Table 3.
Salient features of primary pulmonary myxoid sarcoma and differential diagnoses
| Tumors | Pathological features | IHC | Molecular genetics | Differentiating features from PPMS |
|---|---|---|---|---|
| Primary pulmonary myxoid sarcoma (PPMS) | Well-circumscribed, lobulated, reticular network of delicate lace-like cellular strands and cords in abundant myxoid stroma, tumor cells are stellate, polygonal with also chondrocyte-like or physaliferous-like tumor cells first reported in our case, prominent lymphoplasmacytic infiltrates within and at periphery of tumor. | Vimentin+, EMA+, CK--, TTF-1-, S-100-, calponin-, SMA-, desmin-, ALK-, CD31-, CD34-. | EWSR1-CREB1 fusion | NA |
| Extraskeletal myxoid chondrosarcoma (EMC) | Well-circumscribed, multinodular, tumor lobules separated by fibrous septae, umor cells epithelioid to spindled arranged in cords, strands, or clusters embedded in abundant myxoid stroma. | Vimentin+, S-100+, rarely EMA+, keratins+. |
,EWSR1-NR4A3, TFG-NR4A3, HSPA8-NR4A3, TCF12-NR4A3, FUS-NR4A3 or TAF15-NR4A3 gene fusion |
S-100+, different molecular genetics. Rare as primary in lungs, may present as lung metastasis. |
| Angiomatoid fibrous histiocytoma (AFH) | Sheets and islands of spindle to epithelioid cells with bland ovoid vesicular nuclei and abundant eosinophilic cytoplasm within loose myxoid stroma. | ALK+, desmin+. | EWSR1-ATF1, FUS-ATF1 gene fusion | No lobular or reticular architecture, no chondrocyte-like or physaliferous-like cells, ALK+ and desmin+, with different molecular genetics in AFH. |
| Myoepithelial tumors (MT) | Well-circumscribed, solid sheets, nested or cord-like growth pattern, hyalinized or myxoid stroma, moderate to severe nuclear pleomorphism. | Cytokeratins+, EMA+, S100+, calponin+, SMA+, p63+, GFAP+. |
EWSR1-FUS, EWSR1-PBX1, EWSR1-ZNF444, EWSR1-POU5F1 gene fusions |
No reticular pattern, no chondrocyte-like or physaliferous-like cells, different 1HC and molecular genetics in MT. |
| Pulmonary microcystic fibromyxoma (PMF) | Well-circumscribed, bland spindled to stellate cells widely spaced within prominent fibromyxoid stroma with prominent cystic change. | Vimentin+, CD34-, CD31-, HMB45-, SMA-, desmin-, S-100-, ALK-, CKpan-, EMA-, calretinin-, TTF1- | none | Prominent cystic pattern, much less cellular, no chondrocyte-like or physaliferous-like cells, no diagnostic molecular genetic change and not endobronchially located in PMF. |
| Inflammatory myofibroblastic tumor (IMT) | Areas of myxoid stroma with prominent vessels or hyalinized collagenous stroma, and contain a prominent infltrate of plasma cells and lymphocytes. | SMA+, desmin+, ALK+, rarely keratins+ |
RANBP2-ALK, RRBP1-ALK, ETV6-NTRK3 gene fusions |
No reticular pattern, prominent inflammatory component, no chondrocyte-like or physaliferous-like cells, SMA+, ALK+ with different molecular genetics in IMT. |
| Low grade myxoid liposarcoma (LGML) | Large well-circumscribed, monotonous small ovoid cells with fine chromatin, inconspicuous nucleoli, and scant cytoplasm., many characteristic lipoblasts., prominent plexiform vasculature, myxoid background with areas of mucin pooling, imparting a “pulmonary edema-like” pattern. | S-100+, rarely MDM2+ and CDK4+ | DDIT3-FUS and DDIT3-EWSR1 gene fusions | Characteristic prominent plexiform vasculature, “pulmonary edema-like” pattern, S-100+, different molecular genetics in LGML. Lung is rare site for primary LGML. |
NA not applicable, CK cytokeratin, EMA epithelial membrane antigen, SMA smooth muscle actin