Angulated Giant Cell with Clefting: A Clue to the Diagnostic Dilemma of Nodular Tenosynovitis

Nodular Tenosynovitis (NTS) is a fairly common soft tissue lesion, often diagnosed as benign lesion clinically. Occasionally these, especially the recurrent lesions may mimic a malignant tumor, clinically and to a certain extent histologically. To highlight the characteristic morphological features especially of the angulated and kite shaped giant cells with clefting and review the probable histiogenesis. Twenty one cases of NTS encountered in our centre over a period of 7 years including two recurrent lesions, closely mimicking melanoma and Malignant Fibrous Histiocytoma (MFH) were included in the study. Characteristic histological features with special attention to the morphology of the giant cells were observed and studied. These tumors are fairly easily recognisable histologically. The variable histomorphological features are described and those of diagnostic help highlighted, especially when one come across a highly cellular recurrent lesion mimicking malignancy. We have observed that giant cells are sparse in some tumors. When present, they are not the classical osteoclastic type, having fewer nuclei (average: 13). They have a peculiar angulated rather than smooth rounded border (64% angulated) with cleftin. (88% clefted). Awareness of the typical presentation, location and characteristic morphology should make the lesion easily recognizable. In a typical or recurrent lesions, a careful search for the sparsely distributed giant cell with a peculiar shape, presence of foamy histiocytes and iron demonstrable with a simple iron stain can resolve the dilemma, if any.