Tumors and Cancers

Endocrine Glands – Blood – Marrow – Lymph

Dongyou Liu

• Editorial: CRC Press
• Año: 2017
• ISBN:
  9781351646864
• Edición: 1
• Categoría: Medizin
• Categoría: Onkologie

Tumors and Cancers: Endocrine Glands – Blood – Marrow – Lymph provides succinct reviews of neoplastic growths disrupting normal functions of affected structures. Each chapter presents a state of the art summary of tumor/cancer of a particular type in relation to its biology, epidemiology, disease mechanisms, clinical signs, diagnosis, treatment and prognosis.

1

Introductory Remarks

1.1 Preamble

Tumor or cancer (these terms, along with neoplasm and lesion, are used interchangeably in colloquial language and publications; see Glossary) is an insidious disease that results from an uncontrolled growth of abnormal cells in part(s) of the body. Tumor/cancer has acquired a notorious reputation due not only to its ability to exploit host cellular machineries for its own advantages but also to its potential to cause human misery.

With a rapidly aging world population, widespread oncogenic viruses, and constant environmental pollution and destruction, tumor/cancer is poised to exert an increasingly severe toll on human health and well-being. There is a burgeoning interest from health professionals and the general public in learning about tumor/cancer mechanisms, clinical features, diagnosis, treatment, and prognosis. The following pages in the current volume as well as those in the sister volumes represent a concerted effort to satisfy this critical need.

1.2 Tumor mechanisms

The human body is composed of various types of cells that grow, divide, and die in an orderly fashion (a process known as apoptosis). However, when some cells in the body change their growth patterns and fail to undergo apoptosis, they often produce a solid tumor or sometimes a nonsolid tumor (e.g., leukemia). A tumor is considered benign if it grows but does not spread beyond the immediate area in which it arises. While most benign tumors are not life-threatening, those found in the vital organs (e.g., the brain) can be deadly. In addition, some benign tumors are precancerous, with the propensity to become cancerous if left untreated. On the contrary, a tumor is considered malignant and cancerous if it grows continuously and spreads to surrounding areas and other parts of the body through the blood or lymph system.

A tumor located in its original (primary) site is known as a “primary tumor.” A tumor that spreads from its original (primary) site via the neighboring tissue, bloodstream, or lymphatic system to another site in the body is called a “metastatic tumor/cancer” (or secondary tumor/cancer). A metastatic cancer has the same name and the same type of cancer cells as a primary cancer. For instance, a metastatic cancer in the brain that originates from breast cancer is known as metastatic breast cancer—not brain cancer.

Typically, tumors/cancers form in tissues after the cells undergo genetic mutations that lead to sequential changes known as hyperplasia, metaplasia, dysplasia, neoplasia, and anaplasia (see Glossary). Factors contributing to genetic mutations in the cells may be chemical (e.g., cigarette smoking, asbestos, paint, dye, bitumen, mineral oil, nickel, arsenic, aflatoxin, and wood dust), physical (e.g., sun, heat, radiation, and chronic trauma), viral (e.g., EBV, HBV, HPV, and HTLV-1), immunological (e.g., AIDS and transplantation), endocrine (e.g., excessive endogenous or exogenous hormones), or hereditary (e.g., familial inherited or non-inherited disorders).

In essence, tumorigenesis is a cumulative process that demonstrates several notable hallmarks, including (i) sustaining proliferative signaling, (ii) activating local invasion and metastasis, (iii) resisting apoptosis and enabling replicative immortality, (iv) inducing angiogenesis and inflammation, (v) evading immune destruction, (vi) deregulating cellular energetics, and (vii) genome instability and mutation.

1.3 Tumor classification, grading, and staging

A tumor/cancer is usually named for the organs or tissues where it starts (e.g., brain cancer, breast cancer, lung cancer, lymphoma, and skin cancer). Depending on the types of tissue involved, tumors/cancers are grouped into a number of broad categories: (i) carcinoma (involving epithelium), (ii) sarcoma (involving soft tissue), (iii) leukemia (involving blood-forming tissue), (iv) lymphoma (involving lymphocytes), (v) myeloma (involving plasma cells), (vi) melanoma (involving melanocytes), (vii) central nervous system cancers (involving brain or spinal cord), (viii) germ cell tumors (involving cells that give rise to sperm or eggs), (ix) neuroendocrine tumors (involving hormone-releasing cells), and (x) carcinoid tumors (a variant of neuroendocrine tumors found mainly in the intestinal tract).

