Vascular Tumours

Overview

Most benign vascular tumours = malformations/hamartomas (no true neoplastic potential); boundary with true benign tumours not sharp. Spectrum: benign → intermediate → malignant.

A. Benign/hamartoma

Haemangioma: common, infancy/childhood, face/mucosa.

• Capillary — commonest, red-purple lobulated, birth/early childhood (strawberry mark, port-wine mark). Histology: capillary-sized blood-filled lobules, plump endothelium+pericytes. REGRESSES spontaneously.
• Cavernous — red-blue spongy (1-2cm), skin(face/neck)>mucosa>liver/spleen. Histology: large thin-walled blood-filled spaces, flattened endothelium. RARELY involutes (opposite of capillary type).
• Granuloma pyogenicum — exophytic red nodule, post-traumatic; granuloma gravidarum = pregnancy variant (regresses postpartum). Histology: like capillary haemangioma + oedema/inflammation (granulation-tissue-like).

Lymphangioma: congenital, lymphatic counterpart of haemangioma.

• Capillary (simplex) — small, head/neck/axilla, lymph-filled capillary spaces + lymphoid aggregates.
• Cavernous — commoner, head/neck/axilla. Cystic hygroma = large cystic variant, neck deformity. Benign but hard to excise (infiltrates adjacent tissue).

Glomus tumour: benign, glomus cells (AV shunt/Sucquet-Hoyer anastomosis). Fingers/toes under nail. EXTREMELY PAINFUL (nerve fibres in stroma explain this). Small vessels + glomus cell nests.

AV malformation: artery-vein communication, NO intervening capillary bed. Congenital (thick-walled, hyalinised/calcified) vs acquired (dilated thick veins).

Bacillary angiomatosis/peliosis hepatis: NOT a tumour — opportunistic Bartonella infection, HIV/AIDS with CD4<100/µl. Skin/bone (liver=peliosis hepatis). Responds to ANTIBIOTICS — key distinguishing practical point.

B. Intermediate

Haemangioendothelioma: true endothelial tumour, behaviour between haemangioma and angiosarcoma. Skin/subcutaneous near medium-large veins (cerebellar version = haemangioblastoma). Multilayered endothelial proliferation, variable mitoses.

C. Malignant

Haemangiopericytoma: pericyte tumour (cells external to capillary/venule endothelium). Lower limbs/retroperitoneum. Spindle pericytes OUTSIDE basement membrane, whorled (reticulin stain confirms). Local recurrence common, distant spread ~20%.

Angiosarcoma: skin/subcutaneous/liver/spleen/bone/lung/retroperitoneum, any age/sex. Hepatic form → PVC, arsenical pesticides, thorotrast (classic carcinogen link). Well-diff (clear channels) to poorly-diff (anaplastic, channels barely visible). Local invasion + lung/distant mets. Lymphangiosarcoma = similar tumour in long-standing lymphoedema.

Kaposi’s sarcoma: HIV/AIDS-associated malignant angiomatous tumour. 4 forms:

Pathogenesis: opportunistic, spindle cells (endothelial+smooth muscle features). HIV + HHV-8 (KSHV) association. Cytokines (IL-6, TNF-α, GM-CSF, bFGF, oncostatin M) drive it — explains ↑incidence in male homosexuals (activated immune system → more cytokines). ~1/3 patients get 2nd malignancy (leukaemia/lymphoma/myeloma) — supports immunoregulation defect.

Morphology same across all 4 forms: purple dome-shaped plaques. STAGE-dependent histology: early patch (nonspecific vascular spaces + inflammation + extravasated blood/haemosiderin) → late nodular (slit-like vascular spaces + spindle tumour cells, endothelial origin).

Course: classic = indolent, skin-confined, long survival. Endemic/epidemic = rapid, widespread, high mortality.

Clinical relevance

Capillary (regresses) vs cavernous (doesn’t) haemangioma = opposite natural histories directly affect clinical decision (watch vs treat), not just microscopic labels. Bacillary angiomatosis mimics vascular neoplasm but is a TREATABLE bacterial infection — high-stakes distinction in HIV patients, missing it = missing a curable diagnosis. Haemangiopericytoma vs haemangioendothelioma = same reticulin stain, opposite question (pericytes outside vs endothelium proliferating) — interpretation is the actual testable point. Kaposi’s 4 forms sharing IDENTICAL histology but very different behaviour = clearest example that morphology alone can’t predict prognosis — clinical context does as much work as biopsy. Hepatic angiosarcoma’s carcinogen links (PVC/arsenic/thorotrast) = concrete testable occupational-exposure example.

