Pathology Notes

Neurofibroma Updated: 03/28/2020 © Jun Wang, MD, PhD General features Benign tumor with nerve sheath differentiation If multiple, likely associated with neurofibromatosis type 1 Malignant transformation rare Subtypes Plexiform: Irregularly expanded nerve bundles with nodular appearance, prominent myxoid matrix; associated with NF1 Diffuse cutaneous: Large plaque like elevation , typically NF1-associated Superficial cutaneous: Pedunculated nodules, solitary (sporadic) or multiple (likely NF1 associated) Clinical presentations Flesh-colored, soft nudule, solitary or multiple Slow growing, painless May have abnormal sensation (electric-like shock with light touch) Key morphological features Non-encapsulated spindle cell proliferation Thin slandering nuclei (coma like) Fibrillary background May be plexiform Markers Positive for S-100 May be focally positive for CD34 and Factor XIIIa Genetic abnormalities NF1 if neurofibromatosis Treatment

Myxoid liposarcoma   Updated: 08/18/2021 © Jun Wang, MD, PhD General features Used to be called myxoid/round cell liposarcoma More common 40-50s Adults in 20’s to 40’s Clinical presentations Most common location: Usually extremities, esp. proximal thigh Pathogenesis Deregulation of NF-kB pathway by FUS-DDIT3 chimeric protein Key morphological features Low grade: Myxoid background with mature adipocytes High grade: Sheets of round cells Delicate vasculature Lipoblast, less differentiated cells with round to oval dark nuclei Markers S-100 Genetic abnormalities FUD-DDIT3 Treatment Wide excision Raiotherapy/chemotherapy Poor prognostic factors Poorly differentiated (round cell) component Large size, necrosis, high Ki-67 index, p53 overexpression Back to soft tissue tumors Back to contents

Malignant peripheral nerve sheath tumor Updated: 08/07/2020 © Jun Wang, MD, PhD General features AKA: Malignant schwannoma, neurofibrosarcoma Commonly associated with neurofibromatosis (NF) 1 May arise de novo More common in adults May have history of radiation exposure May recur, distant metastases common Clinical presentations Deep seated tumor associated with major nerves Commonly location: Neck, forearm, lower leg, buttock Key morphological features Hyperchromic spindle cells Markers Positive for S-100, CD56 Negative for EMA, keratin (different from synovial sarcoma) Treatment Excision Radiation Chemotherapy Back to soft tissue tumors Back to contents

Liposarcoma Updated: 08/07/2020 © Jun Wang, MD, PhD General features Most common soft tissue sarcoma of adults More common in 40 + age Usually deep site, especially retroperitoneal Recurrence common Clinical presentations Soft mass Single or multiple Key morphological features Features of adipose tissue differentiation Cytological atypia Lipoblast : Cells with irregular dense nuclei and multiple intracellular lipid vacuoles Markers Positive for S-100, negative for HMB-45  WHO classification Atypical lipomatous tumour/well differentiated liposarcoma Dedifferentiated liposarcom a Myxoid liposarcoma/round cell liposarcoma Pleomorphic liposarcoma Liposarcoma, not otherwise specified Treatment Surgery Post-surgery radiation therapy Back to soft tissue tumors Back to contents

Lipoma Updated: 08/07/2020 © Jun Wang, MD, PhD General features Most common soft tissue tumor Benign Clinical presentations Single or multiple Soft mass Key morphological features Morphologically normal mature adipose tissue Fine fibrous capsule grossly or microscopically Treatment Excision Back to soft tissue tumors Back to contents

Leiomyosarcoma   Updated: 08/07/2020 © Jun Wang, MD, PhD General features Malignant tumor of smooth muscle Commonly in uterus, skin, subcutis, deep soft tissue and GI Third most common retroperitoneal sarcoma after liposarcoma and undifferentiated pleomorphic sarcoma Aggressive clinical behavior Most common metastasis site: lung Clinical presentations Mass Symptoms depending on location Key morphological features Large tumor Hypercellular, hyperchromic spindle cells Pleomorphic cells, usually marked cytological atypia Necrosis, active mitosis, atypical mitosis Markers Positive for desmin, smooth muscle actin Genetic abnormalities Complex, commonly p53 mutation and p16 overexpression Treatment Excision Chemotherapy Radiation Poor prognosis indicators Retroperitoneal, mesenteric or other deep location > 5 cm, except uterus > 65 years C-myc expression Back to soft tissue tumors Back to contents

Leiomyoma   Updated: 08/07/2020 © Jun Wang, MD, PhD General features Benign tumor of smooth muscle Commonly in uterus, skin, subcutis, deep soft tissue and GI If multiple: Leiomyomata Clinical presentations Mass Uterine leiomyoma may cause dysfunctional uterine bleeding or lower abdomen pressure-related symptoms Key morphological features Well circumscribed firm mass Bulging trabecular cut surfaces Bundles or fascicles of spindled cells with minimal atypia Cigar shaped nuclei Usually no necrosis, no mitosis Markers Positive for desmin, smooth muscle actin Genetic abnormalities HMGIC, HMGIY, MED12 for uterine leiomyoma Treatment Excision Back to soft tissue tumors Back to contents