Primary tumors of the endocrine system include those affecting the adrenal, pituitary, parathyroid, and thyroid glands as well as the endocrine pancreas. In addition, inherited and non-inherited tumor syndromes (e.g., Carney complex; Li–Fraumeni syndrome; Mahvash disease; McCune–Albright syndrome; multiple endocrine neoplasia types 1, 2, and 4; von Hippel–Lindau syndrome [VHL]; neurofibromatosis type 1; hyperparathyroidism-jaw tumor syndrome; familial paraganglioma–pheochromocytoma syndrome; and familial non-medullary thyroid cancer) are known to predispose the endocrine glands and other organs to a range of neoplasms [1].

Tumors of the hematopoietic and lymphoreticular systems consist of two main categories: (i) myeloid neoplasms and acute leukemias (which account for about 35% of all hematopoietic and lymphoreticular neoplasms) and (ii) mature lymphoid, histiocytic, and dendritic neoplasms (which include myeloma and represent 65% of all hematopoietic and lymphoreticular neoplasms) [2–5].

Myeloid neoplasms and acute leukemias are further separated into 10 groups: (i) myeloproliferative neoplasms (MPN), (ii) mastocytosis, (iii) myeloid/lymphoid neoplasms with eosinophilia and rearrangements, (iv) myelodysplastic/myeloproliferative neoplasms (MDS/MPN), (v) myelodysplastic syndrome (MDS), (vi) acute myeloid leukemia (AML), (vii) blastic plasmacytoid dendritic cell neoplasms (BPDCN) (viii) acute leukemia of ambiguous lineage (ALAL), (ix) B-lymphoblastic leukemia/lymphoma, and (x) T-lymphoblastic leukemia/lymphoma [4].

Similarly, mature lymphoid, histiocytic, and dendritic neoplasms are subdivided into five groups: (i) mature B-cell neoplasms, (ii) mature T and NK neoplasms, (iii) Hodgkin lymphoma, (iv) posttransplant lymphoproliferative disorders (PTLD), and (v) histiocytic and dendritic cell neoplasms. Of these, mature B-cell neoplasms and mature T and NK neoplasms are commonly referred to as non-Hodgkin lymphoma (NHL) [5].

Under the auspices of the World Health Organization (WHO), the International Classification of Diseases for Oncology, third edition (ICD-O-3) [6], has designed a five-digit system for classifying tumors, with the first four digits being the morphology code and the fifth digit being the behavior code [6]. The fifth digit behavior codes for neoplasms range from 0 (benign), 1 (benign or malignant), 2 (carcinoma in situ), 3 (malignant, primary site), 6 (malignant, metastatic site) to 9 (malignant, primary or metastatic site). For example, chondroma has an IDC-O-3 code of 9220/0 and is considered a benign bone tumor; multiple chondromatosis (a subtype of chondroma) has an IDC-O-3 code of 9220/1 and is an intermediate grade bone tumor with the potential for malignant transformation; and central chondrosarcoma has an IDC-O-3 code of 9220/3 and is considered a malignant bone tumor [6].

To further delineate tumors/cancers and assist in their treatment and prognosis, the pathological stages of solid tumors are often determined by using the TNM system (see Glossary) of the American Joint Commission on Cancer (AJCC), which incorporates the size and extent of the primary tumor (TX, T0, T1, T2, T3, T4), the number of nearby lymph nodes involved (NX, N0, N1, N2, N3), and the presence of distant metastasis (MX, M0, M1) [7]. Therefore, under the TNM system, the pathological stage of a given tumor or cancer may be referred to as T1N0MX or T3N1M0 (with numbers after each letter providing further details about the tumor or cancer). However, a much more simplified staging system (0, I, II, III, IV) is adopted clinically to describe the stages of solid tumors (see “stage” in Glossary) [7].

