Page 268 - Concise Pathology for Exam Preparation ( PDFDrive )

10 Blood Vessels 253

Morphology of KS: Three stages are identified:
• Patch stage: Pink to red, solitary to multiple macules in the distal lower extremities
Microscopy: Dilated, irregular and angulated blood vessels lined by endothelial cells
with an interspersed infiltrate of lymphocytes, plasma cells and macrophages
• Plaque stage: Patch lesion over time converts into larger, violaceous and raised
plaques
Microscopy: Dilated, jagged and dermal vascular channels lined by plump cells accom-
panied by perivascular aggregates of spindle cells; scattered between vascular chan-
nels are haemosiderin-laden macrophages, lymphocytes, plasma cells and pink hya-
line globules of uncertain origin
• Nodular stage: At a later stage, lesions become distinctly nodular and may be accompa-
nied by involvement of lymph nodes and viscera.
Microscopy:
• Sheets of plump proliferating spindle cells in the dermis and subcutaneous tissue
• Small scattered slit-like vessels in a background containing RBCs and pink droplets
• Marked haemorrhage, haemosiderin-laden macrophages and lymphocytes
Pathogenesis of KS
• Ninety-five percent of KS lesions are infected with KSHV (KS-associated herpes virus
called human herpes virus) or HHV-8.
• Immunosuppression is an important cofactor in pathogenesis and clinical expression
of the disease.
• KSHV proteins disrupt the control of cellular proliferation and prevent apoptosis of
endothelial cells, through the production of P53 inhibitors and a viral homologue of
cyclin D.
2. Hemangioendothelioma
(a) Group of vascular neoplasms showing histological features intermediate between
benign haemangioma and frankly malignant angiosarcomas.
(b) A representative of this group is epithelioid hemangioendothelioma. It occurs in
medium-sized and large veins in soft tissue (well-defined vascular channels are
conspicuous and tumour cells are plump epithelial like).

Q. Enumerate the malignant vascular tumours and write
briefly about them.

Ans. Malignant vascular tumours are of two main types:
1. Hemangiopericytoma
(a) Heterogeneous group of neoplasms with a fleshy or spongy consistency and thin-
walled branching, staghorn vascular pattern. It is derived from ‘pericytes’.
(b) Two-thirds of these tumours have a benign course; one-third are malignant.
(c) Presence of necrosis, high mitotic rate and nuclear pleomorphism are associated
with aggressive behaviour.
2. Angiosarcoma
(a) Malignant vascular tumour derived from endothelium.
(b) Angiosarcomas vary from highly differentiated tumours to those resembling epithe-
lial neoplasms like carcinomas and melanomas.
(c) Stain positive for CD31, CD34 or VW factor.
(d) Seen in older adults; most commonly in skin, soft tissue, breast and liver.
(e) May arise in the setting of lymphoedema, radiation exposure or foreign material
introduced into the body iatrogenically or accidentally.
(f) Local invasion and distal metastatic spread is common. Outcome is poor with very
few surviving 5 years.

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