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Follicular dendritic cell sarcoma
Follicular dendritic cell sarcoma (FDCS), formerly follicular dendritic cell tumor, is a rare mesenchymal-derived sarcoma of B-follicle stromal cells, mostly extranodal (79.4%), treated by complete surgical excision, with local recurrence in 28% and metastasis in 27%.
Follicular lymphoma
Follicular lymphoma (FL) is an indolent B-cell non-Hodgkin lymphoma with nodular growth, t(14;18) IGH::BCL2 in 85% of cases, median survival near 20 years, and risk of DLBCL transformation.
Follicular lymphoma grade 1
Follicular lymphoma grade 1 (ICD-O-3 9695/3, ICD-11 2A80.0) is the lowest-grade, indolent follicle center B-cell non-Hodgkin lymphoma, defined by 0–5 centroblasts per high-power field, t(14;18) in up to 90% of grades 1–2, and treatment as indolent disease.
Follicular lymphoma grade 2
Follicular lymphoma grade 2 (ICD-11 2A80.1) is an indolent germinal-center B-cell lymphoma with 6-15 centroblasts per high-power field, grouped with grade 1 as grade 1-2 FL and optional in WHO-HAEM5.
Follicular lymphoma grade 3
Follicular lymphoma grade 3 (FL3, grades 3A and 3B) is an aggressive subtype of follicular B-cell non-Hodgkin lymphoma with over 15 centroblasts per high-power field; grade 3B is treated like diffuse large B-cell lymphoma.
Follicular lymphoma in situ
Follicular lymphoma in situ, now in situ follicular B-cell neoplasm (ISFN), is an incidental t(14;18)-positive BCL2/CD10-strong colonization of germinal centers in reactive nodes, with low progression risk (about 5%).
Follicular phase
Follicular phase: first phase of the menstrual cycle, from the first day of menstruation to ovulation, when FSH matures ovarian follicles and one dominant follicle releases an egg; typically 10-17 days and the main source of cycle length variability.
Follicular unit extraction
Follicular unit extraction (FUE) is a hair transplantation technique that harvests intact follicular units through small punch incisions, avoiding the linear donor scar left by strip harvesting.
Folliculitis
Folliculitis is inflammation of hair follicles from infection (Staphylococcus aureus, Pseudomonas), Malassezia yeast, irritation, or drugs, causing itchy or painful pustules; treatment depends on cause, with weak antibiotic trial evidence.
Folliculotropic mycosis fungoides
Folliculotropic mycosis fungoides (follicular, pilotropic MF) is a WHO-EORTC-recognized variant of mycosis fungoides in which T cells infiltrate hair follicles, sparing the epidermis, favoring head and neck, with follicular mucinosis, eyebrow plaques, alopecia, and stage-dependent survival.
Follitropin alfa
Follitropin alfa, marketed as GONAL-f, is a recombinant form of human follicle-stimulating hormone used to stimulate ovarian follicle growth in fertility treatment and sperm production in men.
Follitropin beta
Follitropin beta (Puregon, Follistim AQ) is a recombinant human FSH made in CHO cells from a single vector, EU-licensed 1996, used for ovulation induction, IVF stimulation, and spermatogenesis induction.
Fomivirsen
Fomivirsen (Vitravene), the first FDA-approved antisense drug (1998), a 21-mer phosphorothioate oligonucleotide targeting CMV IE2 mRNA, given intravitreally for CMV retinitis in AIDS; withdrawn in Europe 2002 and the US 2006.
Fonadelpar
Fonadelpar (NPS-005, SJP-0035) is an investigational Senju Pharmaceutical small-molecule PPARδ agonist, phase 3 as 0.001% eye drops for dry eye disease (DELTA-1, NCT03527212); not approved, also trialed in conduct disorder.
Fondaparinux
Fondaparinux (Arixtra), first synthetic anticoagulant launched 2004, is a pentasaccharide factor Xa inhibitor given subcutaneously; OASIS-5 showed bleeding reduction versus enoxaparin, but it is contraindicated in severe renal impairment and not used alone for PCI.
Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico
Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, or Policlinico di Milano, a Milan hospital founded by Duke Francesco Sforza in 1456; Italy's top-ranked public research hospital, IRCCS since 1981.
Fontaine progeroid syndrome
Fontaine progeroid syndrome (FPS, OMIM 612289), formerly Gorlin-Chaudhry-Moss and Fontaine-Farriaux syndromes, is an ultra-rare autosomal dominant progeroid disorder caused by de novo SLC25A24 codon 217 variants, with 13 molecularly confirmed cases worldwide.
Fontan procedure
Fontan procedure: final palliative operation for single-ventricle congenital heart disease, connecting systemic venous return directly to the pulmonary arteries; staged after Norwood and Glenn, with venous hypertension and late liver, lymphatic, and thrombotic complications.
Fontan-associated liver disease
Fontan-associated liver disease (FALD), congestive hepatopathy after the Fontan operation for single ventricle heart disease; universal fibrosis, cirrhosis in about 21%, HCC risk, biopsy-based staging.
Fontanelle
Fontanelles (soft spots, fonticuli cranii) are the six membrane-covered gaps between skull bones in fetuses and infants, closing after birth; the anterior fontanelle closes around 4 to 26 months and signals raised pressure or dehydration when bulging or sunken.
Food
Food is any substance consumed to provide nutritional support and energy. Covers nutrition and WHO dietary guidance, food history, global hunger (645 million undernourished in 2025), food security monitoring, and the environmental impact of diets.
Food allergy
Food allergy: immune-based adverse reaction to food, IgE-mediated or non-IgE-mediated, affecting ~33 million Americans. Diagnosed by oral food challenge; prevented by early allergen introduction; treated with epinephrine, OIT, omalizumab.
Food and drink prohibitions
Food and drink prohibitions, or food taboos, are religious or cultural bans on specified foods, such as pork in Judaism and Islam, beef in Hinduism, and alcohol in Islam, with documented nutritional effects.
Food and Nutrition Service
Food and Nutrition Service (FNS), now the Food and Nutrition Administration (FNA), is the USDA agency, established August 8, 1969, administering 15 federal nutrition assistance programs including SNAP, WIC, and school meals.
Food effect study
A food effect study is a clinical pharmacology study measuring how food changes an oral drug's absorption and exposure, comparing fed and fasted dosing to support labeling.
Food energy
Food energy is metabolizable energy from food, measured in kcal or kJ and usually calculated with Atwater factors (4/9/4 kcal per g protein/carbohydrate/fat), which overestimate energy from intact plant foods like almonds.
Food fortification
Food fortification, also known as food enrichment or nutrification, is the deliberate addition of vitamins and minerals to foods, notably iodized salt since 1924, to improve public health.
Food frequency questionnaire
A food frequency questionnaire (FFQ) is a dietary survey asking how often, and in what portions, people ate listed foods over about a year, typically taking 10–20 minutes.
Food group
Food group: a category of foods with similar nutritional roles used in dietary guidance. U.S. history runs from the 1916 five-group guide through Basic Seven, Basic Four, the Food Guide Pyramid, MyPyramid, MyPlate, and the 2025-2030 inverted pyramid.
Food hygiene
Food hygiene: all conditions and measures ensuring food safety and suitability across the food chain, per Codex. Covers HACCP controls, contamination prevention, the 1963 Codex Alimentarius, and WHO's estimate of 866 million annual foodborne illness cases.