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Liver: Non-Neoplastic Diseases

Normal Anatomy Several structural and functional units have been proposed in the microanatomy of the liver. Of these, the most relevant for the diagnostic histopathologist are the liver lobule and the liver acinus. For several years the liver acinus was the preferred concept in textbooks of pathology and hepatology, as it appeared to better explain the “bridging” type of lesions connecting afferent and efferent vascular landmarks,…

Anus

Normal Anatomy of the Anus The anus and anal canal comprise a complex anatomic region with historically controversial nomenclature, due to the fact that the extent of the zones from person to person is variable and that the macroscopic and microscopic zones often do not correspond. The anal canal is a tubular structure measuring 3–4 cm in length and includes the squamous zone, the transition zone, and…

Large Bowel

Normal Anatomy of the Large Bowel The large bowel comprises the terminal 1–1.5 m of the gastrointestinal tract and is divided into the following regions: cecum, ascending (right) colon, transverse colon, descending (left) colon, sigmoid colon, and rectum. The hepatic flexure is at the junction of the ascending and transverse colon, and the splenic flexure is at the junction of the transverse and descending colon. The rectum…

Appendix

Normal Anatomy of the Appendix The vermiform appendix is a tubular structure arising from the medial wall of the cecum; it averages 9 cm in length and 0.7 cm in greatest diameter, although the luminal dimensions may vary along the length of the organ. Despite ongoing speculation and debate, vermiform appendix has no known function in humans and is typically regarded as a vestigial organ. The appendix reaches…

Small Bowel

Normal Anatomy The small bowel extends from the pylorus to the ileocecal valve and measures approximately 6–7 m in length in adults. It is divided into three portions: duodenum , jejunum , and ileum . The ligament of Treitz is the anatomic landmark for the duodenojejunal junction, at which site the bowel becomes unfixed and wrapped in mesentery. The inner side of the small bowel is characterized…

Stomach

Normal Anatomy The stomach is divided into the following regions: cardia , fundus , corpus or body , antrum , and pylorus . The superomedial margin is termed the lesser curvature , and the inferolateral margin is termed the greater curvature . The junction between the corpus and the antrum is marked on the serosal side by a notch in the lesser curvature known as the…

Esophagus

Normal Anatomy of the Esophagus The esophagus is a muscular tubular structure that measures approximately 25 cm in adult individuals and extends from the cricopharyngeal muscle, which forms the upper esophageal sphincter (at the level of the sixth cervical vertebra, about 15–18 cm from the incisors), to the lower esophageal sphincter, which forms the gastroesophageal junction (GEJ; several centimeters below the diaphragm). The lower esophageal sphincter is usually…

Mediastinum

Generalities The mediastinum is the portion of the thoracic cavity located between the pleural cavities, extending anteroposteriorly from the sternum to the spine and from the thoracic inlet superiorly to the diaphragm inferiorly. The numerous organs and structures it contains make it a veritable Pandora's box, within which congenital cysts, benign tumors, and primary and metastatic neoplasms may develop. An arbitrary division of the mediastinum into…

Pleura

Normal Anatomy of the Pleura Both the visceral and parietal pleural layers have a lining of mesothelial cells endowed with a continuous basement membrane and resting on a layer of well-vascularized fibroelastic connective tissue matrix. The submesothelial connective tissue is divided by superficial and deep elastic lamina. All of these elements are mesodermally derived. The normal mesothelial cell is flat or low cuboidal. Ultrastructurally, it features…

Lung

Normal Anatomy Grossly the lungs are subdivided into lobes, three on the right (upper, middle, and lower) and two on the left (upper and lower). Each lobe is supplied by a dedicated lobar bronchus with a companion artery and vein that subdivides into bronchopulmonary segments. Bronchopulmonary segments are of special importance to thoracic surgeons because they are amenable to surgical excision in those patients for whom…

Parathyroid Glands

Normal Gross Anatomy and Embryology The parathyroid glands, the last major organ to be recognized in humans, were discovered in 1880 by Ivar Sandstrom, a Swedish medical student, as recounted by Aidan Carney in his delightful essay on the subject. Normally, there are four oval, pliable parathyroid glands, each averaging 4 × 3 × 1.5 mm. In rare cases, more than four glands are present. In their…

Thyroid Gland

Normal Anatomy and Thyroid Gland Development The thyroid anlage appears in the embryo as a midline structure at the site corresponding to the foramen cecum of the adult tongue. From here, it descends as a component of the thyroglossal duct along the midline to reach its final position in the mid neck. Later, the hyoid bone is formed from the second branchial arch. The thyroglossal duct…

Ear

Introduction Nearly all the diseases that can involve the ear also occur in other sites of the body. However, some of these diseases either have a predilection for the ear or pose special problems when occurring at this site. Only the features of these lesions as they pertain to their location in the ear will be discussed here. The general features of the various entities are…

Major and Minor Salivary Glands

Normal Anatomy The major salivary glands are the paired parotid, submandibular (submaxillary), and sublingual glands. The parotid gland weighs 14–28 g, the submandibular gland weighs 7–8 g, and the sublingual gland weighs 3 g. The main duct of the parotid gland (Stensen duct) empties into the oral cavity opposite the crown of the second maxillary molar. The main ducts of both the submandibular glands (Wharton duct) and sublingual glands…

Mandible and Maxilla

Normal Anatomy In most respects, the microscopic features of the mandible and maxilla differ in no significant way from those of any other bones. Their peculiarity is derived from their close proximity to the mucosal surface of the oral cavity and the fact that they enclose the odontogenic apparatus, a highly specialized structure that gives rise to a large variety of malformative, inflammatory, and neoplastic conditions.…

Upper Aerodigestive Tract

Oral Cavity and Oropharynx Normal Anatomy The oral cavity and oropharyngeal region represent the upper portion of the digestive tract; in addition, the oropharynx constitutes a portion of the upper respiratory tract. The oropharynx and hypopharynx share many of the diseases of the two adjacent digestive tract organs—oral cavity and esophagus—whereas the nasopharynx shares them with the two other components of the upper respiratory tract, that…

Tumors and Tumorlike Conditions of the Skin

The skin is, contrary to the ubiquitous simplistic concept, a remarkably heterogeneous organ. The nodular lesions (hamartomatous, reactive, and neoplastic) that occur in the skin are more numerous than those produced by any other organ. For example, the eccrine sweat gland alone gives rise to 10 or more histologically distinct adenomas. This diversity, combined with a body of descriptive data (clinical, histologic, histochemical, immunohistochemical, and ultrastructural)…

Dermatoses

Introduction to Dermatopathology The entities described in this section are a select group taken from the large number of diseases that affect the skin. They have been chosen to encompass the types of non-neoplastic material generally seen in surgical pathology laboratories. Many of the infrequently biopsied, histologically nonspecific, and rare dermatoses are excluded. Their characteristics are described in texts devoted wholly to dermatopathology and in the…

Skin

The contributions to this chapter by Dr. Alexander J. Lazar, Department of Pathology, MD Anderson Cancer Center, Houston, Texas, in several previous editions of this book are gratefully acknowledged. Skin disorders are common and diverse, ranging from irritating itching to life-threatening melanoma. Many of these conditions are confined to the skin, but others are manifestations of multiorgan diseases, such as systemic lupus erythematosus or neurofibromatosis. In…