This is a tumor of uncertain nature, seen only in young
infants and
is characterized
clinically by severe and often fatal arrhythmias.
Present knowledge of these lesions
consider them as a form of “cardiac hamartoma”.
This lesion is not a tumour of Purkinje cell
but a cardiomyopathy of unknown etiology and pathogenesis, the
possible suggestions are:
- Persistence of early developmental
stage of myocytes with their change into oncocytes . Viral infection as
rubella, in early stage of gestation may be a possible cause .
- With advances of electrophysiologic mapping, attention is drawn to the increasing
incidence of ventricular tachycardia in infants and its relevance to
Purkinje cell tumours .
Gross features:
These are circumscribed or
diffuse lesions, yellowish-white in color, and usually in the subendocardial or subepicardial location. They usually involve
ventricles but atrial myocardium may also be involved.
Microscopic
features: The
appearance
is distinctive, showing clusters or sheaths of swollen myocardial
cells (twice the normal size) with granular eosinophilic, often
vacuolated cytoplasm. Mitotic figures are absent.
Note:
Histiocytoid cardiomyopathy is considered to be the result of
hamartoma-like aggregations of cardiac myocytes with features similar
to those of oncocytes.
This syndrome
is likely caused by prenatal myocardial or systemic (viral?) injury.
It has
been reported in a study that there is a high prevalence of anomalies
involving the nervous system and eyes and of oncocytic cells in
various glands.
Evidence is
presented to exclude the possibilities that the disorder represents a
developmental anomaly of the atrioventricular conduction system, a
multifocal tumour of Purkinje cells, a developmental arrest of cardiac
myocytes, and a diffuse type of mitochondrial cardiomyopathy.
The close
association of the lesion with cardiac arrhythmias in very young
infants is of special interest to pathologists. Histiocytoid
cardiomyopathy is a cause of sudden death in infancy.
Surgical
excision of nodules of histiocytoid cells can result in clinical
remission. |
