to provide contrast. histochemistry refers to the science of using chemical reactions between laboratory chemicals and components within tissue. the histological slides are then interpreted diagnostically and the resulting pathology report describes the histological findings and the opinion of the pathologist. in the case of cancer, this represents the tissue diagnosis required for most treatment protocols. neuropathology main article: neuropathology this coronal cross-section of a brain reveals a significant arteriovenous malformation that occupies much of the parietal lobe. neuropathology is the study of disease of nervous system tissue, usually in the form of either surgical biopsies or sometimes whole brains in the case of autopsy. neuropathology is a subspecialty of anatomic pathology, neurology, and neurosurgery. in many english-speaking countries, neuropathology is considered a subfield of anatomical pathology. a physician who specializes in neuropathology, usually by completing a fellowship after a residency in anatomical or general pathology, is called a neuropathologist. in day-to-day clinical practice, a neuropathologist is a consultant for other physicians. if a disease of the nervous system is suspected, and the diagnosis cannot be made by less invasive methods, a biopsy of nervous tissue is taken from the brain or spinal cord to aid in diagnosis. biopsy is usually requested after a mass is detected by medical imaging. with autopsies, the principal work of the neuropathologist is to help in the post-mortem diagnosis of various conditions that affect the central nervous system. biopsies can also consist of the skin. epidermal nerve fiber density testing (enfd) is a more recently developed neuropathology test in which a punch skin biopsy is taken to identify small fiber neuropathies by analyzing the nerve fibers of the skin. this test is becoming available in select labs as well as many universities; it replaces the traditional nerve biopsy test as less invasive. pulmonary pathology main article: pulmonary pathology gross pathology of miliary tuberculosis of the lung. pulmonary pathology is a subspecialty of anatomic (and especially surgical) pathology that deals with diagnosis and characterization of neoplastic and non-neoplastic diseases of the lungs and thoracic pleura. diagnostic specimens are often obtained via bronchoscopic transbronchial biopsy, ct-guided percutaneous biopsy, or video-assisted thoracic surgery. these tests can be necessary to diagnose between infection, inflammation, or fibrotic conditions. renal pathology main article: renal pathology this tissue cross-section demonstrates the gross pathology of polycystic kidneys. renal pathology is a subspecialty of anatomic pathology that deals with the diagnosis and characterization of disease of the kidneys. in a medical setting, renal pathologists work closely with nephrologists and transplant surgeons, who typically obtain diagnostic specimens via percutaneous renal biopsy. the renal pathologist must synthesize findings from traditional microscope histology, electron microscopy, and immunofluorescence to obtain a definitive diagnosis. medical renal diseases may affect the glomerulus, the tubules and interstitium, the vessels, or a combination of these compartments. surgical pathology main article: surgical pathology brain biopsy under stereotaxy. a small part of the tumor is taken via a needle with a vacuum system. surgical pathology is one of the primary areas of practice for most anatomical pathologists. surgical pathology involves the gross and microscopic examination of surgical specimens, as well as biopsies submitted by surgeons and non-surgeons such as general internists, medical subspecialists, dermatologists, and interventional radiologists. often an excised tissue sample is the best and most definitive evidence of disease (or lack thereof) in cases where tissue is surgically removed from a patient. these determinations are usually accomplished by a combination of gross (i.e., macroscopic) and histologic (i.e., microscopic) examination of the tissue, and may involve evaluations of molecular properties of the tissue by immunohistochemistry or other laboratory tests. there are two major types of specimens submitted for surgical pathology analysis: biopsies and surgical resections. a biopsy is a small piece of tissue removed primarily for surgical pathology analysis, most often in order to render a definitive diagnosis. types of biopsies include core biopsies, which are obtained through the use of large-bore needles, sometimes under the guidance of radiological techniques such as ultrasound, ct scan, or magnetic resonance imaging. incisional biopsies are obtained through diagnostic surgical procedures that remove part of a suspicious lesion, whereas excisional biopsies remove the entire lesion, and are similar to therapeutic surgical resections. excisional biopsies of skin lesions and gastrointestinal polyps are very common. the pathologist's interpretation of a biopsy is critical to establishing the diagnosis of a benign or malignant tumor, and can differentiate between different types and grades of cancer, as well as determining the activity of specific molecular pathways in the tumor. surgical resection specimens are obtained by the therapeutic surgical removal of an entire diseased area or organ (and occasionally multiple organs). these procedures are often intended as definitive surgical treatment of a disease in which the diagnosis is already known or strongly suspected, but pathological analysis of these specimens remains important in confirming the previous diagnosis. clinical pathology main article: clinical pathology clinical pathology is a medical specialty that is concerned with the diagnosis of disease based on the laboratory analysis of bodily fluids such as blood and urine, as well as tissues, using the tools of chemistry, clinical microbiology, hematology and molecular pathology. clinical pathologists work in close collaboration with medical technologists, hospital administrations, and referring physicians. clinical pathologists learn to administer a number of visual and microscopic tests and an especially large variety of tests of the biophysical properties of tissue samples involving automated analysers and cultures. sometimes the general term "laboratory medicine specialist" is used to refer to those working in clinical pathology, including medical doctors, ph.d.s and doctors of pharmacology. immunopathology, the study of an organism's immune response to infection, is sometimes considered to fall within the domain of clinical pathology. hematopathology main article: hematopathology clinical chemistry: an automated blood chemistry analyzer hematopathology is the study of diseases of blood cells (including constituents such as white blood cells, red blood cells, and platelets) and the tissues, and organs comprising the hematopoietic system. the term hematopoietic system refers to tissues and organs that produce and/or primarily host hematopoietic cells and includes bone marrow, the lymph nodes, thymus, spleen, and other lymphoid tissues. in the united states, hematopathology is a board certified subspecialty (licensed under the