Sebaceous lymphadenoma is a rare benign tumour which is histologically characterized by islands of epithelium showing sebaceous differentiation distributed in hyperplastic lymphoid tissue. Rawson and Horn 16
first described this benign neoplasm in 1950 and the name “sebaceous lymph-adenoma” was given by McGavran et al. in 1960 17
. The majority of these lesions occur in the parotid glands or periparotid lymph nodes 18
Sebaceous lymphadenoma of the parotid gland typically presents as a painless mass in patients over 50 years of age. Although it is known to occur equally in both sexes 10 12
both of our cases were male. Published case reports of sebaceous lymphadenoma do not often give a pre-operative diagnosis. In those cases where a pre-operative diagnosis was made on clinical, radiological or cytological grounds, they are found to be varied (Table ).
Examples of case reports with documented pre-operative diagnosis and final diagnosis of sebaceous lymphadenoma of parotid gland.
Sebaceous lymphadenoma was not correctly identified by pre-operative investigations in the majority of cases. Boyle and Meschter 12
, in a single case report, suggested that the FNAC findings in a sebaceous lymphadenoma were distinctive and accurately reflected the histological morphology, although the lesion is so rare that the diagnosis may be easily overlooked. In both of our cases, the FNAC reached did not indicate the correct diagnosis.
Two cases in the literature were diagnosed pre-operatively as pleomorphic adenoma 11 14
, the most common benign neoplasm of the parotid gland. The clinical presentation of sebaceous lymphadenoma is similar to that of pleomorphic adenoma i.e., a painless parotid swelling with no facial nerve involvement. In the Shukla and Panicker case 14
, the true diagnosis was sebaceous lymphadenoma plus concomitant squamous cell carcinoma. One of our cases was thought pre-operatively to be a Warthin’s tumour (adenolymphoma), which is the second most common benign parotid neoplasm, again with similar clinical features. Failure to make a correct pre-operative diagnosis of sebaceous lymph-adenoma did not alter the surgical management of these patients as non-urgent surgical excision is required for all these tumours. Malignancy was suspected in two cases. In the Assor case 5
, the pre-operative FNAC suggested mucoepidermoid carcinoma. In the Mayorga et al. case 9
, the sebaceous lymphadenoma was concomitant although the FNAC correctly diagnosed acinic cell adenocarcinoma.
On rare occasions, sebaceous lymphadenoma can transform into sebaceous lymph-adeno-carcinoma. This is an extremely rare malignant neoplasm and only four cases have been reported 19
. Synchronous occurrences of a sebaceous lymphadenoma with another neoplasm such as Warthin’s tumour 8 13
, acinic cell carcinoma 9
and squamous cell carcinoma 14
in the same parotid gland have been reported, but they are also rare.
FNAC is a useful technique in evaluating salivary gland lesions pre-operatively. Cytological diagnosis of a benign neoplasm by FNAC has been found to correlate with histological diagnosis of a benign neoplasm following excision in 83% of cases 20
. Failure to do so may be due to a variety of factors including operator inexperience, sampling error and inadequate samples. In both of our cases, FNAC correctly diagnosed benign tumours. However, when interpreting FNAC from parotid gland masses, these limitations of the procedure should be considered.
Sebaceous lymphadenoma is an unusual salivary gland neoplasm which is rarely correctly diagnosed pre-operatively in the parotid gland. Transformation into a malignant tumour is rare. FNAC identifies a benign process in the majority of patients who receive appropriate treatment on this basis. Although an uncommon tumour, it should be considered in the differential diagnosis of a solitary parotid mass.