Teaching Case

A 53-year-old woman complained of bilateral parotid swelling, slight pain and xerostomia for the last six months. Her symptoms were progressive. Other than a history of total hysterectomy due to endometriosis, there was no medical history of note. Serologic tests (anti-Ro, anti-La, c-ANCA) were negative for autoimmune disease.

The patient underwent ultrasound examination in another department and was referred to us for whole body MRI (neck, thorax, abdomen). MRI of the neck (Fig. 1 and 2) revealed bilateral multiple parotid nodules, high signal on T2W, intermediate to low signal on T1W and with no significant enhancement. Prominent posterior triangle lymph nodes were also seen. US (Fig. 3 and 4) subsequently demonstrated hypoechoic (solid appearing) nodules, and a few intraparotid lymph nodes with fatty hilum. Some of these nodules contained microcalcifications. Parenchymal blood flow was increased. The submandibular glands were mildly affected, with increased vascularity and heterogeneous echotexture. There was no involvement of other organs (on CXR and chest/ abdominal MRI). A diagnosis of sarcoidosis was made on the basis of blood studies (elevated serum angiotensin-converting enzyme and alkaline phosphatase), negative labial gland biopsy and fine needle aspiration cytology (confluent non-necrotising granulomas with epithelioid cells and large multinucleated giant-cells).

Sarcoidosis is a chronic multisystem granulomatous disease with a special predilection for the lungs and hilar lymph nodes. It commonly affects young adults and particularly black women, 30 to 40 years old [1]. Involvement of the parotid glands occurs in 6% of patients [2].

Salivary glands are quite susceptible to sarcoid [3]. Major salivary gland swelling involving both parotid glands and at times the submandibular glands, can be present. The glands tend to be firm, only slightly painful and do not fluctuate in size when eating.

Parotid involvement includes bilateral solid lesions (representing granulomas) or less commonly takes a diffuse form [1]. On ultrasound examination there may be multiple solid hypoechoic areas in enlarged or normally-sized glands, or diffuse low echogenicity. Parenchymal blood flow may be increased. The nodules may contain calcific foci, evidence of chronic inflammation [4]. Multiple bilateral enlarged cervical lymph nodes can also be seen.

MR findings are quite similar. There may be multiple benign-appearing non-cavitating masses, which are hyperintense on T2W and hypointense on T1W images and represent non-caseating granulomata [4]. In the diffuse form parotid glands are symmetrically enlarged and show increased signal intensity on T2-weighted images with intense enhancement following administration of gadolinium [1].

The main differential diagnosis is Sjogren's disease, as initially suspected. However, serologic tests and labial gland biopsy were not compatible with this diagnosis. In addition, the imaging features of Sjogren's are slightly different; the underlying pathological process involves diffuse lymphocytic infiltration, sialectasis and large cyst formation [5]. Furthermore, Sjogren's may have a "salt and pepper" or "honeycomb" appearance throughout the gland with multiple areas of high and low signal intensity, representing cysts and fat deposition respectively [6]. The fatty areas are suppressed on short tau inversion recovery (STIR) imaging. This was not seen in our case.

Wegener's granulomatosis is a further differential diagnosis, but is rare and does not occur as an isolated finding. Moreover, c-ANCA were not found on serologic testing [1].

The diagnosis of sarcoidosis requires three components: the presence of clinical and radiographic findings consistent with a diagnosis of sarcoidosis, non-caseating granulomata obtained from one or more sites, and exclusion of other granuloma-forming diseases using appropriate histochemical, microbiologic and serologic tests [3]. Non-caseating granulomata with a core of epithelioid and giant cells and a periphery of lymphocytes and fibroblasts are seen. Blood studies often show elevated calcium and alkaline phosphatase levels, increased serum angiotensin converting enzyme (ACE) levels, and hypergammaglobulinaemia.