ABSTRACT
<p><b>OBJECTIVE</b>To explore the regularity invading adjacent tissue of pyriform sinus carcinoma.</p><p><b>METHODS</b>The whole organ serial section of 68 total or partial laryngectomy and hypopharyngectomy specimen of pyriform sinus carcinoma were histopathologically studied.</p><p><b>RESULTS</b>In 68 pyriform sinus carcinoma, invaded ventricular and paraglottic spaces was 63 and 38 cases respectively, the difference of invasive frequency of both spaces was significantly marked (chi2 = 21.37, P < 0.01). Thyroid cartilage had the most invaded frequency of 92.6% (63/68). The all touching and pressing invasion of laryngeal cartilage was 89 times, and infiltrating invasion was 51 times. The invasive frequency of lateral cricoarytenoid muscle, posterior cricoarytenoid one, thyroarytenoid and interarytenoid ones were 63.2% (43/68), 57.4% (39/68), 55.9% (38/68), 51.5% (35/68) respectively. The invasive frequency of cricoarytenoid and cricothyroid joints were 30.9% (21/68), 17.6% (12/68) respectively. The invasive frequency of superior laryngeal nerve was 67.7% (44/65) , and more than that of recurrent laryngeal nerve (18/65, 27.7%). The pyriform sinus medial wall carcinoma was 14 cases, lateral wall carcinoma 18 cases, medial and lateral wall carcinoma 36 cases. The invaded pyriform sinus apex was 34 cases, normal its apex was 26 ones, submucous invasion of its apex was 8 ones. Light lymphocytic invasion was 66.2% (45/68) and seen most in pyriform sinus carcinoma. Submucous and leaping invasion of pyriform sinus carcinoma were 24 and 8 cases.</p><p><b>CONCLUSIONS</b>Intralaryngeal invasion of pyriform sinus carcinoma arose through paraglottic space first. Laryngeal cartilage membrane and their cartilage were anatomical obstacle against cancerous invasion. Lateral cricoarytenoid muscle, posterior cricoarytenoid one, thyroarytenoid and interarytenoid ones were often invaded. Pyriform sinus medial wall carcinoma invaded intralaryngeal structure easily, its lateral wall carcinoma may invade upward, downward and outward along thyroid cartilage interior wall, medial and lateral wall carcinoma may invade intralaryngeal and extralaryngeal structure, and was the most serious lesion. The invasion of pyriform sinus apex is an important sign of pyriform sinus carcinoma spreading downward to inferior and peripheral tissues of hypopharynx.</p>