Pathology Associates Of Lexington, P.A.
Pathology Associates Of Lexington, P.A.
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        Soft Tissue Tumors

Soft tissue tumors:

Stanford U. soft tissue surgical path criteria HERE.

  • Pseudotumors:
    • hypertrophic (traumatic) fat necrosis: breast masses, bowel obstructing masses [L-02-6259 A], subcutaneous post-traumatic masses
    • secondary fibroinflammatory lesions: the inciting process may have to be inferred for lack of specific demonstration of etiology but due to reasonable proximate cause; can be intramuscular [L08-11962]; may be para-intestinal [L11-10073].
    • "pseudotumor look-alike" may occurr when lymphoma removed after chemo. [LMC-05-5008].
    • consider various types of panniculitis.
    • sclerosing mesenteritis7: [L-02-6259B].
    • inflammatory myofibroblastic tumor7 (IMFT): has some ALK-1 positive cells.
    • idiopathic retroperitoneal (and there are alternative and mutifocal fibroses) fibrosis7 (Ormond's disease). [LMC-05-4589].
  • Benign:
    1. fat (lipoma):
      • lipoma, NOS
      • fibrolipoma
      • fibroblastic lipoma: benign fat and myxofibrous stroma5 [LMC-02-9501]
      • angiolipoma
      • myxolipoma
      • spindled-celled lipoma [S-02-6261]
      • lymphangiolipoma [S09-2089]
      • chondroid lipoma6.
      • hibernoma [L10-11287 300 grams]
    2. fibrous:
      • fibroma (any location)
      • plantar fibromatosis
      • nodular fasciitis
      • intra-abdominal fibromatosis (IAF): increased mitotic rate, infiltrative, and may be confused with GIST2; IAF is CD34 and S100 neg.
    3. histiocytic:
      • solitary cutaneous histiocytosis X
      • non-X hstiocytoses:
        1. dermatofibroma/histiocytic fibrous histiocytoma: often induces overlying epidermal lesion; (CD34 neg.).[S-01-14537]
        2. solitary reticulohistiocytoma (RH) a few are S100 pos.8.
        3. benign cephalic [on the head] histiocytosis9: infiltrate of histiocytes with eosinophilic cytoplasm and regular nuclei; 3 types: papillary dermal, lichenoid and diffuse. The cells are S100 protein positive and are CD1a negative.
        4. juvenile xanthogranuloma, classical (JXG): CD68 positive8, Touton giant cells & eosinophiles; non-foamy (non-lipidized) type can have elevated Ki67 & mitotic rate; a few are S100 pos. [S-05-7430]
        5. juvenile xanthogranuloma, non-lipidized variant (JXG): pretty much lacks Touton giant cells and foamy hisyiocytes.
        6. MFH/AFX [spindled skin tumors]; must be K903 negative (spindled SCC positive) [L07-11122, L07-10151].
        7. giant cell epulis of the newborn (Neumann's tumor): looks like a benign GCT, below. Is S100 negative. Admixed with the granular cells are variably, maybe almost hypercellular, cellular components that can make the Ki67 look very elevated [L10-5335].
      • giant cell tumor: for example, giant cell tumor of tendon sheath (can have a malignant counterpart...examples)
    4. smooth muscle:
      • leiomyoma: most common in uterus; sometimes removed as intestinal polyps.
    1. Cajal-cell tumors (GIST IHC markers): (see Ackerman text p. 646-647); imaging characteristics (gross pathology) are of fundamental help! Recurrence risk of a resected primary tumor is variable by size, location and proliferative activity. The 2006 stratification table of 2006 by Miettinen & Lasota is in a 201111 report. On-line recurrence-risk calculator HERE which seems to be using the Gold paper with nomogram of 2009 and an adapted image of it from a 2010 presentation HERE. Molecular mutations may indicate best therapeutic agent & Mayo mutations decision charts table of contents HERE and scroll to GIST.
      • uncommitted histology.
      • epithelioid variant: [L07-11009] & sometimes where about half of tumor is other extraneous soft tissue [L12-10080].
      • smooth muscle (small submucosal intestinal leiomyomas are not GIST).
      • neuronal.
    2. skeletal muscle:
    3. nerve:
      • neurofibroma & neurofibromatosis [comprehensive program at MGH]
        1. size...can be huge: 1999 @ U. Chicago, 200 lb. benign NF left 35 year old Lori Hoogewind weighing 90 lbs; 2004 in Romania, 176 lb. NF left Lucica Bunghez weighing 88 pounds.
        2. types: NF1 (peripheral...von Recklinghausen disease), NF2 (central), schwannomatosis, and mosaics (partial manifestation) of each.
      • schwannoma:
        1. myxoid [LMC-01-7004]
      • granular cell tumor (GCT): S100 positive cells granular cells; old terminology, "granular cell myoblastoma". A rare S100-negative mimmic is the epulis, above [L10-5335].
    4. vessels:
      • intralumenal:
        1. pyogenic granuloma4: lobulated & exophytic [LMC-01-7375].
        2. lobular capillary hemangioma: lobular & usually endophytic growth pattern with close packed capillaries without endothelial atypia or multilayering & lesion can have many mitoses; not malignant but needs complete local excision because can recurr, especially if it got into underlying muscle [S07-10107].
