Salivary duct carcinoma is a distinctive primary neoplasm of the major salivary gland first described by Kleinsasser et al in 19681. The term was selected because of its resemblance to ductal carcinoma of the breast. It is characterized by aggressive behavior with early metastasis, local recurrence and significant mortality. Nearly 85% of cases occur in the parotid gland followed by submandibular gland2. The tumor has predilection for older men in the 6th to 7th decades of life3. A number of patients experience facial nerve palsy or paralysis and/or pain, and have cervical lymphadenopathy on presentation1. Familiarity with this entity is necessary to avoid false interpretation.
A 40 year old Hindu male who had a 15 year history of smoking presented with a gradually increasing painless swelling on the left parotid region. On examination an 8 × 6 cm swelling was observed the A single Level II mobile lymph node of size < 1 cm was palpable. There was no facial palsy.
An ultrasonograph of the parotid region performed previously revealed a well defined hypoechoic mass (4.7 × 3.9 cm) with lobulation occupying the left temporomandibular joint with adjacent hypoechoic areas of varying sizes: 1.9 × 1.6 cm, 1.4 × 1.5 cm, and 1.1 × 1.2 cm. It was interpreted as a parotid mass. Fine needle aspiration cytology (FNAC) from the left parotid gland was done and reported as a pleomorphic adenoma. However, FNAC from the submandibular lymph node comprised of blood only.
A repeat FNAC at our institute (Figure 1) showed moderately cellular aspirates with few clusters of normal salivary gland tissue along with epithelial cells showing overcrowding, with a mild-to-moderate pleomorphic population of medium sized cells with the vesicular nuclei having evenly distributed chromatin without conspicuous nucleoi. Cytoplasm was eosinophilic with ill defined borders. It was interpreted as an epithelial neoplasm.
A CT scan of the face and neck showed that the left parotid gland had enlarged in size (9 × 6 × 4 cm), involving deep and superficial lobes, with replacement of normal glandular architecture by homogenous soft tissue. The adjacent musculo-fascial planes were preserved. Multiple enlarged discrete lymph nodes in the left parotid were noted. The left internal jugular vein was compressed and no intraluminal thrombosis was seen.
In order to reach a diagnosis, a frozen Level II lymph node was performed. (Figure 2) On frozen section, the lymph node architecture was not seen. Cells were singly scattered having scanty cytoplasm, enlarged hyperchromatic nuclei and condensed chromatin. It was not possible to identify the type of malignancy and was therefore reported as a high grade malignant neoplasm.
On routine histopathology, neck nodes were resected. Six out of seven lymph nodes showed a metastatic neoplasm comprising of sheets and lobules of pleomorphic cells with coarse clumped chromatin separated by fibrous septa. Mitotic activity increased, rosette formation was noted, and it was reported as a poorly differentiated carcinoma with basaloid phenotype. The presence of a high mitotic rate and of focal large, polypoid nuclei suggested an origin from the sebaceous gland.
Finally, a total parotidectomy with modified neck dissection was performed. On gross examination the specimen comprised of:
– Single gray soft tissue piece with skin tag (15 × 14 × 4 cm).
– Skin (4.5 × 2 cm).
– Salivary glands (4 × 2 × 2 cm) were grossly unremarkable.
– Multiple lymph nodes at level II & III – (1.5 to 5.5 cm).
– A deep lobe parotid gland.
– Several gray soft tissue pieces (7 × 7 × 3 cm) with a level I lymph node.
– A single gray soft tissue piece (4 × 4 × 1 cm) (Figure 3).
Microscopic analysis (Figure 4, Figure 5) showed that the tumor comprised of slightly pleomorhic ovoid cells with vesicular nuclei arranged in sheets and a trabecular pattern separated by fibrous septa. Mitotic activity was not increased. Focal area showed an acinar and comedo pattern. Perineural and lymphovascular invasion were seen. Infiltration into the salivary gland tissue was noted. Eight out of ten lymph nodes showed metastatic carcinoma. In view of metastasis to a lymph node, a diagnosis of high grade malignant epithelial neoplasm was suggested, which was later confirmed via immunohistochemistry as salivary duct carcinoma.