结节病是马常见的间叶性肿瘤。尽管很少有研究对结节病进行长期随访，但结节病被认为是局部侵袭性的，并且据报道在手术切除后经常复发。目前，尚未确定组织学特征来预测哪些结节病在切除后会复发。本研究包括 49 个结节病，这些结节病具有组织学切片并且已知病例的复发状态。每个肉瘤都是从不同的马身上切除的。总体而言，49 个结节病中有 12 个 (24%) 在手术切除后复发。对有丝分裂计数（MC）、细胞结构、坏死、核多形性和肉瘤炎症进行组织学评估。其中，MC 与复发相关。 2.37 mm2 中，MC ≥ 20 的 5 个结节中有 4 个 (80%) 复发，复发率明显高于 MC < 20 的结节，44 个病例中有 8 个复发 (18%)，P = .0051。还发现临床类型与复发相关。 4 种成纤维细胞类型中的 3 种（75%）复发，其复发率显着高于其他临床类型的肉瘤，45 例中有 9 例（18%），P < .001。此外，单变量 Cox 回归分析证实成纤维细胞类型和 MC ≥ 20 是复发的显着预测因子（分别为 P = .016 和 P = .005）。据作者所知，这是第一个检查结节病复发率的大型研究，也是第一次将组织学特征与复发相关联。

Sarcoids are common mesenchymal neoplasms of horses. Although there are few studies in which sarcoids have been followed over a long period of time, sarcoids are considered locally invasive and have been reported to frequently recur following surgical excision. Currently, no histological features have been identified to predict which sarcoids will recur after excision. The present study comprised 49 sarcoids for which histology sections were available and in which the recurrence status of the case was known. Each sarcoid was excised from a different horse. Overall, 12 of the 49 (24%) sarcoids recurred after surgical excision. Mitotic count (MC), cellularity, necrosis, nuclear pleomorphism, and inflammation of the sarcoids were evaluated histologically. Of these, MC correlated with recurrence. Four of 5 (80%) sarcoids with an MC ≥ 20 in 2.37 mm2 recurred, which was a significantly higher recurrence rate than that of sarcoids with an MC < 20, 8 of 44 cases recurred (18%), P = .0051. Clinical type was also found to correlate with recurrence. Three of 4 (75%) fibroblastic types recurred, which was a significantly higher recurrence rate than that of sarcoids with other clinical types, 9 of 45 cases (18%), P < .001. In addition, univariate Cox regression analysis confirmed fibroblastic type and MC ≥ 20 as significant predictors for recurrence (P = .016 and P = .005, respectively). To the authors' knowledge, this is the first large study examining recurrence rates in sarcoids, and the first time that histological features have been correlated with recurrence.