american board of pathology) practiced by those physicians who have completed a general pathology residency (anatomic, clinical, or combined) and an additional year of fellowship training in hematology. the hematopathologist reviews biopsies of lymph nodes, bone marrows and other tissues involved by an infiltrate of cells of the hematopoietic system. in addition, the hematopathologist may be in charge of flow cytometric and/or molecular hematopathology studies. molecular pathology main article: molecular pathology molecular pathology is focused upon the study and diagnosis of disease through the examination of molecules within organs, tissues or bodily fluids. molecular pathology is multidisciplinary by nature and shares some aspects of practice with both anatomic pathology and clinical pathology, molecular biology, biochemistry, proteomics and genetics. it is often applied in a context that is as much scientific as directly medical and encompasses the development of molecular and genetic approaches to the diagnosis and classification of human diseases, the design and validation of predictive biomarkers for treatment response and disease progression, and the susceptibility of individuals of different genetic constitution to particular disorders. the crossover between molecular pathology and epidemiology is represented by a related field "molecular pathological epidemiology". molecular pathology is commonly used in diagnosis of cancer and infectious diseases. molecular pathology is primarily used to detect cancers such as melanoma, brainstem glioma, brain tumors as well as many other types of cancer and infectious diseases. techniques are numerous but include quantitative polymerase chain reaction (qpcr), multiplex pcr, dna microarray, in situ hybridization, dna sequencing, antibody-based immunofluorescence tissue assays, molecular profiling of pathogens, and analysis of bacterial genes for antimicrobial resistance. techniques used are based on analyzing samples of dna and rna. pathology is widely used for gene therapy and disease diagnosis. oral and maxillofacial pathology main article: oral and maxillofacial pathology many conditions, such as this case of geographic tongue, can be diagnosed partly on gross examination, but may be confirmed with tissue pathology. oral and maxillofacial pathology is one of nine dental specialties recognized by the american dental association, and is sometimes considered a specialty of both dentistry and pathology. oral pathologists must complete three years of post doctoral training in an accredited program and subsequently obtain diplomate status from the american board of oral and maxillofacial pathology. the specialty focuses on the diagnosis, clinical management and investigation of diseases that affect the oral cavity and surrounding maxillofacial structures including but not limited to odontogenic, infectious, epithelial, salivary gland, bone and soft tissue pathologies. it also significantly intersects with the field of dental pathology. although concerned with a broad variety of diseases of the oral cavity, they have roles distinct from otorhinolaryngologists ("ear, nose, and throat" specialists), and speech pathologists, the latter of which helps diagnose many neurological or neuromuscular conditions relevant to speech phonology or swallowing. owing to the availability of the oral cavity to non-invasive examination, many conditions in the study of oral disease can be diagnosed, or at least suspected, from gross examination, but biopsies, cell smears, and other tissue analysis remain important diagnostic tools in oral pathology. medical training and accreditation an anatomical pathology instructor uses a microscope with multiple eyepieces to instruct students in diagnostic microscopy. becoming a pathologist generally requires specialty-training after medical school, but individual nations vary some in the medical licensing required of pathologists. in the united states, pathologists are physicians (d.o. or m.d.) who have completed a four-year undergraduate program, four years of medical school training, and three to four years of postgraduate training in the form of a pathology residency. training may be within two primary specialties, as recognized by the american board of pathology: anatomical pathology and clinical pathology, each of which requires separate board certification. the american osteopathic board of pathology also recognizes four primary specialties: anatomic pathology, dermatopathology, forensic pathology, and laboratory medicine. pathologists may pursue specialised fellowship training within one or more subspecialties of either anatomical or clinical pathology. some of these subspecialties permit additional board certification, while others do not. in the united kingdom, pathologists are physicians licensed by the uk general medical council. the training to become a pathologist is under the oversight of the royal college of pathologists. after four to six years of undergraduate medical study, trainees proceed to a two-year foundation program. full-time training in histopathology currently lasts between five and five and a half years and includes specialist training in surgical pathology, cytopathology, and autopsy pathology. it is also possible to take a royal college of pathologists diploma in forensic pathology, dermatopathology, or cytopathology, recognising additional specialist training and expertise and to get specialist accreditation in forensic pathology, pediatric pathology, and neuropathology. all postgraduate medical training and education in the uk is overseen by the general medical council. in france, pathology is separated into two distinct specialties, anatomical pathology, and clinical pathology. residencies for both lasts four years. residency in anatomical pathology is open to physicians only, while clinical pathology is open to both physicians and pharmacists. at the end of the second year of clinical pathology residency, residents can choose between general clinical pathology and a specialization in one of the disciplines, but they can not practice anatomical pathology, nor can anatomical pathology residents practice clinical pathology. overlap with other diagnostic medicine main articles: diagnostic medicine, oncology, infectious disease, and medical imaging though separate fields in terms of medical practice, a number of areas of inquiry in medicine and medical science either overlap greatly with general pathology, work in tandem with it, or contribute significantly to the understanding of the pathology of a given disease or its course in an individual. as a significant portion of all general pathology practice is concerned with cancer, the practice of oncology makes extensive use of both anatomical and clinical pathology in diagnosis and treatment. in particular, biopsy, resection, and blood tests are all examples of pathology work that is essential for the diagnoses of many kinds of cancer and for the staging of cancerous masses. in a similar fashion, the tissue and blood analysis techniques of general pathology are of central significance to the investigation of serious infectious disease and as such inform significantly upon the fields of epidemiology,