The inflammatory lesions in Küttner's tumor may occur on one side or both sides, predominantly involving the submandibular gland, but is also known to occur in other major and minor salivary glands, including the parotid gland. Overall, salivary gland tumors are relatively rare, with approximately 2.5–3 cases per 100,000 people per year seen in the Western world; however, salivary gland malignancies account for 3–5% of all head and neck cancers. However, salivary tumors show a great deal of morphological diversity, as well as variations in the nature of the lesion : approximately 20% to 25% of parotid tumors, 35% to 40% of submandibular tumors, and more than 90% of sublingual gland tumors are malignant. This situation underscores the diagnostic challenges in respect of Küttner's tumor; despite being benign, this condition mimics the clinical appearance of malignancy in the salivary gland. The swollen masses of Küttner's tumor are generally painful, and patients are advised surgical resection of a part or whole of the glandular tissue upon suspicion of possible malignancy. It is only upon post-surgical histopathology of the excised mass that the diagnosis of Küttner's tumor is definitively made.
Histological features
The histopathological features that characterize Küttner's tumor include:
Heavy infiltration of the glandular tissue by lymphocytes as well as plasma cells.
The cause and pathogenesis of this chronic condition are not very well understood. Several factors have been postulated:
Formation of a hard salivary calculus or sialolith by accumulation of calcium salts in the duct of the salivary gland. This has been proposed as the most common cause for Küttner's tumor of the submandibular gland, with sialoliths observed in an appreciable proportion of cases. However, sialolith involvement may not be found in many cases.
Abnormalities of the salivary gland ducts leading to excessive accumulation or retention of ductal secretions, which can excite chronic inflammations.
Immune, especially autoimmune, cause - which has gained steam, given the observation that the tissue of the glands is overrun with lymphoid immune cells and fibrous connective tissue, as well as corroboration from markedly similar lesions seen elsewhere in the body. The presence of abundant Immunoglobulin G4 associated with Plasma cells infiltrating into the salivary glands, as well as increased serum IgG4 concentration, has been noted with patients with Küttner's tumor.
This chronic condition is primarily observed in adult patients. However, Küttner's tumor, with prominent immunopathological features, has been described in an 11-year-old boy in Brazil in 2012.
Diagnosis
Given the difficulties of a definitive pre-operative diagnosis, the clinical entity of Küttner's tumor has so far remained significantly under-reported and under-recognized. In recent times, armed with a better understanding of the occurrences and observable features of this condition, surgeons are increasingly depending upon pre-operative ultrasonography along with Fine-needle aspiration cytological examinations to make an accurate presumptive diagnosis, and according to one estimate, about 44% of patients undergoing submandibular resection are found to have this condition. In the ultrasonogram, Küttner's tumor is characterized by a diffuse, heterogeneous zone of echo-shadows. The FNAC finds cells greatly reduced in number along with scattered tubular ducts against a backdrop of lymphoplasmacytic infiltration and fibrous depositions. There may be a reduced but moderate number of cells and ducts enveloped in fibrous sheaths, as well as fibrous proliferation of the gland's septa. The cytologic findings by themselves may not be specific, and the diagnosis requires adjunct consideration of both the ultrasonogram and clinical presentation. Application of magnetic resonance imaging has been tried to non-invasively examine the morphological variations in Küttner's tumor and differentiate them from those seen in malignant tumors; while MRI findings of the affected tissue and the pattern of cellular infiltration may offer some diagnostic clues for this condition, so far the results have been inconclusive.
Existing treatment
Standard, and most effective, therapy to date is glandular sialadenectomy, which is associated with fairly low operative morbidity; however, in recent times, the administration of steroid has been considered favorably, and may be useful in younger patients or those who refuse surgery.
