Testicular microlithiasis

Testicular microlithiasis is a relatively uncommon condition that represents the deposition of multiple tiny calcifications throughout both testes. 

Diagnosis

The most common criterion for diagnosis on ultrasound is that of at least five microcalcifications in one testis although the European Society of Urogenital Radiology (ESUR) recommends a criterion of at least five microcalcifications in a single field of view ¹².

Epidemiology

Testicular microlithiasis is seen in up to 0.6% of patients undergoing scrotal ultrasound. Some reports suggest that it may be present in up to 5.6% of the general population between 17 and 35 years of age ³. Although testicular microlithiasis is present in ~50% of men with a germ cell tumor, it is very common in patients without cancer, and a direct relationship between the two has been debated. 

Associations

• testicular germ cell tumor

• Klinefelter syndrome

• cryptorchidism

• testicular infarct

• testicular granulomatous disease

• infertility ¹⁴

• Down syndrome

• alveolar microlithiasis

Clinical presentation

Testicular microlithiasis per se is asymptomatic and is usually found incidentally when the scrotal content is examined with ultrasound, or found in association with symptomatic conditions. 

Pathology

In the majority of cases, testicular microlithiasis is bilateral ^ref. The microcalcifications are likely a marker of tubular degeneration, but not a risk factor for tubular degeneration ¹⁰.

Classification

The ESUR has classified testicular microlithiasis into three groups based on ultrasound findings ^12,17:

• limited testicular microlithiasis: <5 microcalcifications per field of view

• classic testicular microlithiasis: ≥5 microcalcifications per field of view

• diffuse testicular microlithiasis: numerous microcalcifications in a "snowstorm" appearance

It is unclear if a grading system adds prognostic value, however, relative to follow up based on known risk factors.

Radiographic features

Ultrasound

Ultrasound is the modality of choice for examining the testes. Microlithiasis appears as small non-shadowing hyperechoic foci ranging in diameter from 2-3 mm ¹⁷. These foci, often uniformly sized, occur within the testicular parenchyma and although usually distributed uniformly, may be clustered or distributed peripherally or segmentally ^2,12.

Treatment and prognosis

Testicular microlithiasis is in itself asymptomatic and benign. A relationship with testicular tumors, in particular germ cell tumors (GCTs) is controversial. An ~12 fold increased risk of GCT in symptomatic testes with microlithiasis has been reported (with microlithiasis found in approximately 50% of GCT cases), however, no increased risk has been found in asymptomatic testes. It is also unclear whether early detection confers any benefit over self-exam. As such, screening is unlikely to be beneficial ^1,14.

Some publications advise routine self-examination, rather than sonographic surveillance ⁵ while others recommend annual ultrasound follow up when it is accompanied by other premalignant factors ⁶. The European Association of Urology (EAU) suggests considering testicular biopsy if the patient is higher risk (e.g. testicular dysgenesis, contralateral GCT, etc.) to evaluate for germ cell neoplasia in situ ¹⁶.

The ESUR advises annual ultrasound follow-up until age 55, only if a risk factor for malignancy is present ¹²:

• maldescent

• orchidopexy

• testicular atrophy (e.g. volume under 12 cc)

• previous germ cell tumor ¹⁴

• family history of germ cell tumor

Men with isolated testicular microlithiasis should be encouraged to perform a monthly testicular self-examination ¹⁷.