Intestinal T-cell lymphoma: a reassessment of cytomorphological and phenotypic features in relation to patterns of small bowel remodelling.

Intestinal T-cell lymphoma (ITCL) is an uncommon entity among primary gastrointestinal lymphomas. In this study we evaluated tumours from 20 patients presenting with (n = 8) or without (n = 12) a history of coeliac disease (CD). Neoplastic lesions were composed of predominantly small (n = 4), small-to-medium (n = 2), medium/mixed-to-large (n = 7) or large and anaplastic (n = 7) cells. Different patterns of tumour growth and remodelling of the small bowel wall were observed. Pattern a (n = 4) was characterized by an intramucosal spread of small tumour cells with a small growth fraction. This pattern resembles mucosal inflammation in CD. In pattern b (n = 2), ulcerated solitary or multiple tumours composed of small to medium-sized cells were observed. The adjacent or distant mucosa showed a nearly normal architecture. In pattern c (n = 7), ulcerated lesions were composed of medium-sized to large cells. Mucosal flattening occurred in all segments infiltrated by lymphoma. In pattern d (n = 7), bowel remodelling was observed along the small intestine even at sites not affected by lymphoma. The main neoplastic lesions were composed of pleomorphic large or anaplastic cells frequently expressing the CD30 molecule. Intramucosal spread of a small epitheliotropic T-cell population was observed in the vicinity or even at distant segments of the small bowel. The demonstration of clonal rearrangements of T-cell receptor genes helped to trace widespread occurrence of this small intraepithelial neoplastic component. We suggest that different features of tumour cells such as the expression of activation antigens may contribute to the remodelling of small bowel mucosa. The addition of immunophenotyping data to macroscopic and microscopic features of specimens provided evidence that this uncommon lymphoma exhibits a spectrum in cytological composition and growth patterns. However, despite the considerable heterogeneity of the cases analysed, most of them shared a characteristic immunohistochemical profile (CD3+, CD8+/-, CD103+), further substantiating the view that ITCL is the neoplastic equivalent of an intraepithelial T-cell subset of the small intestine. This phenotype and the intraepithelial accumulation of lymphoma cells observed in the surviving mucosa are clues to the diagnosis of this clinicopathological lymphoma entity characterized by a broad range of morphological expressions.