PA7.1,PA22.1-5 | Diagnostic Cytology & Clinical Pathology — Glossary

The most common cause of intrinsic AKI; results from ischaemia or nephrotoxins injuring the tubular epithelium; urine Na⁺ > 40 mmol/L, FENa > 2%, granular casts in urine sediment.

An enzyme elevated in TB effusions and TB meningitis due to T-lymphocyte activity; CSF ADA >10 U/L and pleural fluid ADA >40 U/L support a diagnosis of TB.

Enzyme elevated in cholestatic liver disease and bone disorders; liver isoform confirmed by concurrent elevation of GGT; placental and intestinal isoforms also exist.

Cytosolic liver enzyme released into blood during hepatocyte injury; more liver-specific than AST; the primary marker of hepatocellular necrosis.

Autoantibodies against thyroid peroxidase, the enzyme catalysing thyroid hormone synthesis; elevated in Hashimoto's thyroiditis (~90%) and Graves' disease (~75%).

A discriminatory index in liver disease: ratio > 2:1 is strongly associated with alcoholic liver disease (mitochondrial AST preferentially released); ratio < 1 suggests viral or metabolic hepatitis.

Reduced sperm motility: total motility < 42% or progressive motility < 30% of spermatozoa; affects sperm's ability to traverse the female reproductive tract.

Complete absence of spermatozoa in the ejaculate after centrifugation; confirmed on two separate samples. Classified as obstructive (ductal block, normal spermatogenesis) or non-obstructive (primary testicular failure).

Negative for Intraepithelial Lesion or Malignancy — the Bethesda category for a normal or benign cervical smear; does not mean zero cancer risk, but indicates no cytological abnormality detected.

Standardised reporting terminology for cervical cytology (2014) classifying findings into NILM, ASCUS, LSIL, HSIL, or carcinoma; a separate Bethesda system exists for thyroid FNAC (BSRTC).

A rhomboid-shaped, positively birefringent crystal found in pseudogout (chondrocalcinosis); appears blue when parallel to the slow axis of the compensator.

Preparation made from centrifuged pellet of cell-rich fluid fixed in formalin and processed as a paraffin block; allows immunohistochemistry on cytological material.

Water-soluble bilirubin that has been processed by hepatocytes (glucuronide conjugation); elevated in hepatic and posthepatic jaundice; appears in urine (dark urine).

An autosomal recessive disorder of renal tubular transport of dibasic amino acids (COAL: Cystine, Ornithine, Arginine, Lysine), causing recurrent urolithiasis and hexagonal urine crystals.

Branch of pathology examining individual cells or small cell clusters on smears; complements histopathology but cannot assess tissue architecture.

A colorimetric multi-pad strip that simultaneously screens urine for pH, protein, glucose, ketones, blood, bilirubin, urobilinogen, nitrites, and leucocyte esterase.

Premature keratin production in individual malignant squamous cells before they reach the surface; seen in squamous cell carcinoma cytology as dense orange cytoplasm on Pap stain.

Morphologically distorted red blood cells with irregular blebs and protrusions resulting from passage through a damaged glomerular filtration barrier; their presence indicates glomerular haematuria.

Calculated index of kidney filtration function derived from serum creatinine, age and sex using the CKD-EPI equation; expressed in mL/min/1.73 m²; used for CKD staging but unreliable in acute settings.

Collection of cells that have naturally shed from an epithelial surface into a body fluid or accessible surface, without instrumentation (e.g., Pap smear, sputum, urine, effusion).

An effusion resulting from increased vascular permeability due to inflammation, infection, or malignancy; meets at least one of Light's criteria.

The percentage of filtered sodium excreted in urine: FENa = (urine Na × plasma Cr)/(plasma Na × urine Cr) × 100. < 1%: prerenal; > 2%: intrinsic AKI (tubular damage). Unreliable if diuretics have been given.

Diagnostic procedure using a 22–25 gauge needle to aspirate cells directly from a lesion for cytological examination; can be palpation-guided or image-guided.

The unbound (biologically active) fraction of thyroxine in plasma; measured alongside TSH to assess pituitary-thyroid axis function.

Liver enzyme highly sensitive for cholestasis; also induced by alcohol and enzyme-inducing drugs; used to confirm hepatic origin of ALP elevation.

Benign autosomal recessive condition due to a UGT1A1 promoter polymorphism causing mild unconjugated hyperbilirubinaemia, exacerbated by fasting, stress and illness; all LFTs, haemoglobin and clotting are normal.

A degenerated cellular cast with a coarse granular appearance and brownish pigment; classically associated with acute tubular necrosis.

FNAC pattern of lymph node showing epithelioid macrophage granulomas ± Langhans giant cells; most common cause is tuberculosis; ZN stain sensitivity is ~40-60%, culture or GeneXpert is required.

A transparent, colourless cylindrical cast made of pure Tamm-Horsfall protein, found in small numbers normally and in greater numbers with dehydration, fever, or exercise — essentially benign.

Abnormally dark nuclear staining due to increased DNA content and altered chromatin packaging; a key cytological criterion of malignancy.

Ejaculate volume below 1.4 mL (WHO 2021); may indicate ejaculatory duct obstruction, retrograde ejaculation, or short abstinence interval.

A negative staining technique in which encapsulated fungi (notably Cryptococcus neoformans) appear as clear halos against a dark background in CSF, reflecting the large polysaccharide capsule.

