Clinical History
A 55 year old male patient with fever, constipation, weight loss (5 kg in one month) and abdominal pain came to our Emergency Department.
Imaging Findings
Abdominal US showed a round mass (9x8 cm in diameter) in the hypogastrium-right iliac fossa, with inhomogeneous echogenicity and few gas bubbles inside (Fig 1). A MDCT examination better demonstrated a mass anteriorly to the aortic bifurcation which involved the mesenteric root. This lesion exhibited a mixed pattern: fluid on the right and solid tissue on the left with enhancement after CM injection, and appeared undissociable from an adjacent ileal loop of bowel (Fig 2a-c). The lesion wall was thickened and irregular; shading of adjacent mesenterial fat tissue and crowding of perilesional vessels were also detected. Surgery was performed 2 days later. Pathology findings depicted a spindle-like cells proliferation with disarrayed architecture (Fig 3a,b). Immunohistochemical assay revealed positivity for desmin and alpha-actins, while negativity was shown for CD34, CD117 (c-kit), S100 protein and MDM2 expression. Final diagnosis was favourable for a low-grade leiomyosarcoma. The patient was discharged 7 days after surgery in good physical conditions.
Discussion
After liposarcoma, leiomyosarcoma represents the second most common retroperitoneal tumour of the adult (11-30%) with a major incidence in females during their V-VI decade. The lesion appears macroscopically as a well-defined neoplasm characterized by expansive rather than infiltrative growth. Because of slow growth clinical signs and symptoms appear late when the tumour has reached a conspicuous size. Clinical and laboratory values are not specific, so the diagnosis often is belated. Microscopically, leiomyosarcorma has a typical pattern of spindle-shaped cells with elongated, occasionally truncated, blunt-ended nuclei. Mitoses may not correlate with the biologic behaviour.
Three subtypes are known: extravascular (62%), intravascular (5%) and mixed intra-extravascular (33%). The case shown here is an extravascular subtype and appeared as a large mass, surrounded by a pseudocapsule with large necrotic areas. The necrotic areas in extravascular leiomyosarcomas are often more extensive than in other retroperitoneal neoplasms. MDCT demonstrates a solid lesion with density-value similar to muscle tissue and hypodense areas due to necrosis; after iv CM administration an inhomogeneous enhancement is achieved. Rarely these neoplasms appear as an entirely solid or entirely cystic mass. Natural history and prognosis are characterized by high mortality within 5 years and local recurrence in 40-70% of cases.
Differential Diagnosis List
Abdomino-pelvic low-grade spindle-like cells extravascular leiomyosarcoma, arising from smooth-muscle tissue.
GIST
Intraperitoneal abscess
Bowel neoplasm with secondary abscess
Bowel leiomyoma
Final Diagnosis
Abdomino-pelvic low-grade spindle-like cells extravascular leiomyosarcoma, arising from smooth-muscle tissue.