Overview

Most benign vascular tumours are actually malformations or hamartomas (tumour-like lesions built from tissue native to the site, lacking true neoplastic growth potential) — the boundary between vascular hamartoma and true benign tumour is not sharp, so both are conventionally described together. A spectrum exists from benign, through intermediate-grade, to frankly malignant vascular neoplasms.

A. Benign Tumours and Hamartomas

Haemangioma

Common, especially in infancy/childhood; most often skin of the face and mucosal surfaces.

• Capillary haemangioma — the most common type; flat-to-elevated, red-purple, soft, lobulated lesions (a few mm to a few cm). Present at birth or early childhood (strawberry birthmark, port-wine mark); skin/subcutaneous tissue/oral mucosa most common, occasionally liver/spleen/kidney. Histology: well-defined but unencapsulated capillary-sized, thin-walled, blood-filled lobules, lined by plump endothelium with a surrounding pericyte layer. Many regress spontaneously within a few years.
• Cavernous haemangioma — single/multiple, discrete/diffuse, red-blue, soft, spongy (1–2 cm); skin (face/neck) most common, also oral/GI mucosa, liver, spleen. Histology: large, thin-walled cavernous spaces, partly/fully blood-filled, lined by flattened endothelium, scanty stroma. Rarely involutes spontaneously — the key contrast with the capillary type.
• Granuloma pyogenicum (“haemangioma of granulation tissue type”) — exophytic red nodule of skin/gingival mucosa, often post-traumatic; granuloma gravidarum is the pregnancy-associated variant that regresses after delivery. Histology: proliferating capillaries as in capillary haemangioma, but separated by abundant oedema and inflammatory infiltrate — resembling inflammatory granulation tissue rather than a “clean” vascular proliferation.

Lymphangioma

The lymphatic counterpart of haemangiomas; congenital.

• Capillary lymphangioma (lymphangioma simplex) — small (1–2 cm), circumscribed, slightly elevated; skin of head/neck/axilla, mucous membranes. Histology: capillary-sized, endothelium-lined, lymph-filled spaces with lymphoid aggregates.
• Cavernous lymphangioma — more common than the capillary type; head/neck/axilla. The large cystic variant, cystic hygroma, causes gross neck deformity. Histology: large dilated lymph-filled spaces, flattened endothelium, scanty stroma. Benign but often difficult to excise due to infiltration of adjacent tissue.

Glomus Tumour (Glomangioma)

An uncommon true benign tumour of contractile glomus cells (found at arteriovenous shunts — the Sucquet-Hoyer anastomosis). Classic site: dermis of fingers/toes under a nail; also gastric/nasal mucosa. Characteristically extremely painful — small (<1 cm), red-blue, painful nodules. Histology: small endothelium-lined vessels surrounded by nests/masses of round-to-cuboidal glomus cells; stroma contains non-myelinated nerve fibres (explaining the pain).

Arteriovenous (AV) Malformation

A direct artery-vein communication without an intervening capillary bed — congenital (thick-walled vessels, hyalinisation/calcification) or acquired (dilated, thick-walled veins predominate).

Bacillary Angiomatosis / Peliosis Hepatis

A tumour-like lesion — actually an opportunistic infection (gram-negative Bartonella) in HIV/AIDS with CD4+ counts below 100/µl. Skin and bone are the commonest sites; the liver-based counterpart is peliosis hepatis. Gross: variable-sized red skin papules. Histology: lobules of proliferating vessels lined by mildly atypical epithelioid endothelial cells, with mixed inflammatory infiltrate and neutrophilic nuclear debris. Responds to antibiotics — an important practical point distinguishing it from a true neoplasm requiring oncologic management.

B. Intermediate-Grade Tumours

Haemangioendothelioma

A true endothelial-cell tumour with behaviour intermediate between haemangioma and angiosarcoma. Found chiefly in skin/subcutaneous tissue near medium-large veins (the cerebellar counterpart is termed haemangioblastoma). Gross: well-defined grey-red polypoid mass. Histology: active multilayered endothelial proliferation around vessels, often obliterating the lumen, variable mitotic activity; reticulin stain delineates the proliferation pattern inside the basement membrane.

