T-cell / histiocyte-rich B cell lymphoma mimicking... : Indian Journal of Cancer (2024)

Sir,

T-cell / Histiocyte-rich large B-cell lymphoma (THRBCL) is characterized by a limited number of scattered, large, atypical B cells, embedded in a background of abundant T cells and frequently histiocytes.[¹] THRBCL has a histological similarity between nodular lymphocyte predominant Hodgkin's lymphoma (NLPHL) and classical Hodgkin's lymphoma (cHL).[²] THRBCL usually presents in a more advanced stage, with involvement of liver, spleen, and bone marrow in greater frequency.[¹²] We report nine cases of THRBCL diagnosed over a period of three years.

The cases were with age between 17 and 57 years, and eight were males. All presented with multiple cervical, axillary, and inguinal lymphadenopathy with hepatosplenomagaly. They had "B" symptoms and raised LDH levels. One case also had mediastinal lymphadenopathy. Six cases had advanced stage disease at presentation (three had bone marrow involvement, five had lung and / or pleural involvement). Five patients each had the international prognostic index (IPI) of 4 - 5 (high risk) and 3 (high intermediate) respectively, while one had IPI of 2 (low-intermediate), Median disease free survival after the start of treatment was 304 days (range: 30 - 870).

Immunohistochemical studies on lymph node biopsy specimens revealed a strong positive reaction for CD20 [Figure 1] and CD79a in all the cases, with 50 - 100% tumor cells showing a positive reaction. All patients were negative for CD15 [Table 1], while seven were positive for CD30 [Figure 2]. Three patients were positive for EBV and Bcl-2, while two were positive for Vimentin and EMA [Table 1]. The tumor cells showed CD 45 positivity. However, CD-45 positivity was difficult to evaluate, due to the positivity of the surrounding reactive lymphoid cells. The reactive cells were abundant and showed positivity for CD3 and CD45-RO. No rosette formation was seen around tumor cells with CD57. CD68 revealed a large number of histiocytes. A spherical meshwork of follicular dendritic cells was not seen with CD35.

Tumor cells of THRBCL always show positivity to CD45 and CD20 and usually to CD79α, and negative reaction to CD15, CD30, EBV, and Vimentin.[³⁴⁵] In our case-series, seven cases showed positivity for CD30 (CD30 positive giant cells had RS cell-like morphology), of which three were positive for EBV and two for Vimentin, suggesting a probable association with cHL-like phenotype. However, CD45 positivity and CD15 negativity in all cases argues against the diagnosis of cHL. Neoplastic cells in two cases co-expressed EMA and CD30, showing a closer association with NLPHL.[⁴⁵] CD57 positive rosettes around neoplastic cells in the background is characteristic of NLPHL. Absence of CD57 + rosettes in all the cases argues against the diagnosis of NLPHL.[²]

In conclusion, a small percentage of tumor cells of THRBCL showing features closely resembling classic Hodgkin's lymphoma as well as NLPHL probably suggest a biological overlap or "gray zone" between these entities. As the clinical behavior, management, and prognosis of THRBCL is different from other lymphoid malignancies, a detailed morphological and immunophenotypical analysis is essential, to distinguish it from NLPHL and c-HL.

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