Testicular Fnac in infertility md pathology 10 marks question

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testicular FNAC infertility cytology patterns azoospermia MD pathology exam

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https://pmc.ncbi.nlm.nih.gov/articles/PMC10787927

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Testicular FNAC in Male Infertility

Introduction

Fine needle aspiration cytology (FNAC) of the testis is a minimally invasive, quick, and reliable technique used in the evaluation of infertile males, particularly those presenting with azoospermia (absence of sperm in ejaculate). It was first described by Obrant and Persson (1965) and later popularized as a diagnostic tool by Scandinavian workers. It serves as an important alternative to open testicular biopsy, providing equivalent cytological information with less morbidity.

Indications

Azoospermia - to differentiate obstructive (post-testicular) from non-obstructive (testicular/pre-testicular) causes
Severe oligospermia (sperm count < 5 million/mL)
Pre-treatment evaluation before assisted reproduction (IVF/ICSI)
To detect retrievable sperm for sperm retrieval procedures
Follow-up after treatment (e.g., varicocelectomy, hormonal therapy)

Technique

Patient preparation: Outpatient procedure; local anesthesia (2% lignocaine) applied to scrotal skin and spermatic cord.
Needle: 23-25 gauge, 1.5-inch needle attached to a 10 mL syringe.
Sites: Aspirated from three locations (upper, middle, and lower poles) of each testis to account for focal variation in spermatogenesis.
Smear preparation: Air-dried smears stained with Giemsa/May-Grunwald-Giemsa (MGG) or wet-fixed smears stained with Papanicolaou (PAP) stain.
Cell count: A minimum of 200 cells are counted. The Testicular Fine Needle Aspiration Score (TFNAS) or Sperm Count Index (SCI) can be calculated.

Normal Cytological Pattern

A normal smear shows all stages of spermatogenesis in an orderly sequence:

Cell Type	Morphology
Spermatogonia	Round cells with dark nucleus, peripheral chromatin; resting against basement membrane
Primary spermatocytes	Largest germ cells; coarse chromatin; paired chromosomes visible
Secondary spermatocytes	Smaller, briefly seen
Spermatids (round)	Small round cells with dense round nucleus
Spermatids (elongated)	Elongated nucleus, developing tail
Spermatozoa (mature)	Oval head with flagellum
Sertoli cells	Large, pale, elongated nucleus with prominent nucleolus; cytoplasmic extensions; found singly or in clusters
Leydig cells	Polygonal, granular eosinophilic cytoplasm; found in stromal clusters

The germ cell to Sertoli cell ratio is normally approximately 13:1.

Cytological Patterns in Infertility

1. Normal Spermatogenesis

All germ cell types including mature spermatozoa are present
Usually indicates obstructive azoospermia (post-testicular block)
Prognosis: Excellent - surgical correction (vasovasostomy, epididymovasostomy) is often successful
Seen in ~27% of azoospermic biopsies (also associated with Young syndrome, congenital bilateral absence of the vas deferens)

2. Hypospermatogenesis

Reduced numbers of all germ cell types present, but the sequence of maturation is intact
Spermatozoa may be present but markedly reduced
Sertoli cells appear normal
Cause: hormonal, varicocele, partial obstruction, general systemic illness
Prognosis: May respond to medical therapy (e.g., gonadotropins)

3. Maturation Arrest (MA)

a. Early Maturation Arrest (at primary spermatocyte level)

Spermatogonia and primary spermatocytes present
No spermatids or spermatozoa
Sertoli cells normal

b. Late Maturation Arrest (at spermatid level)

All germ cell types present up to round spermatids
No elongated spermatids or spermatozoa
Late MA has a better prognosis for sperm retrieval than early MA
Cause: Genetic defects (Y chromosome microdeletions, AZFb), toxic agents, heat stress
Prognosis: Poor for natural conception; sperm retrieval (TESE) may yield immature spermatids for ICSI

