Answer: Inflammatory myofibroblastic tumor

Histology: The tumor consists of a proliferation of spindled cells centered in the laryngeal submucosa. The spindled cells are arranged in a haphazard pattern, are separated by bands of collagen, and possess open chromatin and prominent nucleoli. There is a sprinkling of small lymphocytes throughout. Mitotic activity is low, and necrosis is absent. The tumor was positive for actin and ALK-1, and negative for cytokeratins, desmin, and p40.

Discussion: When approaching mucosal based spindle cell lesions of the head and neck, the number one consideration should be spindle cell carcinoma. However, in this case the absence of surface dysplasia, cytokeratin/p40 immunostaining, or overtly malignant histologic features make the diagnosis of spindle cell carcinoma unlikely. In this case, the relatively bland cytologic features and sparse inflammatory infiltrate prompted us to perform at ALK-1 immunostain, which confirmed the diagnosis of inflammatory myofibroblastic tumor (IMT).

IMT was originally thought to be a reactive, non-neoplastic mesenchymal proliferation, but molecular studies have revealed ALK rearrangement in a subset suggesting that at least some are neoplastic. IMTs of the head and neck are uncommon, and usually present in the larynx as polypoid mucosal masses. The morphologic features of head and neck IMT are similar to those seen in other sites: variably myxoid to fibrous, with “tissue culture” like myofibroblasts in short fascicles and varying degrees of inflammation. ALK-1 immunostaining is very helpful when positive; FISH for ALK rearrangements can also be employed. IMTs of the head and neck usually behave in a benign fashion, but atypical histologic features (e.g., necrosis, mitoses, pleomorphism) may predict more aggressive behavior.

Reference(s):
– Wenig BM, et al. Cancer. 1995;76(11):2217-29.
– Coffin CM, et al. Am J Surg Pathol. 2007;31(4):509-20.