Benign neoplasm and tumor-like lesions
About 2 in 100 malignant tumors affect children worldwide. Macroscopically, neoplasm (true tumors) and a tumor-like lesion may look similar, however they present as different lesions.
While tumor-like lesions may look benign in nature, they may cause clinical problems based on size and location. We shall categorize tumor-like lesions based on two categories: heterotopia and hamartoma.
Heterotopia refers to microscopically normal cells or tissues found in an unusual location. E.g. rest of pancreatic tissue found in wall of stomach; adrenal cells found in lungs.
Hamartoma is the overgrowth of mature, well differentiated cells home to their organ of origin it occurs. E.g. Lymphangioma; hemangioma; cardiac rhabdomyomas; liver adenomas; developmental cysts of lungs. kidneys, pancreas.
Next, we shall differentiate all types of benign neoplasms and tumor-like lesions.
Hemangiomas
They are benign tumor-like lesions of blood vessel capillaries, that are flat or elevated irregular red-blue masses. Two types are cavernous and capillary hemangiomas.
Cavernous hemangiomas are present within some organs of the body cavities. E.g. brain, liver, eye.
Capillary hemangiomas form on the skin especially on the scalp, face and lower limb.
Lymphangioma and lymphangiectasis
Lymphangiomas are benign tumor-like cystic lesions of lymphatic origin usually found on neck, mediastinum, and axilla. Lymphangiectasis refers to subcutaneous dilation of deep lymphatic vessels which results in swelling of the extremities.
Mature and immature teratomas
Mature teratomas are benign well differentiated cystic tumors of germ cell line. They contain tissues including bone, skin, teeth, hair. Common locations include: tail bone, ovaries, testis. They may also be found on head and neck region, retroperitoneum, mediastinum. Usually in children <4 months of age.
Immature teratomas are benign cystic tumors usually containing fewer immature neuroepithelial stem cells than other mature tissue types (bone, teeth). They have the potential to become malignant. Usually affect children under 2 years of age.
Infantile fibrosarcoma
These are benign tumors of highly proliferating fibroblasts. They occur in children below 2 years of age and also have good prognosis.
Types of childhood malignant tumors
Unlike adults whose cancers are mainly of epithelial origin, majority of children’s malignancies are soft tissue tumors of mesenchymal origin. Except acute lymphoblastic leukemia & lymphoma, these malignant tumor cells are of embryonic origin still showing markers of organogenesis.
Many childhoods malignant tumors of embryonic origin are called “small round blue cell tumors”. The reason for this is that, the tumors appear as cells with round nuclei. Here is the list of malignancies usually in children below 10 years:
- Acute lymphoblastic leukemia
- Neuroblastoma
- Wilms tumor (Nephroblastoma)
- Hepatoblastoma
- Retinoblastoma
- Rhabdomyosarcoma
- Malignant teratoma
- Ewing sarcoma
- Juvenile astrocytoma
- Medulloblastoma
- Ependymoma
- Lymphoma
Adrenal neuroblastoma
This a type of neuroblastic tumor containing immature embryonic neural crest cells (neuroblasts). Histologically, they appear as small cells with dark nuclei, also having poorly defined borders. Usually diagnosed at about 18 months of age.
Clinical manifestations: Fever, large abdominal masses; weight loss; bone pain; respiratory or gastrointestinal symptoms; proptosis; ecchymosis; deep blue discoloration of skin (blueberry muffin baby).
Metastasis: They invade skin; periorbital region; liver; lungs; bone; bone marrow.
Diagnosis: Elevated levels of catecholamine; elevated urine levels of vanillylmandelic acid & homovanillic acid.
Wilms tumor
This is a malignant renal tumor of nephrogenic blastemal (embryonic) cell origin. Macroscopically, it usually presents as a single, solitary, well demarcated gray tumor. Wilms tumor also presents on both kidneys, and can be diagnosed in children below 10 years old.
Wilms tumor occurs due to germline mutation in one of the Wilms tumor-predisposing gene. Microscopically, it consists of sheets of small blue cells showing immature nephrogenic blastemal & differentiating mesenchymal, epithelial cells (tubules).
Clinical manifestations: Large abdominal mass; abdominal pain; hematuria; intestinal obstruction; hypertension. It commonly metastasizes to the lungs.
Malignant teratomas
Malignant teratomas are aggressive cystic tumors that contain more immature neuroepithelial stem cells than other mature tissue types (bone, teeth). They usually affect older children.
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