Clear spaces between adjacent mesothelial cells on smears, caused by long surface microvilli; a cytological feature distinguishing reactive mesothelial cells from adenocarcinoma clusters.

Fixed urine specific gravity of 1.010 indicating the tubules have lost both concentrating and diluting capacity, with urine osmolality equalling plasma — a marker of tubular injury or advanced CKD.

Squamous cell showing HPV cytopathic effect: perinuclear cytoplasmic cavitation (halo) with nuclear enlargement and hyperchromasia; hallmark of LSIL.

Three biochemical criteria (pleural/serum protein ratio >0.5, pleural/serum LDH ratio >0.6, pleural LDH >2/3 upper serum normal) used to classify a pleural effusion as an exudate; one criterion is sufficient.

Cervical screening technique where cells are rinsed into a preservative liquid rather than smeared directly; produces a thin monolayer with fewer artefacts and allows HPV co-testing from the same vial.

Romanowsky-type stain applied to air-dried smears; provides excellent cytoplasmic detail including granules, mucin, and metachromatic matrix; preferred for FNAC.

A needle-shaped, negatively birefringent crystal found in synovial fluid of gouty joints; appears yellow when parallel to the slow axis of a polarised light compensator.

Proportion of nuclear area to total cell area; normally ~1:4–5 in squamous cells; elevated (approaching 1:1) in malignant cells.

Shaping of one nucleus by the contour of adjacent nuclei; characteristic of small-cell carcinoma cells in cytological smears.

Oligoasthenoteratospermia — simultaneous reduction in sperm count, motility and normal morphology; the most common pattern in male subfertility.

Sperm concentration below 16 × 10⁶/mL (WHO 2021 lower reference limit); associated with reduced natural conception rates.

A renal tubular epithelial cell or macrophage engorged with lipid droplets, showing Maltese-cross birefringence under polarised light; characteristic of nephrotic syndrome.

Multi-dye cytological stain requiring wet fixation; provides transparent cytoplasm with exquisite nuclear detail; standard for gynaecological, respiratory, and urine cytology.

Variation in cell and nuclear size and shape; marked pleomorphism is a criterion of malignancy; reflects genomic instability in neoplastic cells.

Acute kidney injury caused by reduced renal perfusion (dehydration, haemorrhage, heart failure) with structurally intact tubules; urine Na⁺ < 20 mmol/L and FENa < 1% due to avid tubular reabsorption.

Measure of the extrinsic and common clotting pathway; reflects hepatic synthesis of factors II, VII, IX, X; the most sensitive and earliest indicator of acute hepatic synthetic failure.

The presence of WBCs (>5–10/HPF in a properly collected midstream specimen) in urine, indicating urinary tract inflammation — infectious or sterile.

A urinary cast containing red blood cells trapped in Tamm-Horsfall matrix; pathognomonic of glomerular capillary bleeding and therefore glomerulonephritis.

Immediate assessment of smear adequacy by a cytopathologist during the FNAC procedure using a quick Diff-Quik stain, reducing non-diagnostic rates to < 5%.

Serum albumin minus ascitic fluid albumin; ≥1.1 g/dL indicates portal hypertension as the cause of ascites; <1.1 g/dL suggests non-portal aetiology.

Elevated PTH driven by hypocalcaemia and hyperphosphataemia in CKD; results from reduced renal 1-alpha-hydroxylase activity decreasing active vitamin D synthesis; a feature that distinguishes CKD from AKI on panel.

A large renal stone filling the renal pelvis and calyces, typically composed of struvite (triple phosphate), formed in the setting of chronic infection with urease-producing organisms such as Proteus mirabilis.

Pyuria in the absence of bacterial growth on standard urine culture; causes include renal TB, analgesic nephropathy, interstitial nephritis, and inadequately treated UTI.

A glycoprotein secreted by epithelial cells of the thick ascending limb and early DCT; the structural scaffold of all urinary casts.

The dynamic metaplastic area of the cervix between the original and current squamocolumnar junction; the primary site of HPV infection and cervical carcinogenesis.

An effusion resulting from altered hydrostatic or oncotic pressure without membrane pathology; characterised by low protein, low LDH, and a negative Light's criteria result.

Concordant assessment using clinical examination + imaging (mammogram/ultrasound) + FNAC/cytology to triage breast lesions; all three must agree before a conservative non-surgical approach is justified.

Glycoprotein hormone secreted by the anterior pituitary that drives thyroid hormone synthesis; the single most sensitive blood test for primary thyroid dysfunction.

Lipid-soluble bilirubin before hepatic processing; elevated in prehepatic causes (haemolysis) and impaired conjugation (Gilbert's syndrome); not filtered in urine.

Ratio of serum urea to creatinine (both in mmol/L); > 100 suggests prerenal AKI (tubular urea reabsorption); 40–100 suggests intrinsic renal AKI; < 40 may indicate liver failure or malnutrition.

A highly refractive, broad, homogeneous cast with sharp edges formed in dilated tubules from very slow urine flow; a marker of advanced chronic kidney disease.

A urinary cast containing neutrophils, indicating tubulo-interstitial inflammation — the hallmark of pyelonephritis or acute interstitial nephritis.

Yellow discolouration of CSF supernatant due to bilirubin derived from RBC breakdown, confirming true subarachnoid haemorrhage as distinct from a traumatic lumbar puncture.