8.2 Human Anatomy & Physiology for Registrars: Tissues, Organ Walls, Subsites & Lymphatic Drainage
Key Takeaways
Carcinomas arise from epithelium (squamous, glandular or urothelial), sarcomas from connective tissue, and lymphomas and leukemias from blood-forming and lymphoid cells.
Hollow digestive organs have four main layers (mucosa, submucosa, muscularis propria, and serosa or adventitia); the deepest layer a tumor invades usually sets the T category.
The right lung has three lobes (upper, middle, lower) and the left lung two (upper, including the lingula, and lower); the colon runs cecum, ascending, hepatic flexure, transverse, splenic flexure, descending, sigmoid, then rectosigmoid junction and rectum.
Regional lymph nodes are defined for each site: breast drains mainly to axillary nodes, colon to pericolic and mesenteric nodes, lung to intrapulmonary, hilar and mediastinal nodes, and prostate and bladder to pelvic nodes.
Paired organs such as the breasts, lungs, kidneys, ovaries and testes require laterality coding, and bilateral tumors must go through the multiple primary rules.
Why anatomy is a separate blueprint topic
"Human anatomy and physiology" is one of the most highly rated knowledge statements in NCRA's 2022 role delineation study, and Route 3 candidates must have completed two semesters of it. On the exam, anatomy rarely appears as "name this bone." Instead it appears inside coding questions: which subsite, which wall layer, which node group is regional, and which organs are paired.
Levels of organization and tissue types
Cells form tissues, tissues form organs, and organs form systems. The four basic tissues map directly onto cancer categories:
| Tissue | Examples | Cancer family |
|---|---|---|
| Epithelial (lining and glandular) | Skin, lining of the GI tract, airways and ducts; glands | Carcinoma: squamous cell carcinoma from flat squamous epithelium, adenocarcinoma from glandular epithelium, urothelial carcinoma from the transitional lining of the urinary tract |
| Connective | Bone, cartilage, fat, fibrous tissue, blood vessels | Sarcoma (osteo-, chondro-, lipo-, fibro-, angio-) |
| Muscle | Smooth (organ walls), skeletal, cardiac | Leiomyosarcoma, rhabdomyosarcoma |
| Nervous | Neurons, glial cells, nerve sheaths | Gliomas (astrocytoma, glioblastoma), neuroblastoma, nerve sheath tumors |
Blood-forming tissue in the bone marrow produces two lineages. The myeloid lineage gives rise to red cells, platelets, granulocytes and monocytes, so its cancers include AML, CML, MDS and MPN. The lymphoid lineage produces B, T and NK cells, so its cancers include lymphomas, lymphoid leukemias and plasma cell neoplasms. This lineage split underlies the Hematopoietic Manual (Section 14.4).
The wall of a hollow organ
Hollow organs of the digestive tract share a layered wall:
- Mucosa: the epithelium, the lamina propria (supporting connective tissue) and the muscularis mucosae (a thin muscle layer).
- Submucosa: connective tissue rich in blood vessels and lymphatics.
- Muscularis propria: the main muscle coat, with inner circular and outer longitudinal layers.
- Subserosa and serosa (the visceral peritoneum) where the organ is covered by peritoneum; adventitia where it is not, as in the thoracic esophagus and part of the rectum.
In colorectal cancer, Tis is confined to the mucosa, T1 invades the submucosa, T2 the muscularis propria, T3 the pericolorectal tissue through the muscularis propria, T4a the visceral peritoneum, and T4b adjacent organs. The bladder wall (urothelium, lamina propria, muscularis propria, perivesical fat) follows the same idea for Ta, T1, T2 and T3 (Section 15.5).
