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13 November 2013 - Case of the Week #291

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Thanks to Mitra Mehrad, M.D., Barnes-Jewish Hospital, Missouri (USA) for contributing this case. To contribute a Case of the Week, follow the guidelines on our Case of the Week page.


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Case of the Week #291

Clinical History:
A 47 year old woman with sinusitis and nasal polyps underwent endoscopic sinus surgery.

Micro images:

What is your diagnosis?

Nasal chondromesenchymal hamartoma

Nasal chondromesenchymal hamartoma is a rare, often cystic lesion that typically fills the nasal cavity and extends into the ethmoid sinuses. It was first reported in 1998 at Barnes-Jewish Hospital (Am J Surg Pathol 1998;22:425), where this Case of the Week originated. It is considered an upper respiratory tract analogue of chest wall mesenchymal hamartoma. Although benign, it may erode the cribriform plate, and have an intracranial component. It is more common in males (2/3), and typically affects children, with a mean age of 14 months. Reports in adults are uncommon (Arch Pathol Lab Med 2005;129:1444). It is occasionally associated with pleuropulmonary blastoma (Int J Pediatr Otorhinolaryngol 2010;74:1240).

Histologically, as in this case, there is well demarcated mature cartilage, myxoid stroma and spindle cells. There may also be focal osteoclast-like giant cells, aneurysmal bone cyst-like formations, and collagen fibers (Arch Pathol Lab Med 2001;125:400). Electron microscopy shows fibroblastic and myofibroblastic differentiation.

The differential diagnosis includes:

Aneurysmal bone cyst: uncommon in nasal cavity; grows rapidly at other sites; expanding osteolytic lesion of blood-filled spaces of variable size separated by connective tissue septa with osteoclast giant cells and variable reactive bone; typically no cartilage, prominent giant cells with 10-20 nuclei that aggregate in groups of 6-12 cells; also metaplastic woven bone and lamellar bone lined by osteoblasts and occasionally osteoclasts
Chondroblastoma: typically teenage boys with epiphyseal tumor
Chondromyxoid fibroma: ages 15-25, affects metaphysis of long tubular bones, small bones of feet or any bone, skull base; atypia is common, including large, hyperchromatic nuclei
Fibrous dysplasia: medulla of diaphysis or metaphysis of craniofacial bones, femur, ribs are most common; mean age 32 years; curvilinear trabeculae (Chinese letters) of metaplastic woven bone (never matures) in hypocellular, fibroblastic stroma
Osteochondromyxoma: also occurs in nasal region; sheets and lobules of bland cells in myxomatous, cartilaginous, osseous, and hyaline fibrous matrix; erodes bone and frequently extends into soft tissue; lacks giant cells and aneurysmal bone cyst-type reaction

Surgical resection is usually curative, although it may be technically difficult because of the extent of disease. The first case of malignant transformation was recently reported (Histol Histopathol 2013;28:337).

Nat Pernick, M.D., President
and Palak Thakore, Associate Medical Editor
PathologyOutlines.com, Inc.
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