Sclerosing Hemangioma (Pneumocytoma)

Key Facts

Terminology

Pneumocytoma

Etiology/Pathogenesis

Tumor appears to have pneumocytic differentiation, yet histogenesis remains unclear

Clinical Issues

Incidence
- More common among women
- Tumor is more common in 4th and 5th decade of life

Macroscopic Features

Well-circumscribed but not encapsulated
- More often peripheral tumor
- Rarely central tumor

Microscopic Pathology

Biphasic
Solid
Papillary
Sclerotic
Hemorrhagic
Combination of patterns more often present in same tumor

Top Differential Diagnoses

Papillary carcinoma
- SH lacks nuclear atypia &/or increased mitotic activity
- Presence of biphasic cellular population characteristic of SH

Gross photograph of sclerosing hemangioma shows a well-circumscribed intrapulmonary tumor mass

. The tumor has been bisected and shows a fleshy, focally hemorrhagic surface.

Sclerosing hemangioma shows dilated vascular spaces

filled with blood, giving the appearance of a true vascular tumor.

TERMINOLOGY

Abbreviations

Sclerosing hemangioma (SH)

Synonyms

Pneumocytoma

Definitions

Benign neoplasm of pneumocyte derivation

ETIOLOGY/PATHOGENESIS

Histogenesis

Tumor appears to have pneumocytic differentiation, yet histogenesis remains unclear

CLINICAL ISSUES

Epidemiology

Incidence
- Tumor of rare occurrence
Age
- 4th or 5th decade of life
Gender
- More common among women

Presentation

Asymptomatic
Cough
Chest pain
Hemoptysis

Treatment

Surgical approaches
- Complete surgical resection

Prognosis

Excellent
In unusual cases, tumor metastasizes to lymph nodes

MACROSCOPIC FEATURES

General Features

Well-circumscribed but not encapsulated
- More often peripheral tumor; rarely central location

Size

1-8 cm in diameter

MICROSCOPIC PATHOLOGY

Histologic Features

Solid
Papillary
Sclerotic
Hemorrhagic
Combination of patterns often present in same tumor

Cytologic Features

Small cells with hobnail nuclei lining papillary structures
Monotonous population of round/polyclonal cells with clear cytoplasm in solid areas

DIFFERENTIAL DIAGNOSIS

Papillary Carcinoma

Marked nuclear atypia &/or increased mitotic activity
Presence of biphasic cellular population is characteristic of SH
Carcinoma and SH show positive staining for similar markers, including keratin and TTF-1
Increased proliferative activity (↑ Ki-67 stain)

Mesothelioma