Sinonasal Tract Osteochondromyxoma: An Underrecognized Tumor Easily Mistaken for Nasal Chondromesenchymal Hamartoma.

Introduction: Matrix-producing tumors of the sinonasal region are diagnostically challenging, with a large number of similar-appearing neoplasms having different prognoses, treatment strategies, and genetic syndrome associations. Osteochondromyxoma (OCM) is a very rare tumor known to be associated with Carney complex. Since its initial description in 2001, fewer than 20 cases have been reported, with the sinonasal tract being an apparently favored site. Herein we describe 6 new cases of sinonasal OCM.

Methods: OCM cases with available slides were retrieved from the surgical pathology files of the authors' practices.

Results: The tumors arose in 4 boys and 2 girls, ranging from 4 to 17 years (mean, 9.5 years). All presented with nasal obstruction and a mass. Radiologically the tumors presented as indolent-appearing, heterogeneous, calcified, expansile masses. Histologically the tumors all consisted of bland, normochromatic spindled to stellate cells in a myxoid to collagenized stroma, with variable amounts of cartilage and bone formation. Mitotic activity was very low and necrosis was absent. All demonstrated complete loss of PRKAR1A expression by immunohistochemistry. Of these 6 cases, 3 had been originally diagnosed as nasal chondromesenchymal hamartomas, and one as osteosarcoma. Treatment and follow up information were available for 5 patients: all were treated with surgery, with one also receiving chemotherapy after an initial osteosarcoma diagnosis. At the time of last clinical follow-up, all 5 patients were alive, one with residual disease. No patient was known to have other stigmata of Carney complex.

Conclusions: Although rare, OCM preferentially occurs in the sinonasal tract, and therefore may be encountered by head and neck pathologists. Given their predilection for young patients and overlapping morphologic features, OCM are easily misdiagnosed as other matrix-forming sinonasal tumors, especially nasal chondromesenchymal hamartoma. Immunohistochemical demonstration of PRKAR1A loss is valuable for confirming an OCM diagnosis, which should prompt clinical investigation for the possibility of Carney complex.