4. Sertoli Cell Only Syndrome (SCOS) / Germ Cell Aplasia

Smears show Sertoli cells only - no germ cells at any stage
Sertoli cells appear as clusters with large, pale, oval to elongated nuclei and prominent nucleolus
Tubular basement membrane thickening on histology
Normal Leydig cells
Cause: Genetic (AZFa deletion, Klinefelter syndrome 47,XXY), orchitis, cryptorchidism, cytotoxic therapy
Prognosis: Very poor; TESE usually fails unless focal spermatogenesis is present on mapping biopsy

5. Testicular Atrophy / Tubular Sclerosis (Generalized Fibrosis)

Smears are paucicellular with stromal fragments
Fibroblasts, tubular ghost outlines, hyalinized material
Cause: End-stage testicular failure - post-orchitis (mumps), post-torsion, radiation
Prognosis: Very poor; no treatment available

Quantitative Methods

Sperm Count Index (SCI) / Johnsen Score equivalent in FNAC

The Sperm Count Index (Mehrotra, 1992) is calculated as:

SCI = (N spermatozoa ÷ N Sertoli cells) × 100

SCI > 20: Normal spermatogenesis
SCI 10-20: Hypospermatogenesis
SCI 1-9: Maturation arrest
SCI 0: SCOS or atrophy

Comparison: FNAC vs. Open Testicular Biopsy

Parameter	FNAC	Open Biopsy
Invasiveness	Minimal (needle prick)	Surgical incision needed
Anesthesia	Local	Local/general
Complications	Minimal (hematoma rare)	Hematoma, infection, scarring
Can assess basement membrane	No	Yes
Can diagnose CIS/ITGCN	No	Yes
Sampling error	Yes (focal lesions missed)	Less (larger tissue)
Correlation with histology	~85-90%	Gold standard
Repeat sampling	Easy	Difficult
Cost	Less	More

Key limitation: FNAC cannot assess tubular architecture, basement membrane integrity, or diagnose carcinoma in situ (ITGCN/CIS) - for these, open biopsy is required.

Clinical Significance / Role in Management

Obstructive vs. Non-obstructive azoospermia: The single most important clinical use - FNAC showing normal spermatogenesis points to obstruction, while SCOS/MA indicates primary testicular failure.
Sperm retrieval (TESE/TESA/micro-TESE): A positive FNAC (spermatozoa present) predicts successful surgical sperm retrieval for ICSI.
Avoids unnecessary surgery: In SCOS, identifies futile surgical sperm retrieval.
Genetic counseling: SCOS pattern often prompts AZF deletion testing and Klinefelter workup.
Bilateral sampling: Important because spermatogenesis can differ between right and left testes.

Summary Table of Cytological Patterns

Pattern	Germ Cells	Spermatozoa	Sertoli Cells	Likely Cause
Normal spermatogenesis	All stages	Present	Normal	Obstructive azoospermia
Hypospermatogenesis	All stages reduced	Rare/absent	Normal	Hormonal, varicocele
Early MA	Up to primary spermatocytes only	Absent	Normal	Genetic, toxic
Late MA	Up to spermatids only	Absent	Normal	Genetic
SCOS	Absent	Absent	Only cells present	AZFa deletion, Klinefelter
Tubular sclerosis/Atrophy	Absent	Absent	Absent/degenerate	Post-orchitis, radiation

Conclusion

Testicular FNAC is a simple, safe, and cost-effective investigation that closely correlates with open testicular biopsy histology (correlation ~85-95%). It accurately classifies the pattern of spermatogenesis, differentiates obstructive from non-obstructive azoospermia, and guides clinical management including the decision for surgical sperm retrieval. Its main limitation is the inability to assess tubular architecture and diagnose CIS. In modern infertility practice, testicular FNAC has largely replaced diagnostic open biopsy as the first-line tool for histological assessment.

Key references: Pathology Outlines - Testis Infertility; Campbell-Walsh Urology; Rane et al., Ann Clin Cytol Pathol 2018; PMC10787927.

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