Sarcoma Pathology

Histopathology

• Classified as tumors with differentiation toward features of any mesenchymal supportive or muscular tissue
• Vimentin typically is expressed in mesenchymal cell although under pathological conditions can be expressed in other cell types.
• The ratio of benign to malignant tumors is more than 100:1.
• Do not arise in situ; do not originate from benign soft tissue tumors
• Most common type MFH

Grading

Relative incidence of histologic types

Type	%
MFH	23
Fibrosarcoma	14
Liposarcoma	18
Leiomyosarcoma	10
Synovial cell	8
Neurosarcoma	8
Rhabdomyosarcoma	9
Unclassified	10

*Incidence variable with series

Grading

• Single most important factor in determining prognosis; requires experienced pathologist
• Cellular differentiation may be the most important histological variable in determining grade.
• Others important factors include pleomorphism, necrosis, mitoses, aneuploidy
• Several systems (Broders – 4 grade, AJCC – 3 grade, Memorial – binary).
• Pathologists disagree ~20% of the time on grade

For all tumor types, distant metastases increases steeply with grade (rare for grade 1; ~ 40% at 5yr for grade 3)
Markers/ Molecular Pathogenetics
None provides a definitive diagnosis
Pathologist must integrate information from H&E, EM, as well as molecular analysis

PNET (Not a sarcoma) three likely candidates

• neural crest
• primordial germ cells
• uncommitted mesenchymal cells
• neuron-specific enolase
• neurofilament
• HNK-l (Leu-7)
• S-100 protein,
• MB2 * t(11;22)(q24;q12)

Synovial Sarcoma

• Epithelial
• spindle cell
• Keratin - Epithelia
• vimentin + BCL-2 for spindle cells
• t(X;18)(p11:q11)

Rhabdomyosarcoma

• Striated muscle
• myoglobin
• t(2;13)(q35;q14)
• t(1;13)(p36;14)

Malignant Fibrous Histiocytoma

Familial adnomatous polyposis (FAP) & Desmoid Tumor (Aggressive Fibromatosis = Extra-abdominal desmoid tumor)

• Gardner’s (FAP) - is characterized by colorectal adenomatous polyps and soft and hard tissue neoplasms. The former may number in the hundreds to thousands.
• Both Gardner’s and FAP have APC gene.
• Desmoid Tumor is 10-15% of FAP patients and also share APC gene.
• Although desmoid tumors can arise in any skeletal muscle, they most commonly develop in the anterior abdominal wall and shoulder girdle.
• Retroperitoneal neoplasms are more common in familial polyposis coli and Gardner syndrome after abdominal surgery than in other conditions (Raynham, 1971).

Malignant schwannoma

• MIB-1/Ki6 proliferative index and PCNA (proliferating cell nuclear antigen)
• Tumors with a high proliferative status may have a short preoperative symptom duration, while tumors with a low proliferative status may have a long symptom duration.
• Neurofibromaoses (NF1) predisposed to optic nerve glioma, neurofibroma, neurobibrosarcoma, malignant schwannoma, astrocytoma, and pheochromocytoma.