Nasal Chondromesenchymal Hamartoma: Rare Case Report in an Elderly Patient and Brief Review of Literature

Hamartomas are considered a mixture of nonneoplastic tissue, which may be indigenous to a different location in the body. As such, they may be epithelial, mesenchymal, or mixed. In the sinonasal region, the following hamartomatous lesions are considered to lie on a spectrum and include respiratory epithelial adenomatoid hamartoma (REAH), chondro-osseous respiratory epithelial adenomatoid hamartoma (COREAH), and nasal chondromesenchymal hamartoma (NCMH). To our knowledge, less than 50 cases of sinonasal hamartomas have been reported in the English literature so far with NCMH being very rare and primarily a tumor in infancy, with only 2 cases reported in individuals older than 16 years of age. We report a highly unusual case of a NCMH in the right maxillary sinus of a 70-year-old female.


Case Report
A 70-year-old female presented with a two-year history of slowly growing, nonpainful maxillary sinus mass. She has a history of chronic maxillary sinusitis corresponding to presentation of the mass, with the first episode reported in 2014. Computed tomography (CT) imaging revealed an erosive right maxillary sinus mass (2.5 x 2.1 cm) with bony destruction.
Surgical excision of the right maxillary sinus mass revealed a fragmented, white, vaguely nodular, and whorled lesion. Histological examination revealed fragments of respiratory-type epithelium with focal cystic invagination and associated squamous metaplasia [ Figure 1]. The underlying stroma consisted of a variably cellular, benign spindle cell proliferation with an associated background of hyalinization [ Figure 2], calcification and ossification [ Figure 3], and focal chondroid change [ Figure 4] in a vague lobule-like arrangement. Focal areas of aneurysmal and cystic changes [ Figure 5] were seen which would provide an explanation for the clinically noted enlargement since hamartomas by definition would be expected to have a much lower rate of growth. The intrinsic slow-growing nature is also supported by the deficit of mitotic activity even in the highly cellular/spindled regions of the lesion (less than 1/10 hpf). Areas with haphazard arrangement of nerve bundles within the collagenous stroma [ Figure 6] were also noted. Immunohistochemical stains were positive for SMA [Figures 7(a) and 7(b)] in the spindle cells and negative for CK AE1/AE3, EMA, CD34, Stat6, ERG/FLI-1, Mucin 4, S-100, Sox-10, and desmin [ Figure 8] ; ruling out perineurioma, solitary fibrous tumor, a vascular neoplasm, Evans tumor, a benign peripheral nerve sheath tumor, or a myogenic neoplasm. The overall findings were suggestive of a hamartomatous lesion, most likely a nasal chondromesenchymal hamartoma. The absence of submucosal glandular proliferation, myxoid stroma, or mucinous metaplasia in the lining epithelium lowers the likelihood of other neoplastic hamartomatous lesions such as COREAH.

Discussion
Nasal chondromesenchymal hamartomas are most commonly seen in the nasal cavity of children less than 3 months old, with less common involvement of the paranasal sinuses [2]. As per one review [1], mean age for NCMH was 9.6 years. Review of the English PubMed literature reveals 43 cases [ Table 1] of NCMH previously published, with our case being 2 Case Reports in Pathology

PanCk (5x)
Desmin (5x) Sox-10 (40x) ERG/FLI-1 (5x) CD34 (5x) S100 (40x) Figure 8: Lesional cells are negative for pan-cytokeratin (ae1/ae3), desmin, Sox-10, and S100. CD34 and ERG/FLI-1 highlight vascular endothelial cells.  the oldest patient reported, and presenting with a tumor in an unusual location. Our case would lend support to extending the age range for NCMH and considering it in the differential diagnosis of all sinonasal region tumors, irrespective of age, and location in the head and neck region. Despite primarily being a benign lesion, these tumors can present with areas of necrosis and local destruction, including bony invasion. The tumors can be aggressive appearing on imaging, extending into bony structures, including the cranium and/or the orbital cavity, which should not lead away from the diagnosis of this benign lesion. Detailed CT or preferably MRI prior to surgical excision should be performed.
NCMH has been associated with development of pleuropulmonary blastoma (PPB) during infancy. A recent [28] report highlighted the association of NCMH and PPB with DICER1 mutation and various associated entities such as lung cysts, cystic nephroma, renal sarcoma, Wilms tumor, thyroid hyperplasia, and CNS tumors. NCMH in isolation however is a benign lesion with follow-up in patients up to 16 years after excision, except for one reported case with malignant transformation in the literature [20]. Etiologically, it would make sense that cases in adults, such as ours, represent a tissue response to insult, such as chronic sinusitis rather than an inborn germline error (such as a DICER1 mutation).
Whether the presentation of a NCMH at a later age predisposes to malignant transformation due to the longstanding nature of the lesion is up for debate. It could represent a somatic DICER1 mutation rather than a germline mutation, causing the hamartoma to form later in age. Longer follow-up results from the adult cases and routine genetic testing in all NCMH will help provide an answer to these questions.

Conclusion
We report an unusual case of NCMH eroding the right maxillary sinus of a 70-year-old female. Although, NCMH is a rare entity with predilection for pediatric age groups, it is important to consider NCMH in the differential diagnosis of nasal/sinonasal masses in adult patients in order to avoid diagnostic errors.