Why is myositis associated with bulky ovaries, structures, and ascites, suggesting an underlying malignancy like ovarian cancer?

Myositis with Bulky Ovaries, Ascites, and Pelvic Structures: Paraneoplastic Ovarian Cancer

Myositis presenting with bulky ovaries, ascites, and enlarged pelvic structures strongly suggests underlying ovarian malignancy as a paraneoplastic syndrome, particularly dermatomyositis (DM) or polymyositis (PM), which occur in 25% of adult DM patients within 0-5 years of disease onset, with ovarian cancer being disproportionately common in women over 40. 1

Why These Findings Occur Together

The Paraneoplastic Connection

• Dermatomyositis and polymyositis are well-established paraneoplastic syndromes associated with ovarian cancer, with ovarian malignancy occurring in 13.3% of all female DM patients and 21.4% of women over 40 with DM—dramatically higher than the 1% baseline population risk. 2

• Breast and ovarian cancers are the most common malignancies in women with DM, making ovarian cancer screening essential when myositis is diagnosed. 1

• The myositis typically precedes the cancer diagnosis in approximately 64% of cases (9 of 14 patients in one series), occurs concomitantly in 29%, and follows diagnosis in only 7%. 3

Why Ovarian Cancer Presents with These Specific Findings

The bulky ovaries, ascites, and enlarged structures reflect advanced-stage ovarian cancer, which is unfortunately the typical presentation when discovered in the context of paraneoplastic myositis:

• Advanced ovarian cancer (stages III-IV) characteristically produces ascites and abdominal masses leading to increased abdominal girth, bloating, nausea, and early satiety. 1

• Ascites is a defining feature of advanced ovarian cancer staging: Stage IC and IIC specifically include "ascites present containing malignant cells" as diagnostic criteria, while stage III involves peritoneal implants and ascites. 1

• The presence of large lesions, multi-locular cysts, solid papillary projections, irregular internal septations, and ascites are highly suggestive of ovarian cancer on imaging. 1

The Tragic Clinical Reality

Physical examination and imaging techniques consistently fail to detect early ovarian cancer in patients with dermatomyositis/polymyositis—when detected (usually by abdominopelvic examination or CT), the cancer is already advanced with poor survival. 3

• In the largest retrospective series, all 14 patients with myositis and ovarian cancer had advanced disease at diagnosis, with mean age 59 years. 3

• CA-125 is elevated in approximately 85% of patients with advanced ovarian disease but only 50% with early-stage disease, explaining why these cancers present late. 1

Critical Diagnostic Algorithm for Myositis Patients

Immediate Red Flags Requiring Ovarian Cancer Workup

When myositis presents with any of the following, assume ovarian malignancy until proven otherwise:

• Abdominal distension, ascites, or increased abdominal girth 1, 4
• Pelvic mass on examination 1
• Age over 40 years (21.4% risk of ovarian cancer in DM patients) 2
• Unexpected findings: hepatosplenomegaly or extensive lymphadenopathy suggest malignancy 1

Mandatory Screening Protocol

For any woman over 40 with newly diagnosed dermatomyositis or polymyositis, perform:

1. Transvaginal and transabdominal ultrasound by expert examiner (first-line imaging) 1

2. Serum CA-125 measurement (elevated in 85% of advanced disease) 1

3. CT thorax, abdomen, and pelvis with contrast to assess for metastases, ascites, and peritoneal disease 1

4. Pelvic examination looking for adnexal masses 1

5. Consider elevated CA-125 at DM diagnosis as predictive of increased risk for ovarian or primary peritoneal malignancy 1

Common Clinical Pitfalls

Critical Mistakes to Avoid

• Never attribute ascites and abdominal distension to myositis itself—these findings indicate advanced malignancy requiring immediate investigation. 4, 5

• Do not dismiss normal CA-125 levels as excluding ovarian cancer—up to 50% of early-stage cases have normal CA-125. 1, 5

• Avoid delaying cancer workup while treating myositis symptoms—the cancer is typically already advanced when myositis presents, and survival depends on prompt diagnosis. 3

• Do not perform age-inappropriate screening—in women under 40 with myositis, ovarian cancer is rare unless specific examination findings suggest it (hepatosplenomegaly, lymphadenopathy). 1

Why Imaging Fails Early Detection

The fundamental problem is that paraneoplastic myositis typically manifests when ovarian cancer is already advanced (stage III-IV), at which point bulky ovaries, ascites, and peritoneal disease are already present. 3 This explains why:

• Physical examination detects masses only when disease is advanced 3
• CT imaging shows obvious abnormalities because cancer has already spread 3
• Ascites is present because peritoneal seeding has occurred 1

The Immunosuppression Complication

Treating myositis with immunosuppression (steroids, IVIG) can complicate postoperative recovery in ovarian cancer patients, creating a therapeutic dilemma. 6, 7 However, clinical improvement in myositis symptoms often occurs after initiating cancer treatment, suggesting the paraneoplastic process may resolve with tumor control. 7