A female newborn, delivered at term after uncomplicated pregnancy, was hospitalized a few days after birth for the presence of slight facial asymmetry due to a space-occupying lesion in the left parotid region. Clinical examination demonstrated a well-demarcated ovoid mass, medially located to the angle of the mandible, which was mildly hyperechoic and solid at ultrasound examination, with a maximum diameter of 2.7 cm (Fig. ). Lymph nodes enlargement was detected bilaterally in the neck and interpreted as reactive in nature. Color-doppler examination showed multiple vascular proliferations, possibly arterial in nature, and subsequent CT-scan and NMR examinations confirmed the solid nature of the lesion, which also showed increased signal after contrast enhancement. Anatomically, the mass was sharply defined and in continuity with the postero-inferior area of the superficial lobe of the left parotid. Adjacent osseous and soft tissue structures were mildly compressed, as were the overlaying skin and subcutis.
Ultrasound examination demonstrated a well-demarcated ovoid mass, medially located to the angle of the mandible, solid and mildly hyperechoic, with a maximum diameter of 2.7 cm
The above data were suggestive for a benign lesion and, in consideration of the age of the patient, strict follow-up was advised with semi-annual clinical and ultrasound examination. The lesion slowly grew over the next 3 years up to the maximum diameter of 3.1 cm when the patient reached the age of 3 and surgery was recommended.
Subsequently, the patient underwent superficial parotidectomy and remained well and free of disease over the next 2 years.
The surgical specimen consisted of a 3.2 × 3.0 × 2.4 cm red mass containing distinct white-yellowish striations (Fig. ). The mass was well-circumscribed and showed distinct lobular architecture.
The surgical specimen consisted in a 3.2 × 3.0 × 2.4 cm red mass containing distinct white-yellowish striations. The mass was well-circumscribed and showed distinct lobular architecture
It was fixed in 10% neutral buffered formalin for 24 h, embedded in paraffin, cut and stained with hematoxylin–eosin (H&E) and Gomori’s reticulin.
Consecutive sections, collected on poly-l-lysine-coated slides, along with appropriate positive controls (detailed in Table ), were used for the immunohistochemical detection of the antigens listed in Table , with an avidin-biotin peroxidase (ABC) method. All sections were subjected to an epitope retrieval procedure in boiling 0.01M citrate buffer, pH 6.0, under 4 cycles of 5 min. irradiation in a microwave oven, operating at 750 W. All the subsequent incubations with primary antibodies took place for 2 h at room temperature in an automated immunostainer (Autostainer Dako, Glostrup, Denmark).
List of the antibodies (all raised in mouse, with the exception of S-100 protein, which was raised in rabbit) used to immunocharacterize sialangiolipoma
Negative controls were obtained by substituting the primary antibodies with non-immune rabbit or mouse sera, and consistently lacked any immunostaining.
At low power magnification thin fibrous septa subdivided the lesion in distinct lobules showing similar histological structure (Fig. ). Variably sized salivary lobules composed of both acinar and ductal structures were evident throughout the mass and were separated from each other by variable amounts of fibrous connective tissue containing blood vessels of different diameter. Groups of mature and mono-vacuolated adipocytes were sparse throughout the lesion. The glandular structures were composed by acinar cells surrounded by a basal layer of spindled and cuboidal cells, morphologically consistent with myoepithelial and basal cells. A structured ductal system departed from the acini, with evidence of intercalated, striated, intra- and inter-lobar ductal differentiation (Fig. ).
Fig. 3 At low power magnification the lesion shows distinct lobular architecture. Variably sized salivary lobules are evident throughout the mass and are separated from each other by variable amounts of fibrous connective tissue. Groups of mature adipocytes (more ...)
Fig. 4 The glandular structures are composed by acinar cells surrounded by a basal layer of spindled and cuboidal cells. A structured ductal system departs from the acini, with evidence of intercalated and striated ducts (Haematoxylin–Eosin, 100×) (more ...)
A fibrous stroma was interposed among acinar and ductal structures, containing variably sized blood vessels, that apparently dissociated and replaced the glandular structures to varying extents: some parotid lobes, particularly those peripherally located, were almost entirely composed by acinar/ductal structures while others, especially in the centre of the mass, were predominantly composed by fibroconnective tissue and blood vessels with evidence of scattered and dispersed acinar/ductal structures.
The blood vessels most frequently were of capillary size but venular, arteriolar and cavernous vessels were present as well and were randomly distributed within the lesion (Fig. ).
Fig. 5 The stromal component interposed among acinar and ductal structures contains variably sized blood vessels. These most frequently are of capillary size but venular, arteriolar and cavernous vessels are present as well (Haematoxylin–Eosin, 100×) (more ...)
The amount of adipose tissue was extremely variable, from isolated mature lipocytes, sometimes laying in close proximity with the acinar structures, to distinct lobules of mature fat tissue.
Mitotic activity, necrosis or invasive growth were not detected.
A distinct layer of muscle actin- and calponin-immunoreactive myoepithelial cells (Fig. ) was evident around the acinar structures and striated and intercalated ducts while cytokeratin 34βE12-positive cells were detectable in a basal location within the acini and the ductal structures.
A distinct layer of calponin immunoreactive myoepithelial cells is evident around the acinar structures and striated and intercalated ducts (ABC technique, anti-calponin, 200×)
The vascular component showed consistent CD31 immunoreactivity in the endothelial layer and muscle actin and calponin immunoreactivity in the vessel walls. Adipocytes disclosed consistent S-100 protein positivity.