      • endothelial & channels (angioma; hemangioma): can even see lesions with variable, anastomosing channels without convincing endothelial pleomorphism or layering [S07-13596; "hobnail hemanioma" or "targetoid hemosiderotic hemangioma", S10-6152]...can "watch and wait" if small & readily accessible (as in skin) & thought clinically to have been removed.
      • composite:
        1. benign angiofibroma & benign cellular angiofibroma [L07-6165]
        2. angiomyxoma
      • perithelial:
        1. benign hemangiopericytoma [LMC-00-2529]
      • perivascular epithelioid cells:
        1. PEComa, NOS [muscle & HMB45 marker positve] [a reference]; they have a two patterns on a spectrum with HMB45-rich type PEComa to epithelioid smooth muscle uterine tumor12.
        2. LAM: pulmonary lymphangiomyomatosis [LMC-05-799]
        3. angiomyolipoma [LMC-02-4220]
        4. clear cell myomelanocytic tumor (CCMMT)
    5. cartilage:
    6. bone:
    7. mixed:
      • angiomyolipoma [LMC-02-4220]
      • angiomyofibroblastoma (AMFB)
      • angiofibroma
        • usual
        • cellular
      • angiomyxoma ("angiomyxoid tumor"):
        • aggressive paratesticular angiomyxoma (recurrs locally).
  • Uncertain behavior:
    1. fat
    2. fibrous
    3. histiocytic:
      • histiocytosis X: bean-shape nucleus with groove; S100 pos.
      • non-X histiocytoses
        • systemic/multifocal reticulohistiocytoma (RH): some S100 pos.8.
        • ambiguous dermatofibroma/histiocytic fibrous histiocytoma vs. DFSP...lesion is CD34 pos. [S-05-7383 CD34 neg.]
      • giant cell tumor, cellular
    4. smooth muscle
    5. Cajal-cell tumors (GIST):
      • uncommitted
      • smooth muscle (small submucosal intestinal leiomyomas are not GIST)
      • neuronal
    6. skeletal muscle: "rhabdomyoid tumor of uncertain malignant potential" [S-02-4041]
    7. nerve
    8. vessels
    9. cartilage
    10. bone
    11. mixed:
  • Malignant (sarcoma):
    1. MSKCC treatment options nomograms: click sarcoma on drop-down menu
    2. fat:
      • myxoid liposarcoma: gelatinous, myxoid cut surface and histology that reminds of chondroid1 [S-01-10450]
      • dedifferentiated liposarcoma [LMC-03-5283 groin]
    3. fibrous:
      • fibrosarcoma:
      • fibromyxoid sarcoma: swirling, whorled growth pattern of spindled cells with sometimes scant myxoid "look" [S-02-13318]
    4. histiocytic:
      • histiocytosis X
      • non-X histiocytoses
        1. malignant fibroblastic fibrous histiocytoma (dermatofibrosarcoma protuberans...DFSP...CD34+): at discovery in a patient, about half are non-protuberant, and of those non-protuberant, 29% are morphea like, 19% are atrophoderma like, and 42% are angioma like.
        2. malignant histiocytic fibrous histiocytoma (MFH)[S-01-14379; L09-5671]. Alpha-1 antichymotrypsin positive.
          1. superficial: subQ tissue
          2. deep: often in muscle, fascia, etc.
        3. myxoid MFH [LMC-01-6923]
        4. malignant giant cell tumor (H&E stain straightforeward sarcoma).
        5. giant cell tumor of soft parts (giant cell variant of MFH), including tendon sheath: locally recurring low grade sarcoma [L08-9354; L13-9564].
        6. fibroxanthosarcoma2.
        7. inflammatory fibrous histiocytoma2.
        8. malignant pleomorphic fibrous histiocytoma (xanthosarcoma) [LMC-01-6252, LMC-02-6806].
    5. smooth muscle:
    6. Cajal-cell tumors (GIST):
      • uncommitted
      • smooth muscle (small submucosal intestinal leiomyomas are not GIST)
      • neuronal
    7. skeletal muscle:
    8. neural:
      • myxoid malignant schwannoma:
      • PNET: bone or soft tissue Ewings [FNA-05-68 massive retroperitoneal]
      • malignant granular cell tumor: old terminology, "alveolar soft part sarcoma"
    9. vessels:
      • endothelial cells:
      • perithelial cells:
    10. cartilage:
    11. bone:
    12. mixed: 
      • mixed mesenchymal sarcoma [LMC-02-4255]
    13. mimics:
      • myxoid malignant melanoma:


  1. AFIP Soft Tissue Fascicle 30, 3rd Series, 2001.
  2. AFIP Soft Tissue Fascicle 1, 2nd Series, 1982, Dr. R. Lattes 
  3. AJSP 24:947-957, 2000
  4. Enzinger & Weiss
  5. Hajdu, S. I. Pathology of Soft Tissue Tumors, 1979 [text, EBS's office]
  6. Arch. Path. & LM, 125(9):1224-26, 9/01.
  7. Rosai J, Rosai AND Ackerman's Surgical Pathology, 9th Ed., p. 2389-2394, 2004.
  8. Tomaszewski MM, Lupton GP, (from the AFIP), J Cutan Pathol. 1998 Mar;25(3):129-35. [7 of 29 JXGs & RHs were S100 pos.]
  9. Dermatology Atlas:
  10. Koch BL, et al, "Cogenital Epulis", American Journal of Neuroradiology, 18(4):739-741, 1997.
  11. Patil DT & Rubin BP, Gastrointestinal...", Arch. Path. and Lab. Med.135(10):1298-1310, October 2011.
  12. Vang R, Kempson RL, Am. J. Surg. Pathol., HERE.


(posted beginning file Nov. 2001; latest addition 1 December 2015)

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