Bacterial lymphadenitis with the picture of a lymphoepithelioid cell lymphoma--Lennert's lymphoma

Revising the historical collection of epithelioid cell-rich lymphomas of the Kiel Lymph Node Registry: what is Lennert's lymphoma nowadays?

AIMS

Lennert's lymphoma is a rare variant of peripheral T-cell lymphoma (PTCL) not otherwise specified (NOS). The aim of this study was to further characterize this tumour.

METHODS AND RESULTS

Historical material of 97 lymphomas with a high content of epithelioid cells, collected at the Kiel Lymph Node Registry were reviewed, by applying immunohistochemistry and current diagnostic criteria. Among all cases revised, various B-cell lymphoma entities (25 cases), Hodgkin lymphomas (21 cases) and PTCL subtypes (48 cases) could be identified. A distinctive subgroup of eight PTCLs was found that were regarded as genuine Lennert's lymphomas. These cases were characterized by mild atypia, a non-activated cytotoxic phenotype [TIA1 cytotoxic granule-associated RNA binding protein (TIA1)-positive(+) and granzyme B-negative], and a substantial lack of follicular T-helper (T(FH) ) cell markers. Among the other PTCLs, including angioimmunoblastic T-cell lymphoma and PTCL NOS, many cases with positivity for more than three T(FH) cell-associated molecules were recorded.

CONCLUSIONS

Our study shows that, according to current criteria, Lennert's lymphoma is a rare but distinctive entity among epithelioid cell-rich lymphomas, differing on grounds of morphology and immunophenotype from other PTCL subtypes. An additional finding is the broad morphological spectrum of epithelioid-cell rich PTCLs showing a T(FH) cell phenotype.

Systemic Mycobacterium kansasii infection mimicking peripheral T-cell lymphoma

Nontuberculous mycobacteria are opportunistic pathogens which predominantly infect the immunocompromised host. The clinical and pathologic diagnosis of mycobacterial infection is generally not difficult. However, it may mimic malignancy on account of the clinical manifestations or the morphology of atypical lymphocytes with epithelioid histiocytes. The latter can be found in some types of lymphomas, especially T-cell lymphoma. This report describes two immunocompetent patients with systemic Mycobacterium kansasii infection presenting with fever, systemic lymphadenopathy, and osteolytic bone lesions. The microscopic features of these two cases were similar and were characterized by effacement of the nodal architecture by lymphocytic infiltrates and small aggregates of epithelioid histiocytes throughout. These lymphocytes showed mild atypia and expressed predominantly CD3. Bone marrow was also involved in the same process in one case and T-cell lymphoma with lymphoepithelioid features was the initial impression. However, further studies reported germline arrangements of T-cell receptor genes, presence of acid-fast bacilli, and recovery of M. kansasii in culture. At follow-up, the lymphadenopathy was seen to have disappeared during antimycobacterial treatment. This report describes two infectious cases with small aggregates of epithelioid histiocytes and atypical lymphocytes mimicking peripheral T-cell lymphoma; and such cases may become more common as the number of immunosuppressed hosts is increasing worldwide. We have reviewed the literature and summarized useful morphologic criteria for differentiation.

Granulomatous mycosis fungoides: report of a case with some histopathologic features of granulomatous slack skin

We describe a case of granulomatous mycosis fungoides, tumor stage, mimicking sarcoidosis in an 82-year-old man with a 2-year history of skin disease. The final diagnosis was established after one of seven biopsy specimens showed a nongranulomatous histologic picture of patch-stage mycosis fungoides. Monoclonality was proven for the lymphocytic population by T-cell-receptor rearrangement studies. The unusually extensive granulomatous inflammation with huge giant cells surrounded by CD1a-positive cells in the other six biopsy specimens was suggestive of the histopathology of granulomatous slack skin, another rare granulomatous cutaneous T-cell lymphoma. Because both a clinical and histologic overlap between granulomatous mycosis fungoides and granulomatous slack skin have been reported in the literature, we conclude that they may belong to the spectrum of a single disease.