Make sure you know where the primary tumor is. The tumor in the lung, bone, limb, skin, could be a metastasis from a primary in another site.

The recognized primaries are uterine, retroperitoneal, gastrointestinal, great vessels. Tumors of these sites are very unlikely to be metastases from another site...although uterine primaries can seed throughout the abdominal cavity as well.

Uterine leiomyosarcoma is often hidden within 'benign' uterine fibroids. Sometimes the pathologist reporting on the hysterectomy specimens misses the LMS cells hidden away within. The lung tumor that may appear years later is then a metastasis, and not a lung primary.

Knowing that the lung tumor is a metastasis is not only important for the staging of the LMS, but for redirecting attention to possible local recurrence that was missed in the pelvic or abdominal cavities.

Lungs are classic sites of metastatic tumor. They are also capable of sending out metastases as well, to limbs, skin, bone...in fact to every organ or system that has a direct blood supply.

Livers are also classic sites of metastatic tumor. Abdominal tumor tends to metastasize to liver, but so can lung. However, there has also been reported a case of LMS with a primary tumor in the liver. 

LMS in the heart, or adrenal gland, or thyroid gland, or bone, or muscle could be primary or metastatic. There are very few sites which have never been reported as a primary LMS, and very few sites which have never been reported as metastatic. 

Leiomyosarcoma does not primarily metastasize by lymphatic spread, but it can and does spread to lymph nodes. Regional lymph node involvement is more common in pelvic and abdominal LMS, where it can occur in up to 14% of the cases, but can also occur in other sites, as well. But there was also a case reported of an LMS primary in a lymph node. 

So a thoughtful and responsible approach to the diagnosis of LMS in ANY site, is a thorough examination and a Spiral CT Scan of Chest, Abdomen, Pelvis with and without contrast, looking for more tumors in other places.