Lymphoepithelioid lymphoma (Lennert's lymphoma) is a variant of peripheral T-cell lymphoma (1, 2), characterized by a high content of epithelioid cells, the presence of an atypical variant of Hodgkin and Sternberg giant cells, and an abundance of plasmocytes (3). It can be confused with various diseases that show a Lennert's pattern on histopathology, such as granulomatous lymphadenitis or other malignant conditions (4). Here, we report a case of Lennert's lymphoma mimicking tuberculous lymphadenitis on computed tomography (CT) images and pathologic findings.

A 70-year-old woman, who presented with palpable masses on the right neck, visited our institution. She had been experiencing pain on the right side of her neck for 3 weeks. All laboratory findings were within the normal limits (hemoglobin: 11.6 g/dL; hematocrit: 34.8%; red blood cell count: 3.06 × 10³/µL; white blood cell count: 6.69 × 10³/µL; and platelet count: 383 × 10³/µL). A physical examination revealed palpable and tender multifocal lumps. Percutaneous fine needle aspiration biopsy revealed reactive lymphoid cells on a histopathological examination. Neck, chest, and abdominal CT scans were obtained to evaluate nodal involvement. Neck and chest CT showed multiple enlarged lymph nodes in cervical, supraclavicular, and both axillary and mediastinal areas. Abdominal CT showed a heterogeneous enhancing mesenteric mass and multiple enlarged lymph nodes in the mesentery and both inguinal areas. Nodal involvement was most predominant in the cervical area. A chest CT showed no abnormalities in either lung. The tentative radiologic diagnoses were tuberculous or metastatic lymphadenopathy, because some of the nodal images showed central low attenuation with rim enhancement, which represents central necrosis (Fig. 1A-E). An excisional biopsy of the right neck nodes was performed under local anesthesia, and a diagnosis of tuberculous lymphadenitis was made because the lymph nodes showed chronic granulomatous inflammation with necrosis.

The patient took anti-tuberculosis drugs for 1 month; however, a follow-up CT showed disease progression. A second excisional biopsy was performed on the neck, and the histopathological analysis revealed chronic granulomatous inflammation with necrosis yet again. However, follow-up neck, chest, and abdominal CT scans showed disease progression despite additional anti-tuberculosis drug therapy for 2 months, so an excisional biopsy of the axillary lymph nodes was performed. The histopathology report obtained at that time showed malignant cells admixed with epithelioid histiocytes and inflammatory cells (Fig. 1F, G). The cells showed positive immunoreactivity for CD3 and CD4, focal positivity for CD30 and Ki-67, but no immunoreactivity for CD20, CD15, CD8, epithelial membrane antigen, or CD10. The cells showed negative results for both alpha fetoprotein and periodic acid Schiff staining.

A diagnosis of lymphoepithelioid lymphoma (Lennert's lymphoma) was made for all lymph nodes throughout the body by clinical, radiologic, and histopathologic findings, and we concluded that the granulomatous lesions in the previously obtained biopsy specimens were mistaken for tuberculous lymphadenitis by the pathologist.

The patient underwent chemotherapy for 2 months, and the follow-up CT revealed a marked decrease in both the size and extent of all the affected lymph nodes in cervical, supraclavicular, both axillary, mediastinal, mesenteric, and both inguinal areas, thereby suggesting improvement in the patient's condition.

Lymphoepithelioid lymphoma (Lennert's lymphoma) was first described by Lennert and Mestdagh (3) in 1968. It is characterized by a high concentration of epithelioid cells, the presence of an atypical variant of Hodgkin and Sternberg giant cells, and an abundance of plasmocytes. It was initially considered to be a variant of Hodgkin's disease (3). Lymphoepithelioid lymphoma has been regarded as a variant of malignant peripheral T-cell lymphoma (1) and is included as a peripheral T-cell lymphoma not otherwise specified (NOS) in the Revised European-American classification of lymphoid neoplasms and World Health Organization (2).

Lennert's lymphoma should not be confused with Lennert's pattern, which shows a diffuse scattered epithelioid population throughout the lymph node on histopathology. The following conditions are considered in a differential diagnosis with Lennert's pattern: granulomatous lymphadenitis, tuberculosis, sarcoidosis, abnormal immune response, peripheral T-cell lymphoma, T-cell rich B-cell lymphoma, mixed cellularity Hodgkin's lymphoma, nodular lymphocytic and histiocytic Hodgkin's lymphoma and lymphoepithelioma-like carcinoma. Lennert's lymphoma can be confused with all of these diseases, particularly when aggregates of epithelioid cells closely mimic granuloma, and can be mistaken as tuberculosis as in this case (4).

Dong et al. (5) reported six cases of non-Hodgkin's mesenteric lymphoma, which were of mixed homogenous and rim enhancing patterns. Mesenteric (Hodgkin's- and non-Hodgkin's-) lymphoma can be found as a solitary mass by fusion of multiple lymph nodes in most cases but can be by a single enlarged lymph node. Mesenteric lymphoma can also be found as multiple nodular or diffuse types (6). In our case, abdominal CT revealed one large mass type of mesenteric lymph node showing heterogeneous enhancement (Fig. 1D), and other multiple nodular mesenteric lymph nodes showing a homogenous enhancement pattern (Fig. 1E).

Choi et al. (7) reported CT findings with four enhancement patterns of peripheral T-cell lymphoma in the cervical area. Particularly, peripheral T-cell lymphoma NOS showed two enhancement patterns; 1) nodal necrosis, and 2) ill defined margin with heterogeneous enhancement. Cervical and thoracic lymph nodes in our case showed nodal necrosis or homogenous enhancement (Fig. 1A-C).

Low attenuated lesions on CT may represent necrosis or tumor replacement. Peripheral T-cell lymphomas first involve the marginal sinuses of the nodal cortex via afferent lymphatics and then invade the medulla. Proliferation of neoplastic cells results in blockage of the lymphatic flow and nodal necrosis (8).

The CT images in our case showed that the non-necrotic lymph nodes were much more numerous than the necrotic nodes. Non-necrotic lymph nodes showed homogenous enhancement and some mesenteric nodes encased mesenteric fat and vessels, which are typical findings of lymphoma (Fig. 1E) (9). However, the presence of some necrotic lymph nodes led us to misdiagnose tuberculous lymphadenitis. Radiologic reports of Lennert's lymphoma are extremely rare. Only one case describing the radiologic findings of Lennert's lymphoma has been reported in the English literature. In that report, the CT scan showed a large mesenteric mass with central calcification (10). The findings of that report were different from those of our case, which showed a large solid and necrotic mesenteric mass and other multiple small mesenteric lymph nodes.

This case is the first report of a CT finding of lymphoepithelioid cell lymphoma mimicking granulomatous lymphadenitis, presenting as a necrotic mesenteric mass and multiple lymph nodes with or without necrosis.

Here, we report a very rare and interesting case of lymphoepithelioid cell lymphoma with CT findings. Even though it is extremely rare, lymphoepithelioid cell lymphoma should be considered in the differential diagnosis of necrotic lymph nodes, particularly when combined with non-necrotic lymph nodes that show typical radiologic features of lymphoma.