Masses in the muscles

Submitted by Danny Markowski and Neil Keshvani
Published October 5, 2019

A 61 year-old-man with hypertension, hyperlipidemia, and obesity presented with several weeks of progressively worsening lower abdominal pain that awoke him from his sleep.   He noticed tightness in his right lower abdomen that did not improve with changes in position. He also reported worsening left-sided lower back pain over the past several weeks.  The patient denied fevers, chills, night sweats, bone pain, cough, diarrhea, or a change in bowel movements. He has a 60-pack smoking history and previously worked as a truck driver in the construction and plumbing industries. 

 Physical examination revealed a palpable abdominal mass in the right lower quadrant, with mild tenderness to palpation.  Physical examination revealed tenderness to palpation along the left paraspinal musculature from L1-L4 and no vertebral point tenderness.  

 Initial laboratory evaluation revealed a white blood cell count of 22 per mm3, (reference range 4 - 11 per mm3) which was unchanged from previous testing in 2015.  Workup at that time had included a negative BCR-abl FISH and Jak2 mutation as well as a normal erythropoietin level.  Chest radiograph revealed a large round mass in the right mid/lower lung field. CT scan revealed several masses throughout the body, including a pleural mass measuring 10 x 6.5 centimeters and peritoneal deposits from a multifocal soft tissue malignancy involving the right iliac, right serratus anterior, right lower abdominal rectus/oblique, and bilateral gluteus muscles (See Images 1&2).  Of note, a CT scan was performed one year prior without evidence of any of these masses. A biopsy of the mass was performed by interventional radiology, which revealed sarcomatoid mesothelioma.

Questions:

1) What is the most common cause of mortality in a patient with mesothelioma? 

1. Respiratory failure

2. Small bowel obstruction

3. Cardiovascular event

4. Infection

2) What are the most common muscular sites of metastases?

1. Gluteal

2. Thoracic wall

3. Paraspinal

4. Iliopsoas

5. Abdominal wall

Answers and Discussion:

Question 1 - Answer (A)

Decreased respiratory function is the leading cause of death in patients with mesothelioma.  This is believed to be due to tumor size decreasing lung capacity and tumor/ pleural fluid changes reducing lung expansion.  Risk for cardiovascular disease has also been shown to be increased in those with occupational exposure to asbestos.1

Question 2 - Answer (D)

Surov et. al 2009 investigated skeletal muscle metastases to determine most common locations affected by metastatic mesothelioma.  Nearly 28% of skeletal muscle metastases were located in the iliopsoas muscle. Paraspinal muscles were the second most common location at 25%, followed by lower extremity musculature.

Teaching / take home points

• Mesothelioma is primarily caused by the inhalation of asbestos fibers. Workers in the construction and plumbing industries are at the highest risk. 

• Prognosis for malignant pleural mesothelioma is poor, with an overall average survival of 9-17 months following diagnosis.  Very rarely are patients cured of the disease.

References

1. Harding A, Darnton A, Osman J, “Cardiovascular disease mortality among British asbestos workers (1971–2005).” Occup Environ Med Published Online First: 02 April 2012. doi: 10.1136/oemed-2011-100313

2. Surov, Alexey, et al. “Skeletal Muscle Metastases: Primary Tumours, Prevalence, and Radiological Features.” European Radiology, vol. 20, no. 3, 2009, pp. 649–658., doi:10.1007/s00330-009-1577-1.

Authors

Danny Markowski, MD, is an intern in Internal Medicine at the University of Texas Southwestern Medical Center, Dallas, TX.

Neil Keshvani, MD, MS, is a junior resident in Internal Medicine at the University of Texas Southwestern Medical Center, Dallas, TX.