Dear Editor

Warthin tumor (WT) of the salivary gland (so called papillary cystadenoma lymphomatosum or adenolymphoma) is a benign neoplasm of the salivary gland epithelium with a proliferative epithelial component associated with a variably prominent stroma.[1] As reported by Saxena [1], histogenesis of this entity is very controversial. WT and malignant lymphoma are rarely associated, and most are examples of involvement of the lymphoid stroma of WT by a disseminated lymphoma.[1] Less commonly, malignant lymphomas are first detected in the lymphoid stroma of WT.[1] Most of reported cases are low-grade follicular lymphoma.[2] To the best of our knowledge no well-documented cases of nodal marginal B-cell lymphoma arising from WT in the same site have been described so far.

We report the case of a 74-year-old man with a fast enlarging right parotid mass. On physical examination the mass was firm, painless, developed in the lower pole of the parotid gland. A partial parotidectomy was performed. At gross examination, the tumour measured 4.2 x 3.1 x 1.7 cm and cut surface revealed an irregular, brown mass replacing parotid gland. Histologically, the tumour was composed of cystic spaces with typical bilayered oxyphilic epithelium.(Figure 1A) This epithelium was surrounded by malignant lymphoma characterized by diffuse infiltrate of small to medium lymphoid cells composed of centrocyte-like B-cells, plasmocytoid B-cells, scattered centroblast and immunoblast-like cells.(Figure 1B) No germinal center, lympho-epithelial lesion or necrotic areas were observed. The immunohistological study demonstrated a phenotypical profile (CD20/CD79a/BCl-2+; CD3/CD5/CD10/CD21/cycline D1-) consistent with marginal zone B-cell lymphoma. (Figure 1C, D)

On the basis of morphological and immunohistological findings, a diagnosis of nodal marginal zone B-cell arising of WT's lymphoid stroma was established. A thorough staging examination, including cervical, thoracic and abdominal scans revealed no evidence of other peripheral lymph nodes involvement. All laboratory test results were normal except a small monoclonal serum protein and mild lymphocytosis which slowly increased since 2004. The immunophenotypage showed a monotypic B-cell lymphoid population with moderate Lambda light chain expression. No bone marrow biopsy was done. Because of localised disease, no treatment was started. At this time, the patient has been followed-up for 21 months, without evidence of recurrent tumoral syndrome.

Distribution of WT localization (parotid glands and periparotid lymph node and its absence from other salivary tissue lacking incorporated lymph node) seems to show that WT's histogenesis results from heteropic salivary ductal inclusions in intra- or peri-parotid lymph nodes.[3] This theory explains that most lymphomas arising of WT are follicular lymphomas, which are the most frequent of systemic lymphomas.[4] No marginal zone B-cell lymphoma arising of WT was yet reported. Only one case reported in the same parotid gland the association of two differents lesions: a WT and an extranodal mucosa-associated lymphoid tissue lymphoma.[4] Extranodal marginal zone B-cell lymphoma is probably the most common type of lymphoma truly of salivary gland origin [3] and should be distinguished from nodal lymphomas presenting in intraparotid lymph nodes which usually carry a worse prognosis. [5] Most of cases occur in women, particulary aged over 50, with a history of Sjögren's syndrome or other autoimmune disease. In our case, no history of Sjögren's syndrome or other autoimmune disease was mentioned. Futhermore, the absence of lympho-epithelial lesion is a supplementary argument for the nodal origin of the marginal zone B-cell lymphoma. This finding confirm also WT's histogenesis. Nodal marginal zone B-cell lymphomas arising of intraparotidal Warthin's tumour are real nodal lymphomas and require a thorough staging examination.

References

1. Saxena A., Memauri B, and Hasegawa W. Initial diagnosis of small lymphocytic lymphoma in parotidectomy for Warthin tumour, a rare collision tumour. J Clin Pathol. 2005;58:331-333.

2. Park CK, Manning JT, Battifora H, Medeiros LJ. Follicle center lymphoma and Warthin tumor involving the same anatomic site. Report of two cases and review of the literature. Am J Clin Pathol. 2000;113:113-119.

3. Marioni G, Marchese-Ragona R, Marino F et al. MALT-type lymphoma and Warthin's tumour presenting in the same parotid gland. Acta Otolaryngol. 2004;124:318-323.

4. Isaacson PG, Müller-Hermelink HK, Piris MA et al. Extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma). Jaffe ES, Harris NL, Stein H, Vardiman JW eds. WHO Classification Tumours of haematopoietic and lymphoid tissues. Lyon: IARC Press, 2001:157-160.

5. Simpson RHW, Sarsfield PTL. Benign and malignant lymphoid lesions of the salivary glands. Current Diagnostic Pathology. 1997;4:91-99.