Immunohistochemical assessment of the diagnostic utility of PD-L1: a preliminary analysis of anti-PD-L1 antibody (SP142) for lymphoproliferative diseases with tumour and non-malignant Hodgkin-Reed-Sternberg (HRS)-like cells.

AIMS: The programmed death 1 (PD1)/PD1 ligand (PD-L1) axis plays an important role in tumour cells escape from immune control. PD-L1 immunohistochemistry is a useful predictor of immunotherapy response, but is still not used widely in the diagnostic setting. Here we describe results using PD-L1 immunohistochemistry during routine diagnostics in lymphoma. METHODS AND RESULTS: Ninety-one lymphoproliferative disease cases sharing tumour and non-malignant Hodgkin-Reed-Sternberg (HRS)-like cells with and without Epstein-Barr virus (EBV) association were investigated by immunohistochemistry for PD-L1 (clone SP142). PD-L1 expression was present in more than 5% of tumour or non-malignant HRS-like cells in 100% of EBV+ classical (C) Hodgkin lymphoma (HL) (n = 10) and EBV-negative nodular sclerosis CHL (n = 8); 40% of EBV+ diffuse large B cell lymphoma, not otherwise specified (DLBCL-NOS) (n = 20); and 4% of nodal peripheral T cell lymphoma of follicular helper T cell type (PTCL-TFH) (n = 22). In contrast, nodular lymphocyte-predominant HL (n = 4), lymphocyte-rich CHL (n = 6), EBV+ hyperplasia (n = 8), plasmablastic lymphoma (n = 3) and anaplastic lymphoma kinase-negative anaplastic large cell lymphoma (n = 5) seldom exhibited PD-L1 in their large cells. Assessing PD-L1 positivity in tumour and non-malignant large cells was helpful in differentiating between CHL versus nodal PTCL-TFH (P < 0.0001) or EBV+ DLBCL-NOS (P = 0.0052) and between EBV+ DLBCL-NOS versus nodal PTCL-TFH (P = 0.0052), with PD-L1 expression indicating the first diagnosis in each of those sets. CONCLUSION: Immunohistochemical evaluation of PD-L1 expression in tumour and non-malignant HRS-like large cells may be useful for assessing either immune escape or immunodeficiency in their pathogenesis.

Mucosa-associated lymphoid tissue lymphoma with large cell transformation on the background of Hashimoto's thyroiditis: a case report and review literature.

Primary thyroid lymphoma (PTL) is a rare cause of malignancy that occurs in 0.5% of cases with Hashimoto's thyroiditis. The most common subtype is diffuse large B-cell lymphoma (DLBCL), followed by mucosa-associated lymphoid tissue (MALT) lymphoma. We described the case of a 70-year-old man who was diagnosed with MALT lymphoma in the background of autoimmune thyroiditis with focal area of DLBCL transformation. The patient was a 70-year-old man with rapidly growing mass of the thyroid gland with compressive symptom over two months. The laboratory data revealed primary hypothyroidism with positively anti-thyroid antibodies. The computerized tomography scan showed right thyroid mass extended to anterior mediastinum and compressed adjacent airway with multiple cervical and mediastinal lymphadenopathies. The pathology from incisional biopsy showed extranodal marginal zone B-cell lymphoma of MALT lymphoma with large cell transformation. The patient received four courses of systemic chemotherapy combined with involved field radiation therapy. The mass was dramatically decreased in size after treatment, leading to a complete resolution of compressive symptoms. Thyroid lymphoma is quite rare; however the incidence may be higher in patients with Hashimoto's thyroiditis. A rapidly growing thyroid gland should be considered as PTL. Chemotherapy and radiation are the mainstays of treatment.