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Q1: Comment on the computed tomogram (see p 605)
This is a contrast enhanced computed tomogram through upper abdomen. There is a well circumscribed, enhancing soft tissue mass in the right upper quadrant lying immediately subjacent to the stomach and the left lobe of liver.
Q2: Describe the macroscopic appearance of the specimen (see p 605)
The specimen shows a fleshy soft tissue mass measuring 11 × 8 × 7.5 cm within the omentum. This has extended to the stomach but has not invaded the stomach wall.
Q3: Describe the histological features (see p 605)
Histology shows that the omental tumour (cellular area) and muscularis propria of the stomach are completely separated by serosal vessels. The tumour is composed of spindle cells arranged in interwoven fascicles.
Learning points
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Isolated primary omental leiomyosarcomas (stromal tumours) should be considered in the differential diagnosis of an upper abdominal mass.
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Awareness of the rare pathologies that involve the omentum and the characteristic radiological appearance of these abnormalities is essential for improving diagnosis and management of these conditions.
Discussion
A leiomyosarcoma is a malignant tumour of smooth muscle. Leiomyosarcomas of soft tissue (as opposed to those arising in the gastrointestinal tract) are most common in the retroperitoneum. The most important criteria for distinguishing a leiomyoma from a leiomyosarcoma is the number of mitotic figures present. The size of the lesion should also be taken into consideration. Golden and Stout stated that “if two or more mitosis per high power field are present, one can feel fairly secure in predicting malignancy”.1They have been recorded in virtually every organ but are relatively uncommon soft tissue sarcomas.2 The greater omentum is rarely involved primarily by disease. In tuberculous peritonitis and carcinomatosis peritonei greater omentum may present as a solidified and thickened mass.3 Stout et al examined 24 solid tumours of the greater omentum, and leiomyomas predominated among benign neoplasms with leiomyosarcomas the most common malignant tumour.4 A few more cases of this rare pathology have been reported in the literature; some of these were diagnosed on computed tomography.5 6 Other rare entities involving the greater omentum that have been reported include rhabdomyosarcoma,7 malignant haemangioendothelioma,8 haemangiopericytoma,9actinomycosis,10 and cystic lymphangioma of the omentum.11 Computed tomography is usually the modality of choice for the evaluation of unusual solid mass lesions, although the site of origin can be difficult to determine before surgery. Knowledge of the spectrum of abnormalities involving the omentum and the characteristic appearance on computed tomography of these is essential for the improved management of these conditions. Leiomyosarcomas are not responsive to either radiotherapy or chemotherapy and the only hope of cure lies in the appropriate surgical resection.
Learning points: tuberculous monoarthritis
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Seen in 1% of tuberculous infections.
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Seen in active or dormant tuberculosis.
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Patients have evidence of exposure to tuberculosis like a positive skin test (typically but not always) or suggestive chest radiography findings.
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Weight bearing joints preferably affected: knee > hip > wrist > other small joints.
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Typical findings on the knee radiograph: joint space narrowing, metaphyseal and subchondral erosions, and subchondral cysts.
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Gold standard of diagnosis: synovial tissue biopsy and tissue cultures
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Treatment is similar to other forms of tuberculosis.
Final diagnosis
Primary leiomyosarcoma of greater omentum.