[4] LGMS and IGMS are now classified together[5] by the World Health Organization (WHO), 2020, in the category of intermediate (rarely metastasizing) fibroblastic and myofibroblastic tumors.
[8] These tumors often recur at the sites of their surgical removal and may metastasize to nearby lymph nodes and distant tissues.
Overall, 51.5% of their tumors were in the head and neck areas (most commonly the tongue, followed by the larynx, gums, mandible, face, skull, and ear canal), 25.2% were in the trunk, and 23.3% were in an arm or leg.
Bone tumors were located in the femurs, mandible, maxilla, tibias, or in one case each the hard palate and sacrum.
[19] Microscopic histopathological analyses of hematoxylin and eosin stained LGMS tissues generally show bundles of atypical spindle-shaped cells in a variably hyalinized (i.e. glassy appearing) stromal background containing collagen fibers.
[4] (The tumor's spindle-shaped cells may infiltrate between individual skeletal muscle fibers[2] to create a characteristic checkerboard pattern.
[14] LGMS should be suspected in cases presenting as nodular masses composed of spindle-shaped cells combining fibroblast and smooth muscle cell features that are arranged in bundles and express α-smooth muscle actin[20] and/or desmin proteins[9] but not vimentin, S-100, CD34 or other marker proteins cited in the previous section.
[1] Following this surgery, individuals should undergo long-term observation to check for post-surgical recurrences and the uncommon instances of metastases.
The study concluded that radiotherapy and chemotherapy had limited effects on survival and therefore should not be routinely used in LGMS, especially for cases in which all tumor cells are removed.
[11] These results and conclusions agree with previous reports finding that LGMS tumors are insensitive to radiotherapy and chemotherapy.
[11] There are case reports where chemotherapy following surgical excision may have been useful in prolonging progression-free survival, for example, in an individual with a pancreatic LGMS tumor (treatment regimen: ifosfamide, pirarubicin, and nedaplatin).