Key organ subsites
| Organ | Subsites and landmarks | Coding notes |
|---|---|---|
| Colon and rectum | Cecum (C18.0), appendix (C18.1), ascending (C18.2), hepatic flexure (C18.3), transverse (C18.4), splenic flexure (C18.5), descending (C18.6), sigmoid (C18.7); rectosigmoid junction (C19.9); rectum (C20.9) | Endoscopic distance from the anal verge helps locate rectal and sigmoid tumors; the operation performed (for example, right hemicolectomy or low anterior resection) supports the site |
| Lung | Main bronchus (C34.0), upper lobe (C34.1), middle lobe (C34.2, right lung only), lower lobe (C34.3) | Right lung has 3 lobes; left lung has 2 (the lingula is part of the left upper lobe) |
| Breast | Nipple (C50.0), central (C50.1), upper-inner (C50.2), lower-inner (C50.3), upper-outer (C50.4), lower-outer (C50.5), axillary tail (C50.6) | Clock positions map to quadrants differently for the right and left breast; 12, 3, 6 and 9 o'clock lie on quadrant boundaries |
| Prostate | Peripheral, transition and central zones; right and left sides | Most adenocarcinomas arise in the peripheral zone, which lies next to the rectum and can be felt on digital rectal exam |
| Kidney | Cortex and medulla (parenchyma, C64.9); renal pelvis (C65.9); Gerota's fascia around the kidney and perirenal fat | Renal pelvis tumors are usually urothelial and are coded and staged separately from kidney parenchyma tumors |
| Bladder | Trigone, dome, lateral, anterior and posterior walls, bladder neck, ureteric orifice, urachus (C67.0–C67.9) | Multiple bladder subsites involved by one tumor use the overlapping code (C67.8) |
| Male genital | Testis (C62), epididymis (C63.0), spermatic cord (C63.1), penis (C60), prostate (C61.9), seminal vesicle (C63.7) | The testis is paired; cryptorchid (undescended) testis has its own subsite code |
Lymphatic drainage and regional lymph nodes
Lymph from each organ drains to predictable node groups, and AJCC and Summary Stage define which of them are regional for each site. Nodes outside that list are distant (M1).
| Primary site | Regional nodes (examples) | Commonly distant |
|---|---|---|
| Breast | Ipsilateral axillary (levels I–III), internal mammary, supraclavicular | Contralateral axillary or internal mammary, cervical |
| Colon | Pericolic, along the named colic vessels, mesenteric | Para-aortic, distant nodes |
| Lung | Intrapulmonary, hilar (N1); ipsilateral mediastinal and subcarinal (N2); contralateral mediastinal or hilar, scalene, supraclavicular (N3) | Nodes outside the thorax |
| Prostate | Pelvic: hypogastric, obturator, internal and external iliac, sacral | Common iliac and higher (M1a) |
| Bladder | Perivesical, obturator, internal and external iliac, sacral (N1–N2); common iliac (N3) | Nodes above the common iliac |
| Testis | Retroperitoneal (para-aortic, interaortocaval, paracaval) | Pelvic and inguinal nodes may be regional only after scrotal or inguinal surgery; the rules are in the AJCC chapter |
Always check the chapter for the site. The same node group can be regional for one primary and distant for another.
Body cavities and serosal membranes
- The peritoneum lines the abdominal cavity, pleura covers the lungs and pericardium surrounds the heart.
- Malignant cells in pleural or peritoneal fluid often mean distant (M1) disease. How to code this is site-specific; for example, a malignant pleural effusion is M1a in lung cancer.
- Retroperitoneal organs include the kidneys, adrenal glands, pancreas (mostly), the ascending and descending colon (partly) and the great vessels.
Physiology that shows up in abstracts
- Hormone dependence: estrogen and progesterone drive many breast cancers (the basis of ER and PR testing and endocrine therapy), and androgens drive prostate cancer (the basis of androgen deprivation therapy).
- Endocrine feedback: thyroid-stimulating hormone (TSH) stimulates thyroid cells, so suppressing it with thyroid hormone is recorded as hormone therapy for papillary and follicular thyroid cancer.
- Tumor markers reflect tissue physiology: PSA from prostate epithelium, AFP and beta-hCG from germ cell tumors, CEA from gut epithelium.
Paired organs and laterality
Paired sites listed in STORE include the parotid and submandibular glands, tonsils, lungs, pleura, breasts, ovaries, fallopian tubes, testes, epididymides, kidneys, renal pelves, ureters, eyes, adrenal glands and the cerebral hemispheres, among others. Record Laterality for each. Bilateral tumors in paired organs are sent through the multiple primary rules. Laterality alone does not decide the number of primaries.
A colonoscopy report describes a mass "at the hepatic flexure," and the resection specimen confirms it. Which ICD-O topography code applies?
C18.2 Ascending colon
C18.3 Hepatic flexure of colon
C18.4 Transverse colon
C18.5 Splenic flexure of colon
A lung tumor is described as arising in the lingula. Which lobe and topography code should the registrar record?
Right middle lobe, C34.2
Left upper lobe, C34.1
Left middle lobe, C34.2
Left lower lobe, C34.3
Which statement about the four basic tissue types and the cancers arising from them is correct?
Sarcomas arise from glandular epithelium.
Carcinomas arise from connective tissue such as bone and fat.
Lymphomas arise from skeletal muscle.
Urothelial carcinoma arises from the transitional epithelium lining the renal pelvis, ureters and bladder.
Sections you finish are checked off in the contents.