DISCUSSION
While the local extension of hypopharyngeal and thyroid tumors to the larynx is common, metastatic laryngeal involvement remains rare; since fertile et al. in 1987, a 13 laryngeal metastasis was reported in the English literature from Colo-rectal cancer, and by Zenga et al. in 2016 colorectal was the most common primary site for laryngeal metastasis followed by renal and prostate cancer 6 cases each, then 5 cases of skin melanoma, the remaining cases were secondary to lung, bone, breast, thyroid, liver and female genital tract cancers. (3)
Trans-glottic glottic involvement was the most common compromising about 40% of the reported cases, followed by supraglottic area, then subglottic in less than 10% of the true vocal cords were involved, about 70% of the cases were reported in males, with the median age of 59 years, initial presentation in more than 60% was Dysphonia, the median time to laryngeal metastasis diagnosis was 3 years. (3)
The treatment modalities for secondary laryngeal metastasis vary depending on the stage of the disease, the number of the metastatic focus, and the involvement of other organs; in a case reported by Therasma et al. in 2008, the laryngeal metastasis was managed with organ preservation surgery as the patient was in remission from his primary cancer with no other organ involvement. (7) Another case by Marioni et al. was managed with total laryngectomy due to extensive laryngeal involvement, and local control was controlled at the time of laryngeal diagnosis. (8) Puxeddu et al., Sano et al., and Ta et al. managed their patients with a tracheostomy to protect the airway from local disease advancement. (9-11) In other cases, reported the local control of the disease was achieved by laser excision by Nd-YAG laser and CO2 Laser. (5, 12) Summary of laryngeal metastasis secondary to colorectal cancer is summarized in table 1.
Due to unfamiliarity with secondary laryngeal cancers, there is no census of the treatment guidelines; treatment options depend on the stage at the time of diagnosis, solitary laryngeal involvement, or the presence of other metastatic focus; however, it is thought that laryngeal cancer is still under-reported, as one post-mortem study reported by Prescher et al. showed laryngeal involvement in 6 autopsies out of 6 patients with prostate cancer and Horny and Kaiserling found 10 out of 14 patient with hematopoietic malignancy found to have laryngeal metastasis. (13, 14) Incidental laryngeal metastasis without symptoms is also evident, as reported by Xia et al. when a PET CT (positron emission tomography-computed scan) was done for an elevated AFP (Alfa fetoprotein) showed increased uptake in the larynx. (15)