C. Malignant Tumours

Haemangiopericytoma

An uncommon tumour of pericytes (cells external to capillary/venule endothelium); more common in lower extremities and retroperitoneum, any age, 1–8 cm. Histology: capillaries surrounded by spindle-shaped pericytes outside the vascular basement membrane in a whorled pattern; reticulin stain confirms the pericytes’ extra-basement-membrane position, distinguishing it from haemangioendothelioma. High mitotic rate and necrosis possible. Local recurrence common; distant spread in ~20%.

Angiosarcoma (Haemangiosarcoma)

Malignant vascular tumour of skin, subcutaneous tissue, liver, spleen, bone, lung, retroperitoneum; either sex, any age. Hepatic angiosarcoma is specifically associated with polyvinyl chloride, arsenical pesticides, and thorotrast exposure — a classic carcinogen-association question. Gross: bulky, pale grey-white, poorly-marginated, with haemorrhage/necrosis/softening. Histology: spectrum from well-differentiated (proliferating endothelium around clear vascular channels) to poorly-differentiated (anaplastic, pleomorphic cells in solid clusters, channels barely identifiable). Locally invasive with frequent lung/distant metastases. Lymphangiosarcoma is the histologically similar tumour arising in long-standing obstructive lymphoedema.

Kaposi’s Sarcoma

A malignant angiomatous tumour (first described 1872), of major contemporary relevance through its association with HIV/AIDS. Four clinical forms:

Pathogenesis: an opportunistic neoplasm of immunosuppressed patients, showing excess proliferation of spindle cells with mixed endothelial and smooth-muscle features. Viral association with HIV and HHV-8 (KSHV); pathogenesis involves interplay of HIV-1 infection, HHV-8 infection, immune activation, and cytokine secretion (IL-6, TNF-α, GM-CSF, basic fibroblast factor, oncostatin M) — the higher incidence in male homosexuals is attributed to greater cytokine secretion by an activated immune system. Defective immunoregulation is further supported by a second malignancy (leukaemia, lymphoma, myeloma) occurring in about one-third of Kaposi’s sarcoma patients.

Morphology — identical across all four clinical forms: gross purple dome-shaped plaques/nodules (skin, gut, other organs). Histology is stage-dependent: early patch stage — nonspecific irregular vascular spaces with interstitial inflammatory cells, extravasated blood, haemosiderin; late nodular stage — characteristic slit-like vascular spaces containing RBCs, separated by spindle-shaped tumour cells of endothelial origin.

Clinical course: the classic form runs an indolent, skin-confined course with long survival; the endemic and epidemic forms are rapidly progressive with widespread cutaneous/visceral involvement and high mortality.

Clinical Relevance

• Capillary versus cavernous haemangioma’s opposite natural histories (capillary often regresses spontaneously; cavernous rarely does) is a genuinely practical distinction affecting whether a paediatric lesion is watched or actively treated — the histologic type predicts the clinical decision, not just the microscopic label.
• Bacillary angiomatosis mimicking a vascular neoplasm both clinically and morphologically, while actually being a treatable bacterial infection responsive to antibiotics, is a high-stakes distinction to get right in an HIV/AIDS patient — misreading it as a true tumour risks missing a curable diagnosis.
• Haemangiopericytoma and haemangioendothelioma are distinguished by the same technique (reticulin stain) applied to opposite questions — whether the tumour cells sit inside or outside the vascular basement membrane — making the stain’s interpretation, not just its use, the actual testable point.
• Kaposi’s sarcoma’s four clinical forms sharing identical histology but wildly different clinical behaviour is the clearest illustration in this topic that morphology alone cannot predict prognosis — clinical context (patient population, immune status) is doing as much diagnostic and prognostic work as the biopsy itself.
• Hepatic angiosarcoma’s specific carcinogen associations (PVC, arsenic, thorotrast) make it one of the few solid tumours with a well-established, directly testable occupational/iatrogenic exposure history, worth remembering as a concrete example when carcinogen-cancer links are asked generically.

No Rendered Diagram for This Topic

This topic is a grade-based classification (benign/hamartoma → intermediate → malignant) of otherwise unrelated entities, not a single shared mechanism — a rendered diagram would only redraw the classification table already in notes.md.

Hand-Draw Suggestion

Draw the reticulin-stain distinction by hand: two small circles representing a vessel lumen with endothelium, one showing spindle cells inside the basement membrane (haemangioendothelioma) and one showing spindle cells outside it in a whorled pattern (haemangiopericytoma) — this single visual captures the one point in the topic that is genuinely easy to mix up.