Another staging system that is more often used by cancer registries than by doctors divides tumors/cancers into five categories: (i) in situ (abnormal cells are present but have not spread to nearby tissue); (ii) localized (cancer is limited to the place where it started, with no sign that it has spread); (iii) regional (cancer has spread to nearby lymph nodes, tissues, or organs); (iv) distant (cancer has spread to distant parts of the body); and (v) unknown (there is not enough information to determine the stage).

1.4 Tumor diagnosis

As most tumors/cancers tend to induce nonspecific, noncharacteristic clinical signs, a variety of procedures and tests are utilized during a diagnostic workup. These involve a medical history review of the patient and their relatives (for clues to potential risk factors that enhance cancer development), a complete physiological examination (for lumps and other abnormalities), imaging techniques (e.g., ultrasound, CT, MRI, and PET; see Glossary), biochemical and immunological tests (for altered substance or cell levels in blood, bone marrow, cerebrospinal fluid, urine, and tissue), histological evaluation of biopsy and tissue (using hematoxylin and eosin [H&E] and immunohistochemical [IHC] stains; see Glossary), and molecular analyses (e.g., FISH and PCR; see Glossary).

1.5 Tumor treatment and prognosis

Standard cancer treatments consist of surgery (for removal of tumors and relieving symptoms associated with tumors), radiotherapy (also called radiation therapy or X-ray therapy; delivered externally through the skin or internally [brachytherapy] for destruction of cancer cells or impeding their growth), chemotherapy (for inhibiting the growth of cancer cells, suppressing the body’s hormone production, blocking the effect of the hormone on cancer cells, etc.—usually via the bloodstream or oral ingestion), and complementary therapies (for enhancing patients’ quality of life and improving their well-being). Depending on the circumstances, surgery may be used in combination with radiotherapy and/or chemotherapy to ensure that any cancer cells remaining in the body are eliminated.

The outcomes of tumor/cancer treatments include (i) cure (no traces of cancer remain after treatment, and the cancer will never come back), (ii) remission (signs and symptoms of cancer are reduced; in a complete remission, all signs and symptoms of cancer disappearing for 5 years or more suggest a cure), or (iii) recurrence (a benign or cancerous tumor comes back after surgical removal and adjunctive therapy).

Prognosis (or chance of recovery) for a given tumor/cancer is usually dependent on the location, type, and grade of the tumor, patient’s age and health status, etc. Regardless of tumor/cancer types, patients with lower grade lesions generally have a better prognosis than those with higher grade lesions.

1.6 Future perspective

Tumor/cancer is a biologically complex disease that is expected to surpass heart disease to become the leading cause of human death throughout the world in the coming decades. Despite extensive past research and development efforts, tumor/cancer remains poorly understood, and effective cures remain largely elusive.

The completion of the Human Genome Project in 2003 and the establishment of The Cancer Genome Atlas (TCGA) in 2005 have offered promises for better understanding of the genetic basis of human tumors/cancers and have opened new avenues for developing novel diagnostic techniques and effective therapeutic measures.

Nonetheless, a multitude of factors pose continuing challenges for the ultimate conquest of tumors/cancers. These include the inherent biological complexity and heterogeneity of tumors/cancers, contribution of various genetic and environmental risk factors, absence of suitable models for human tumors/cancers, and difficulty in identifying therapeutic compounds that kill/inhibit cancer cells only and not normal cells. Further efforts are necessary to help overcome these obstacles and to enhance the well-being of cancer sufferers.

Acknowledgments

Credit is due to a group of international oncologists/clinicians whose expert contributions have greatly enriched this volume.

References

1. DeLellis RA. (ed). Pathology and genetics of tumours of endocrine organs. International Agency for Research on Cancer; World Health Organization; International Academy of Pathology; International Association for the Study of Lung Cancer. Lyon: IARC Press, 2004.

2. Jaffe ES, Harris NL, Stein H, Vardiman JW. Pathology and genetics of tumours of haematopoietic and lymphoid tissues; World Health Organization; Lyon: IARC Press; Oxford University Press (distributor), 2001.

3. Swerdlow SH, Campo E, Harris NL, et al. (eds). WHO classification of tumours of haematopoietic and lymphoid tissues. International Agency for Research on Cancer; World Health Organization. Lyon, France: IARC, 2008.

4. Arber DA, Orazi A, Hasserjian R, et al. The 2016 revision to the World Health Organization classification of myeloid neopla...