Connective tissue benign & malignant neoplasms. Microscopic & gross pathomorphology
Benign connective tissue tumours
Such tumours originate from the connective tissue (fibrous, adipose tissues), the most common examples are lipoma, hemangioma, leiomyoma, chondroma and osteoma.
Gross, lipoma (6 cm, subcutis of the back): a well-circumscribed, thinly encapsulated mass with a soft, uniform, yellow fatty cut surface.
Image: “Lipoma gross” by Ed Uthman, MD, CC BY 3.0, via Wikimedia Commons.
Remember: lipoma is the most common benign soft-tissue tumour of adults: soft, yellow, encapsulated, made of mature fat cells. Its malignant counterpart, liposarcoma, is one of the most common sarcomas of adults, usually deep in the thigh or the retroperitoneum; its hallmark cell is the lipoblast, with fat vacuoles that indent (scallop) the nucleus.
- Chondroma
- Tumour cells are chondrocytes and resemble normal cells which produce cartilaginous matrix. There is a vascular axes within the tumour which differentiates it from normal hyaline cartilage
- Cavernous hemangioma (liver)
- Endothelial proliferation, tumour has large cavernous spaces, lined by endothelial cells, the spaces are connected by fibrous tissues.
Malignant connective tissue tumors
Known as sarcomas. Some types are mostly diagnosed in the young.
- Fibrosarcoma
- Originates from fibroblasts. Cells are arranged in short fascicles which split and merge, making it look like a fish bone. Poorly differentiated tumors have more atypical, giant, multinucleated cells with reduced collagen production.
- Osteosarcoma
- Tumour cells present osteoblastic differentiation. Highly anaplastic, some are giant and present atypical mitotic figures. Cells are irregular in structure and form, included in an osteoid matrix, possibly with cartilage and vessels.