromatosis type I and tuberous sclerosis.
Differences between hamartoma and choristomas • Choristomas, forms of heterotopia, are closely related benign tumors, found in abnormal locations. • The two can be differentiated as follows: a hamartoma is an excess of normal tissue in a normal situation (e.g., a birthmark on the skin), while a choristoma is an excess of tissue in an abnormal situation (e.g., pancreatic tissue in the duodenum).
Differences between hamartoma and teratoma • The tissues present are these specificto the part from which it arises in case of hamartoma, but in teratoma it is foreign. • In hamartoma the tissue has no-tendency towards excessive growth. Its growth is coordinated with that of the surrounding tissues, and it stops after adolescence. • There is no capsule around a hamartoma, and there is no pressure atrophy as its growth proceeds “paripassu”with that of the surroundings.
Hamartomas are not true tumors, but it is possible for a tumor to develop in a hamartoma. • Many tumors are given “tumor sounding” names e.gangioma, chondroma of the lung. • Most hamatroma are present at birth or in early childhood, but only those on exposed areas like skin and mouth will be diagnosed early. • Hamartoma of the lung may be discovered during routine x-ray chest examination and misdiagnosed as carcinoma.
I. Vascular hamartomas: A. Hemangioma: • It is a mass of blood vessels atypical or irregular in arrangement and size. • It is hamartomatous malformation and is not a true tumor, although now some considered it a benign tumor of the blood vessels. • It is usually present at birth or appears soon afterwards, their growth ceases with the growth of the patient. • They comprise a mixture of vascular and other mesenchymal elements.
Grossly: • The commonest type is seen in the skin as a variety of “nevus”. • N.B: “Nevus” is a word which describes any type of developmental blemish of the skin (birth mark). • It is soft well defined or slightly raised, red, blue or purple, non capsulated lesion. • It is sometimes small and spider like, sometimes flattened and extensive covering a considerable part of the skin “port wine stain or nevus flammeus”, sometimes it forms raised “strawberry nevi”.
