Physiological cysts

Physiological cysts tend to regress spontaneously without any intervention in most cases.

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  Follicular Cysts : Follicular cysts typically occur due to the failure of ovulation or the failure of a mature follicle to rupture, resulting in the formation of a follicular cyst. Generally simple and measuring less than 6 cm, the majority of these cysts resolve by 16 weeks of gestation.

  
  
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  Corpus Luteal Cyst : The corpus luteum is responsible for secreting progesterone in the early 1st trimester of pregnancy until the placenta assumes this role. Corpus luteal cysts generally regress by 8 weeks of gestation. Failure to recognize a corpus luteal cyst can lead to unnecessary intervention and an increased risk of miscarriage in the early first trimester if it is mistakenly removed.

  
  
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  Haemorrhagic Cyst : Acute bleeding into a cyst can lead to the formation of a haemorrhagic cyst, often accompanied by abdominal pain. In the majority of cases, symptoms are brief and temporary, and if the patient is stable, conservative management is advisable.

Pathological cysts

Pathological cysts generally do not resolve over time. They can be benign, borderline or malignant.

Mature cystic teratoma (dermoid cyst): These are the most common benign ovarian cysts found in pregnancy. They are generally asymptomatic when <6 cm but are prone to torsion if larger. Various distinctive sonographic features have been identified to facilitate their diagnosis, including:

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  A focal or diffuse hyperechoic component.

  
  
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  Areas displaying acoustic shadowing, known as the “tip of the iceberg” sign.

  
  
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  Echogenic lines and dots, also termed the dermoid “mesh” or “dot-dash” sign.

The hyperechoic component, referred to as a Rokitansky nodule, usually corresponds to a mixture of hair and sebaceous material or, on occasion, calcification, potentially associated with bone or tooth elements. While the presence of floating echogenic globules within a large mass is an uncommon characteristic, it is reportedly a strong indicator of a dermoid cyst.

Malignant transformation is a serious potential complication of mature cystic teratomas, occurring in up to 2%, with 80% of cases being squamous cell carcinomas. Additional potential complications include hyperthyroidism resulting from teratomas with thyroid hormone-secreting tissue and chemical peritonitis following spontaneous or iatrogenic dermoid rupture.

Endometrioma: Endometriomas are seen as cystic lesions with diffuse low-level internal echoes, often described as “ground glass,” which is present in 95% of endometriomas. When observed through MRI scanning, endometriotic cysts typically display homogeneous high-signal intensity on T1-weighted images and low-signal intensity on T2-weighted images. Asymptomatic endometriomas can be monitored using ultrasound after pregnancy. In cases where concerns exist about the cyst’s potential malignant transformation, MRI can be a valuable tool for assessment.

Borderline ovarian tumours (BOTs)

Borderline ovarian tumours (BOTs), also known as atypical proliferative tumours, are a distinct subset of epithelial ovarian tumours that exhibit abnormal cell proliferation but lack the invasive characteristics typically seen in malignant ovarian cancers. They have a better prognosis compared to fully malignant ovarian cancers, with a generally low risk of spreading or recurrence.

Borderline ovarian tumours are primarily classified based on their histological subtype, similar to invasive epithelial ovarian cancers. The classification includes:

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  Serous borderline tumours (SBT):

  
  
  
  
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    The most common type of BOT.

    
    
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    Characterized by papillary structures and serous fluid-filled spaces.

    
    
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    Can have non-invasive or micro-invasive implants in the peritoneum.

    
    
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    Rarely, serous BOTs can progress to low-grade serous carcinoma.

  
  
  
  
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  Mucinous borderline tumours (MBT):

  
  
  
  
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    Second most common type.

    
    
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    Composed of mucin-producing epithelial cells.

    
    
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    Can be intestinal-type (more common) or endocervical-type.

    
    
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    Less likely to spread beyond the ovary, but occasionally associated with pseudomyxoma peritonei if rupture occurs.

  
  
  
  
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  Endometrioid borderline tumOURS:

  
  
  
  
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    Less common.

    
    
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    Resemble the endometrial tissue of the uterus.

    
    
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    Often associated with endometriosis.

  
  
  
  
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  Clear cell borderline tumours:

  
  
  
  
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    Rare and resemble the clear cell type of invasive ovarian cancers.

    
    
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    Their biological behaviour and clinical relevance are less well understood.

  
  
  
  
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  Brenner borderline tumours:

  
  
  
  
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    Extremely rare.

    
    
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    Composed of transitional cells resembling the bladder epithelium.

  
  

Malignant ovarian tumours

Malignant ovarian tumours are cancerous growths that arise from different cells within the ovaries. These tumours are categorized based on the type of cell they originate from. Types of malignant ovarian tumour are as follows.

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  Epithelial tumours:

  
  
  
  
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    Most Common: Over 90% of ovarian cancers are epithelial in origin.

    
    
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    Types:

    
    
    
    
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      Serous : The most common and aggressive form.

      
      
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      Mucinous : Can grow large and is less aggressive but harder to treat once metastasized.

      
      
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      Endometrioid and Clear Cell : Often associated with endometriosis.

    
    

  
  
  
  
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  Germ cell tumours:

  
  
  
  
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    Rarer (5–10%): Typically found in younger women, these tumours arise from the cells that produce eggs.

    
    
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    Types:

    
    
    
    
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      Dysgerminoma : The most common germ cell malignancy.

      
      
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      Yolk sac tumour, Teratoma : Other forms, each with varying prognosis and treatment approaches.

    
    

  
  
  
  
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  Stromal tumours:

  
  
  
  
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    Rare (1–2%): These originate from the ovarian tissue that produces hormones. Examples include granulosa cell tumours and Sertoli-Leydig tumours.

    
    
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    Hormonal Impact: These can sometimes cause symptoms related to oestrogen or testosterone overproduction.

  
  

Theca lutein cysts

These cysts are commonly linked to gestational trophoblastic disease. Additionally, they might be present in pregnancies complicated by fetal hydrops. Resembling ovarian neoplasms, these cysts frequently exhibit a multiseptated or multiple adjacent cyst appearance. The diagnosis is often suggested by the bilateral nature of these cysts and their recognized clinical associations. In cases where ovulation induction or gestational trophoblastic disease is absent, the term “hypereactio lutinalis” may be used to characterize these cysts.

Decidualized endometrioma

Although rare, it is crucial to diagnose these lesions as they can unnecessarily raise concerns about ovarian malignancy. Typically cystic, these lesions often feature small solid components with detectable internal blood flow through Doppler studies. Unfortunately, colour Doppler imaging is unable to distinguish between a decidualized endometrioma and ovarian malignancy. Therefore, awareness of this entity, comparison with scans of a known pre-pregnancy endometrioma, monitoring changes in size or appearance during pregnancy, and employing additional imaging modalities such as MRI are all crucial for accurate diagnosis and management.

Luteoma of pregnancy

This uncommon benign ovarian cyst during pregnancy lacks distinctive sonographic characteristics. Diagnosis may be supported by the presence of maternal virilization, and hirsutism along with elevated serum androgens can aid in the diagnostic process.