Tumor Pathology

Tumor Pathology

Concept:

• Tumor is a neoplastic mass caused by abnormal, excessive, and autonomous proliferation of transformed body cells.

• Tumor is cell proliferation triggered by mutations (MUT).

• MUT causing the disease gives tumor cells the ability to survive, grow, and proliferate vigorously independently of normal physiological signals (autonomous proliferation).

Distinguish between tumor and pseudotumor:

• Pseudotumor is a lesion that does not have the ability to proliferate autonomously.

• Examples of pseudotumor (pseudo-tumor lesions):

• Nasal polyp

• Thyroid goiter

• Harmatoma in the lungs

• Choristom (ectopic pancreatic tissue in the stomach)

Tumor classification:

• Benign tumor:

• Slow growth

• Localized, does not spread to other areas

• Completely recovered after surgery, rarely fatal

• Example: Meningioma can be fatal.

• Malignant tumor:

• Fast growth

• Invade the surrounding area, distant metastasis

• Usually fatal

• Example: Basal cell carcinoma of the skin is rarely fatal.

• Borderline malignant tumor:

• Degree of malignancy is unclear, unpredictable progression

• Slow progression

• Invade the surrounding area, rarely distant metastasis

• Often recurs after excision

Tumor components:

• Two basic tumor components:

• Tumor parenchyma: Tumor cells, the component that determines the name of the tumor.

• Tumor stroma: Connective tissue, blood vessels, lymph, supporting the tumor parenchyma and nourishing the tumor cells.

• One type of tumor that does not have a stroma: Leukemia (blood cancer).

Tumor nomenclature:

• Benign tumor from mesenchyme: Cell type name + oma

• Fibroma: Fibrous tumor

• Lipoma: Fatty tumor

• Chondroma: Cartilage tumor

• Osteoma: Bone tumor

• Hemangioma: Blood vessel tumor

• Lymphangioma: Lymph vessel tumor

• Leiomyoma: Smooth muscle tumor

• Rhabdomyoma: Striated muscle tumor

• Benign tumor from epithelium: Cell type name + oma

• Adenoma: Glandular tumor

• Cystadenoma: Cystic glandular tumor

• Papilloma: Papillary tumor

• Squamous papilloma: Skin papilloma

• Malignant tumor from mesenchyme: Cell type name + sarcoma

• Fibrosarcoma: Fibrous sarcoma

• Liposarcoma: Fatty sarcoma

• Chondrosarcoma: Cartilage sarcoma

• Osteosarcoma: Bone sarcoma

• Hemagiosarcoma: Blood vessel sarcoma

• Lymphangiosarcoma: Lymph vessel sarcoma

• Leiomyosarcoma: Smooth muscle sarcoma

• Rhabdomyosarcom: Striated muscle sarcoma

• Malignant tumor from epithelium: Cell type name + carcinoma

• Adenocarcinoma: Glandular carcinoma

• Cystandenocarcinoma: Cystic glandular carcinoma

• Squamous cell carcinoma: Squamous cell carcinoma

• Basal cell carcinoma: Basal cell carcinoma

• Urothelial carcinoma: Urothelial carcinoma

• Hepatocellular carcinoma: Hepatocellular carcinoma

• Other types of tumors:

• Pleomorphic adenoma, mixed tumor: Pleomorphic adenoma

• Teratoma: Germ cell tumor (benign/malignant/borderline malignant)

• Melanoma: Melanoma

• Lymphoma: Lymphoma

• Ewing’s sarcoma, Wilms’ tumor: (no detailed description)

• Fibroadenoma: Benign fibroadenoma

• Adenofibroma: Benign glandular fibrous tumor

• Adenomyoma: Benign glandular smooth muscle tumor

• Adenosarcoma: Tumor with benign epithelial and malignant mesenchymal components

• Carcinosarcoma: Tumor with malignant epithelial and mesenchymal components

• Seminoma, Dysgerminoma, Yolk sac tumor: Malignant germ cell tumors

• Seminoma: Seminoma in the testis

• Dysgerminoma: Dysgerminoma in the ovary

• Yolk sac tumor: Yolk sac tumor

Gross observation:

• Need to describe:

• Shape

• Size

• Boundaries

• Capsule

• Density

• Cut surface

• Some common gross forms of benign tumors:

• Protrusion

• Polyp

• Papillary

• Some common gross forms of malignant tumors:

• Exophytic mass

• Ulcer

• Hard infiltration

• Gross description of benign tumor:

• Well-defined boundaries, encapsulated, small size, slow growth, homogenous cut surface, firm density.

• Gross description of malignant tumor:

• No clear boundaries, infiltrating surrounding tissue, no capsule, large size, fast growth, heterogeneous cut surface with many areas of necrosis and hemorrhage, soft density.

Microscopic observation:

• Microscopic description of benign tumor:

• Well-differentiated in terms of structure and function (similar to normal tissue of origin)

• Mitotic figures +/-

• No invasion of surrounding tissue

• Microscopic description of malignant tumor:

• Decreased differentiation in structure and function

• Invasion of surrounding tissue

• Decreased differentiation includes:

• Increased cell density, disordered orientation

• Cellular and nuclear pleomorphism

• Hyperchromatic nuclei, deformed nuclei, large nucleoli, increased N/C ratio

• Increased mitotic figures, abnormal mitotic figures

• Cytoplasm containing normal or abnormal products

• Signs of malignancy: Abnormal mitotic figures

Histologic grading:

• Purpose: Assess the degree of malignancy

• Based on: Degree of differentiation, degree of atypia, necrosis, mitotic index

Natural progression of cancer:

• Four stages:

• Malignant transformation (monoclonal)

• Tumor growth

• Local invasion

• Metastasis

Difference between tumor cells and cells of reactive hyperplastic tissue:

• Tumor cells: Arising from a single initial cell => monoclonal.

• Cells of reactive hyperplastic tissue: Originating from many different cells => polyclonal.

Role of determining monoclonal nature:

• Distinguish between hyperplastic lymph nodes and tumors.

Hayflick limit:

• The limit on the number of divisions of normal cells, corresponding to cell aging.

• Tumor cells are not affected by the Hayflick limit.

• Tumor cells are immortal due to their ability to regenerate lost telomere segments through the activity of telomerase.

Note:

• The article has been rewritten from the given data, but it may still be incomplete or inaccurate.

• Consult additional specialized literature for a more comprehensive view of tumor pathology.