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Papillary Intralymphatic Angioendothelioma

Papillary intralymphatic angioendothelioma (PILA) is an uncommon, rarely metastasizing, superficial lymphatic vascular tumor, showing tufting and hobnail endothelial proliferations within lymphatic channel lumina, in a background of lymphatic vascular proliferation or lymphangioma.

Symptoms & Causes

Introduction

Papillary intralymphatic angioendothelioma is a rare lymphatic tumor characterized by hobnail endothelial proliferations within lymphatic channels, typically non-metastatic.

Reference
WHO Classification of Tumours Editorial Board. Soft tissue and bone tumours [Internet]. Lyon (France): International Agency for Research on Cancer; 2020 [cited 2024 09 11]. (WHO classification of tumours series, 5th ed.; vol. 3). Available from: https://tumourclassification.iarc.who.int/chapters/33.

Related Terminology
Not recommended: Dabska tumor; endovascular papillary angioendothelioma; hobnail hemangioendothelioma.

Subtype(s)
None

Symptoms

There is a slight female predilection (M:F ratio: ~0.7:1). PILA presents as a slow-growing asymptomatic cutaneous induration, plaque, or rarely nodule, often with unremarkable overlying skin. Radiology data are scant; intraosseous tumors are lytic and destructive and may be multifocal.

Localization

Most PILAs involve the proximal extremities, especially the buttock or thigh, and less commonly the distal extremities or trunk, head and neck, intra-abdominal sites, or parenchymal sites (including testis). Intraosseous locations are rarely reported.

Epidemiology

PILA is exceedingly rare, with < 50 reported cases.

Etiology

Unknown

Diagnosis & Treatment

Staging

Not clinically relevant

Pathogenesis

Unknown

Macroscopic Appearance

Tumors are ill defined and usually involve dermis and subcutaneous tissue. Grossly, greyish-white to pink streaks or cystic change in otherwise normal dermis and subcutis may be present, without hemorrhage or necrosis. Tumor size ranges from 1 to > 40 cm (mean: 7 cm).

Histopathology

PILA is an extensive, poorly delineated dermal and/or subcutaneous proliferation of lymphatic channels. A cavernous lymphangioma is often present nearby. The cavernous or slit-like lymphatic vascular channels are lined by columnar, matchstick-like, or hobnail endothelial cells. In addition, variable proliferations of intraluminal papillary tufts are noted, with hyaline cores and intermixed intraluminal lymphocytes with proteinaceous fluid. The lesional cells have eosinophilic cytoplasm and round uniform nuclei with indistinct nucleoli; they lack cytological atypia and mitoses. Tumor cells express pan-endothelial markers, such as CD31, ERG, and less often CD34, as well as lymphatic endothelial markers, such as podoplanin, VEGFR3, and PROX1.

Cytology

Not clinically relevant

Prognosis and Prediction

Most patients have excellent prognosis after complete excision. Very rarely, lymph node metastases and death from disease occur.

Clinical Features

Diagnostic Molecular Pathology

Not clinically relevant

Essential and Desirable Diagnostic Criteria

Essential: extensive infiltration of lymphatic vessels with stromal and intraluminal lymphocytes and proteinaceous fluid; intralymphatic, intraluminal hobnail proliferation of polarized matchstick-like columnar endothelial cells; expression of pan-endothelial and lymphatic markers.

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